ALBERT

Description:    Using short-term treatments, the aim of this study was to analyze the role of hydrogen peroxide in the regulation of AAO activity during Cd, Cu or IAA treatments in barley root tips. For analysis individual barley root segments were obtained by the gradual cutting of each root from the tip to the base 1, 2, 3 or 6 h after short-term treatments. Already a short 30 min exposure of barley roots to Cd induced significant root growth inhibition in a Cd concentration dependent manner, which was accompanied by a marked reduction of AAO activity. At Cu concentration which had no effect on the root growth a significant increase in AAO activity was observed. This increased AAO activity was detected only in ionically-bound CW fraction. In contrast, Cu at higher concentration and IAA inhibited both ionically-bound CW AAO isozymes. Prompt inhibition of AAO activity immediately after short-term treatment was observed only in the case of H 2 O 2 treatment suggesting that H 2 O 2 may act as an inhibitor of AAO. This was further supported by the observation that all Cd-, Cu- or IAA-induced root growth and AAO activity inhibition in barley roots was connected with an elevated production of H 2 O 2 . Content Type Journal Article Pages 1-9 DOI 10.1007/s11104-011-0869-9 Authors Veronika Zelinová, Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523 Bratislava, Slovak Republic Ľubica Halušková, Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523 Bratislava, Slovak Republic Igor Mistrík, Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523 Bratislava, Slovak Republic Ladislav Tamás, Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523 Bratislava, Slovak Republic Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    It is known that the number of limiting nutrients may affect the species richness of plant communities, but it is unclear whether the type of nutrient limitation is also important. I place the results from a study in Patagonia (elsewhere in this issue) in the context of the number and types of nutrients that are limiting. I present four mechanisms through which N or P limitation may potentially influence species richness. These mechanisms are related to: (i) the number of forms in which P or N are present in soil and the plant traits needed to acquire them, (ii) the mechanisms and traits that control species competition and coexistence under N or P limitation, (iii) the regional species pools of plants capable of growing under N- and P-limited conditions, and (iv) the interaction between the type of nutrient limitation and community productivity. It appears likely that P limitation can favour a higher species richness than N limitation, in at least in a variety of low productive plant communities, but evidence to support this conclusion is so far lacking. The four mechanisms proposed here offer a framework for exploring whether the type of nutrient limitation per se, or an interaction with productivity, is a potential driver for variation in species diversity. Content Type Journal Article Pages 1-9 DOI 10.1007/s11104-011-0796-9 Authors Harry Olde Venterink, Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092 Zurich, Switzerland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims In a previous study, a compost water extract (CWE) applied to pea seedlings resulted in 〉95 % protection against root infection. The protection was correlated with retention of a sheath of root border cells surrounding each root tip. A transient exposure to CWE was correlated with 80 % reduction in infection, and with retention of border cell sheaths. Early effects of CWE on border cell dispersal therefore were examined. Materials and methods Temporal and spatial dynamics of pea, maize, cotton, and cucumber border cell dispersal into water or CWE were measured. Results Border cells formed a mass surrounding root tips within seconds after exposure to water, and most cells dispersed into suspension spontaneously. In CWE, 〉90 % of the border cell population instead remained appressed to the root surface, even after vigorous agitation. In cotton, for example, 〉25,000 border cells dispersed within seconds of immersion in water, but 〈100 border cells dispersed after 〉24 h in CWE. Conclusions Border cells can contribute 〉90 % of carbon released from young roots, and a single border cell can trap hundreds of bacteria within minutes. The impact of altered border cell dispersal on soil properties, plant nutrition, and root disease development warrants further study.

Description: Background and aims The objectives of this study were to elucidate the mechanisms of interaction between root exudates of tall fescue and functional bacteria associated with petroleum degradation and whether components of the exudates can enhance petroleum removal from soil. Methods Root exudates of tall fescue were collected through a continuous root exudate trapping system and identified by GC-MS. Chemotaxis, swarming, and in vitro assay were conducted to assess the effects of the organic acids of root exudates on Klebsiella sp. D5A (plant growth promoting rhizobacterium), Pseudomonas sp. SB (biosurfactant producing bacterium), and Streptomyces sp. KT (petroleum-degrading bacterium). A pot experiment with organic acid amendment was conducted to study the effects of these components of root exudates on petroleum remediation. Microbial physiological metabolisms affected by organic acids were tested using Biolog Eco plates. Results Palmitic acid was found to be most effective in promoting D5A colonization on tall fescue. ρ-Hydroxybenzoic and palmitic acids significantly stimulated the growth of strains D5A, SB, and KT. Furthermore, palmitic acid amendment significantly enhanced petroleum removal in pot experiment. Conclusions Palmitic acid was the critical organic acid to facilitate petroleum removal during phytoremediation. These findings provide insight into the mechanisms by which tall fescue enhances the degradation of petroleum.

Description: Aims Leaf and root phenology play important roles controlling plant productivity and ecosystem function, yet, few studies link patterns of leaf and root phenology across woody species. Trees with diffuse-porous wood anatomy tend to leaf-out before ring-porous species and we expected that increases in transpiration with spring leaf-out would be coupled with initiation of root production to support uptake of soil resources. Therefore, we hypothesized that the timing of root production would follow patterns of leaf production and wood anatomy. Methods Root production was observed using minirhizotrons and related to leaf phenology across six temperate tree species with different wood anatomy in a common garden. Results As expected, leaves of diffuse-porous species emerged before ring-porous, followed by tracheid species. Root production peaked before bud break in five of the six species and before maximum leaf area index in all species, but did not follow expected patterns with leaf production. Conclusions Our observations did not indicate tight linkages between root and leaf phenology but do highlight the potential for very early season root production and greater variation in the phenology of roots than leaves. Future work should identify the environmental factors and species traits that best explain variation in root phenology.

Description:    Ammonia (NH 3 ) fluxes between beech leaves ( Fagus sylvatica ) and the atmosphere were investigated in a 90-year-old forest canopy and related to leaf nitrogen (N) pools and glutamine synthetase (GS) activities. The stomatal ammonia compensation point, χ NH 3 , was measured by both a twig cuvette and bioassay techniques involving measurements of pH and ammonium (NH 4 + ) concentration in the leaf apoplastic solution. The χ NH 3 determined on the basis of the gas exchange measurements followed a seasonal variation with early-season peaks during leaf expansion (9.6 nmol NH 3 mol −1 air) and late-season peaks during leaf senescence (7.3 nmol NH 3 mol −1 air). In the mid-season, the χ NH 3 of mature green leaves was much lower (around 3 nmol NH 3 mol −1 air) and dropped below the NH 3 concentration in the ambient atmosphere. For comparison, χ NH 3 obtained by the apoplastic bioassay were 7.0, 3.7 and 6.4 nmol NH 3 mol −1 air in early-, mid-, and late -season, thus agreeing reasonably well with χ NH 3 values derived from the gas exchange measurements. Potential NH 3 emission fluxes during early and late season were 1.31 and 0.51 nmol m −2 leaf surface area s −1 , respectively, while leaves were a sink for NH 3 during mid-season. During leaf establishment and senescence, both apoplastic and bulk tissue NH 4 + concentrations were relatively high coinciding with low activities of glutamine synthetase, which is a key enzyme in leaf N metabolism. In conclusion, the exchange of NH 3 between beech leaves and the atmosphere followed a seasonal variation with NH 3 emission peaks being related to N mobilization during early leaf establishment and remobilization during late leaf senescence. Content Type Journal Article Pages 1-16 DOI 10.1007/s11104-010-0693-7 Authors Liang Wang, Plant and Soil Science Section, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen Denmark Yingchun Xu, Plant and Soil Science Section, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen Denmark Jan Kofod Schjoerring, Plant and Soil Science Section, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen Denmark Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Boron (B) deficiency depresses wheat, barley and triticale yield through male sterility. On the basis of field responses to B fertilization, maize ( Zea mays L.) is affected by B deficiency in five continents. In a series of sand culture trials with maize subject to B0 (nil added B) and B20 (20 μM added B) treatments, we described how B deficiency depressed maize grain yield while showing an imperceptible effect on vegetative dry weight. With manual application of pollen to the silk of each plant, B0 plants produced 0.4 grain ear −1 compared with 410 grains ear −1 in B20 plants. Symptoms of B deficiency was observed only in B0 plants, which exhibited symptoms of narrow white to transparent lengthwise streaks on leaves, multiple but small and abnormal ears with very short silk, small tassels with some branches emerging dead, and small, shrivelled anthers devoid of pollen. Tassels, silk and pollen of B0 plants contained only 3–4 mg B kg −1 DW compared with twice or more B in these reproductive tissues in B20 plants. A cross-fertilization experiment showed that, although the tassels and pollen were more affected, the silk was more sensitive to B deficiency. Pollen from B20 plants applied to B0 silk produced almost no grains, while pollen from B0 on B20 silk increased the number of grains to 37% of the 452 grains plant −1 produced from B20 pollen on B20 silk. Therefore, the silk of the first ear may be targeted for precise diagnosis of B status at maize reproduction, for timely correction by foliar B application, and even for B-efficient genotype selection. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-010-0685-7 Authors Sittichai Lordkaew, Multiple Cropping Center, Faculty of Agriculture, Chiang Mai University, Chiang Mai, 50200 Thailand Bernard Dell, Sustainable Ecosystem Research Institute, Murdoch University, Perth, 6150 Australia Sansanee Jamjod, Department of Plant Science and Natural Resources, Faculty of Agriculture, Chiang Mai University, Chiang Mai, 50200 Thailand Benjavan Rerkasem, Department of Plant Science and Natural Resources, Faculty of Agriculture, Chiang Mai University, Chiang Mai, 50200 Thailand Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Oxidation by soil bacteria is the only biological sink for atmospheric methane (CH 4 ). There are substantial uncertainties regarding the global size of this sink, in part because the ecological controls of the involved processes are not well understood to date. We have investigated effects of severe summer drought and of nitrogen inputs (ammonium nitrate or cattle urine) on soil CH 4 fluxes in a field experiment. Soil moisture was the most important factor regulating the temporal dynamics of CH 4 fluxes. Simulated drought episodes altered the soil’s water balance throughout the year, increasing CH 4 oxidation by 50% on an annual basis. N fertilizers exerted only small and transient effects at the ecosystem level. Laboratory incubations suggested that effects differed between soil layers, with larger effects of drought and N application in the top soil than in deeper layers. With soil moisture being the primary controlling factor of methanotrophy, a detailed understanding of the ecosystem’s water balance is required to predict CH 4 budgets under future climatic conditions. Content Type Journal Article Pages 1-11 DOI 10.1007/s11104-010-0690-x Authors Adrian A. Hartmann, Institute of Plant, Animal and Agroecosystem Sciences, ETH Zurich, Universitätsstr. 2, 8092 Zurich, Switzerland Nina Buchmann, Institute of Plant, Animal and Agroecosystem Sciences, ETH Zurich, Universitätsstr. 2, 8092 Zurich, Switzerland Pascal A. Niklaus, Institute of Plant, Animal and Agroecosystem Sciences, ETH Zurich, Universitätsstr. 2, 8092 Zurich, Switzerland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Phosphorus (P) loss from land can impair surface water quality. Losses can occur from soil and plant components. While it is known that P losses increase with soil P concentration, it is not known how losses from pasture plants vary with soil P concentration or between different forages. We examined total P and filterable reactive P (FRP) in water extracts of plant shoots, used as a measure of potential P loss to surface runoff, in different forage species relative to soil P concentration in field trials and a glasshouse experiment. The mean total P concentration of 16 forage species in grazed field plots was greater ( P  〈 0.01; LSD 05  = 117 mg kg −1 ) in legumes (3,480 mg kg −1 ) than for grasses (3,210 mg kg −1 ). Total plant P concentrations of grasses and legumes increased with soil Mehlich-3 P concentrations in both glasshouse and field trials with concentrations close to 6,000 mg kg −1 in arrowleaf clover at 680 mg kg −1 Mehlich-3 soil P. FRP in water extracts of plant shoots increased relative to plant total P as soil Mehlich-3 P increased, with the greatest concentrations shown by crimson clover and arrowleaf clover. Analysis of water extracts of ryegrass and clover herbage from a field trial showed that while FRP was increasing, phytase-available-P decreased significantly from about 70% of filterable unreactive P at the lowest Mehlich-3 P concentrations, to close to zero at 200 mg kg −1 Mehlich-3 P. The wide variation, and enrichment of FRP in water extracts and total P with increasing Mehlich-3 P among species, indicates that cultivar and site selection and sward management provide a potential option to mitigate P loss to surface waters. Content Type Journal Article Pages 1-13 DOI 10.1007/s11104-010-0687-5 Authors Richard W. McDowell, AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, 9053 New Zealand Andrew N. Sharpley, Department of Soil, Crop and Environmental Science, University of Arkansas, Fayetteville, AR USA James R. Crush, AgResearch, Ruakura Research Centre, Private Bag 3123, Hamilton, 3240 New Zealand Tara Simmons, Department of Soil, Crop and Environmental Science, University of Arkansas, Fayetteville, AR USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Hydraulic redistribution is the process where soil water is translocated by plant roots from wet to dry areas as it is drawn through xylem pathways by a water potential gradient. Hydraulic redistribution places soil water resources where they would otherwise not be, which results in a range of ecological and hydrological consequences. Although deep-rooted plants can transfer water up from depth into shallow soil layers, any localised ‘irrigation’ of neighbouring plants tends to be obscured by recovery of the very same water by the donor plants during daytime transpiration. A new intercropping system was recently trialled which eliminates transpiration by the donor plant through complete shoot removal in order to maximise hydraulic redistribution. In the absence of any transpiring shoots, the donor plants are left to wick water up from depth 24 hours a day via their root systems, to the benefit of neighbouring shallow-rooted crops. This system allows deeper-rooted ‘nurse plants’ to capture water that is out of reach of crops in a ‘water safety-net’ role, which may be of considerable benefit in water-scarce environments. Content Type Journal Article Pages 1-5 DOI 10.1007/s11104-010-0638-1 Authors Stephen S. O. Burgess, School of Plant Biology, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Humidity is an important determinant of the mycotoxin production (DON, ZEA) by Fusarium species in the grain ears. From a landscape perspective humidity is not evenly distributed across fields. The topographically-controlled redistribution of water within a single field rather leads to spatially heterogeneous soil water content and air humidity. Therefore we hypothesized that the spatial distribution of mycotoxins is related to these topographically-controlled factors. To test this hypothesis we studied the mycotoxin concentrations at contrasting topographic relief positions, i.e. hilltops and depressions characterized by soils of different soil moisture regimes, on ten winter wheat fields in 2006 and 2007. Maize was the preceding crop and minimum tillage was practiced in the fields. The different topographic positions were associated with moderate differences in DON and ZEA concentrations in 2006, but with significant differences in 2007, with six times higher median ZEA and two times higher median DON detected at depression sites compared to the hilltops. The depression sites correspond to a higher topographic wetness index as well as redoximorphic properties in soil profiles, which empirically supports our hypothesis at least for years showing wetter conditions in sensitive time windows for Fusarium infections. Content Type Journal Article Pages 1-12 DOI 10.1007/s11104-010-0695-5 Authors Marina Elsa Herta Müller, Leibniz-Centre for Agricultural Landscape Research, Institute of Landscape Matter Dynamics, Eberswalder Str. 84, 15374 Müncheberg, Germany Sylvia Koszinski, Leibniz-Centre for Agricultural Landscape Research, Institute of Soil Landscape Research, Eberswalder Str. 84, 15374 Müncheberg, Germany Alexander Brenning, Department of Geography and Environmental Management, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada Gernot Verch, Leibniz-Centre for Agricultural Landscape Research, Research Station Dedelow, OT Dedelow, Steinfurter Str. 14, 17291 Prenzlau, Germany Ulrike Korn, Leibniz-Centre for Agricultural Landscape Research, Institute of Landscape Matter Dynamics, Eberswalder Str. 84, 15374 Müncheberg, Germany Michael Sommer, Leibniz-Centre for Agricultural Landscape Research, Institute of Soil Landscape Research, Eberswalder Str. 84, 15374 Müncheberg, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Arbuscular mycorrhizal fungi (AMF) are crucial for ecosystem functioning, and thus have potential use for sustainable agriculture. In this study, we investigated the impact of organic and mineral fertilizers on the AMF community composition and content of Glomalin-related soil protein (GRSP) in a field experimental station which was established in 1979, in the Loess Plateau of China. Roots and soils were sampled three times during the growing period of winter wheat in 2008. The treatments including: N (inorganic N), NP (inorganic N and P), SNP (straw, inorganic N and P), M (farmyard manure), MNP (farmyard manure, inorganic N and P), and CK (no fertilization). AMF communities of root and soil samples were analyzed using PCR-DGGE, cloning and sequencing techniques; and GRSP content was determined by Bradford assay. Our results indicated that spore density, GRSP, and AMF community varied significantly in soils of long-term fertilization plots at three different wheat growing stages. The effects of wheat growing period on AMF community in roots were much more evident than fertilization regimes. However, the diversity of AMF was low in our study field. Up to five AMF phylotypes appeared in each sample, with the overwhelming dominance of a Glomus -like phylotype affiliated to G. mosseae . GRSP content was correlated positively with organic carbon, total phosphorus, available phosphorus, soil pH, and spore densities, but correlated negatively with soil C/N ( P  〈 0.05). The results of our study highlight that the richness of AMF in Loess Plateau agricultural region is low, and long-term fertilization, especially amendments with manure and straw, has beneficial effects on accumulation of soil organic carbon, spore density, GRSP content, and AMF diversity. Host phenology, edaphic factors (influenced by long-term fertilization), and habitats interacted to affect the AMF community and agoecosystem functioning. Additionally, soil moisture and pH make a greater contribution than other determined soil parameters to the AMF community dynamics in such a special semi-arid agroecosystem where crops rely greatly on rainfall. Content Type Journal Article Pages 1-15 DOI 10.1007/s11104-010-0688-4 Authors Fasi Wu, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China Maoxing Dong, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China Yongjun Liu, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China Xiaojun Ma, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China Lizhe An, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China J. Peter W. Young, Department of Biology, University of York, PO Box 373, York, YO10 5YW UK Huyuan Feng, School of Life Sciences, Key Lab of Arid and Grassland Ecology of Ministry of Education, Lanzhou University, Lanzhou, 730000 People’s Repulic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Rhizotoxic effects of many trace metals are known, but there is little information on recovery after exposure. Roots of 3-d-old cowpea ( Vigna unguiculata (L.) Walp. cv. Caloona) seedlings were grown for 4 or 12 h in solutions of 960 μM Ca and 5 μM B at two concentrations (which reduce growth by 50 or 85%) of nine trace metals that rupture the outer layers of roots. Measured concentrations were 34 or 160 μM Al, 0.6 or 1.6 μM Cu, 2.2 or 8.5 μM  Ga, 2.3 or 12 μM Gd, 0.8 or 1.9 μM Hg, 1.0 or 26 μM In, 2.4 or 7.3 μM La, 1.8 or 3.8 μM Ru, and 1.3 or 8.6 μM Sc. Roots were rinsed, transferred to solutions free of trace metals, and regrowth monitored for up to 48 h. Recovery from exposure to Hg occurred within 4 h, but regrowth was delayed for ≥ 12 h with Al, Ga, or Ru. There was poor regrowth after 4 or 12 h exposure to Cu, Gd, In, La, or Sc. Roots recovered after being grown for 12 to 48 h in 170 μM Al, 5.1 μM  Ga, 2.0 μM Hg, or 1.4 μM Ru, but the extent of recovery was reduced with longer exposure time. Microscopy showed marked differences in symptoms on roots recovering from exposure to the various trace metals. Differences in (i) concentrations that are toxic, (ii) ability of roots to recover, (iii) time for recovery to occur, and (iv) symptoms that develop, suggest that each trace metal has a unique combination of rhizotoxic effects. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-010-0655-0 Authors F. P. C. Blamey, School of Land, Crop and Food Sciences, The University of Queensland, St. Lucia, Queensland Australia 4072 P. M. Kopittke, School of Land, Crop and Food Sciences, The University of Queensland, St. Lucia, Queensland Australia 4072 J. B. Wehr, School of Land, Crop and Food Sciences, The University of Queensland, St. Lucia, Queensland Australia 4072 N. W. Menzies, School of Land, Crop and Food Sciences, The University of Queensland, St. Lucia, Queensland Australia 4072 Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    We identified the role of various soil parameters and root density as drivers of soil respiration (R s ) in an apple orchard, measured during different periods of the year and at a range of distances from trees, in plots with a different history of nutrient supply. R s was measured in April, May, August and December and studied in relation to soil temperature and moisture, total soil C and N, as well as to fine root density and medium-, and large-sized root density and root N concentration. The study also aimed to partition R s by applying the root regression technique. R s ranged from 0.06 in December to 1.49 g CO 2 m −2  h −1 in August. Average soil temperature alone explained up to 71% of the annual variability of R s , while soil water content was negatively correlated to R s . Fertilization, soil C and N concentration and root N had negligible effects on R s . Fine root density, but not medium- and large-sized root density, contributed to explaining part of the yearly variability of R s and proved to be a good predictor in December, when the statistical significance of the regression made it possible to estimate the autotrophic component of R s as being about 35% of total soil respiration. Content Type Journal Article Pages 1-12 DOI 10.1007/s11104-010-0684-8 Authors Christian Ceccon, Department of Fruit Tree and Woody Plant Sciences, Bologna University, Viale Fanin 46, 40127 Bologna, Italy Pietro Panzacchi, Department of Fruit Tree and Woody Plant Sciences, Bologna University, Viale Fanin 46, 40127 Bologna, Italy Francesca Scandellari, Department of Fruit Tree and Woody Plant Sciences, Bologna University, Viale Fanin 46, 40127 Bologna, Italy Luca Prandi, Department of Fruit Tree and Woody Plant Sciences, Bologna University, Viale Fanin 46, 40127 Bologna, Italy Maurizio Ventura, Department of Fruit Tree and Woody Plant Sciences, Bologna University, Viale Fanin 46, 40127 Bologna, Italy Barbara Russo, Faculty of Computer Science, Free University of Bolzano/Bozen, Piazza Università 1, 39100 Bolzano, Italy Peter Millard, The Macaulay Land Use Research Institute, Aberdeen, AB15 8QJ UK Massimo Tagliavini, Faculty of Science and Technology, Free University of Bolzano/Bozen, Piazza Università 5, 39100 Bolzano, Italy Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Mutations affecting the development of root symbiosis between legume plants ( Fabaceae ) and nodule bacteria (rhizobia) are often associated with pleiotropy. This might either primarily be caused by the mutation or develops as a physiological consequence of a changed nodule structure, number and activity. Three pleiotropic traits were revealed in the pea ( Pisum sativum L.) mutant RisfixC which is of supernodulation/nitrate-tolerant symbiosis (Nts) type. They comprise shortened internodes, reduced shoot dry mass accumulation and increased nitrogen content in the root tissues when compared to the wild type. The changes were expressed in the same degree in asymbiotic and nodulated plants when the effect of symbiotic nitrogen on plant growth was abolished with a saturating nitrate level. Consequently, the pleiotropic traits are inherently associated with the mutation. In RisfixC, the pleiotropy coincided with the presumed absence of the systemic feedback factor regulating nodule number. However, no differences were detected in the comparison of nonnodulating mutant Risnod27 ( sym8 ) with the wild type and of inoculated with noninoculated wild-type plants although these pairs also differ in the presence of the systemic factor. Therefore, the pathway leading from the RisfixC mutant product to pleiotropic changes appears to be independent of systemic nodule number regulation. Implications for the genetic improvement of growth and yield parameters of supernodulating breeding lines are discussed. Content Type Journal Article Pages 1-10 DOI 10.1007/s11104-010-0682-x Authors Karel Novák, Institute of Microbiology AS CR, Vídeňská 1083, 142 20 Prague 4, Czech Republic Ludmila Lisá, Institute of Microbiology AS CR, Vídeňská 1083, 142 20 Prague 4, Czech Republic Vladimír Škrdleta, Institute of Microbiology AS CR, Vídeňská 1083, 142 20 Prague 4, Czech Republic Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    A discrepancy between plant demand and soil supply of nitrogen (N) has been observed in early successional stages of riparian vegetation in interior Alaska. We hypothesized that a hydrologically mediated N supply serves as a mechanism to balance this apparent deficiency of plant N supply. To test this hypothesis, we conducted a tracer experiment and measured the activity of nitrate reductase (NRA) over the summer on the early successional floodplain of the Tanana River in interior Alaska. Isotopic data showed that river-/groundwater was an important source of plant water and that hyporheic N could be absorbed by early successional species. Plant NRA generally increased as the growing season progressed, and NO 3 − -N availability increased. Both Salix interior Rowlee and Populus balsamifera L. used NO 3 − -N, and the timing of plant NRA relative to river discharge chemistry and soil NO 3 − -N concentrations, strongly suggest that plant uptake of NO 3 − -N is coupled to fluvial dynamics. Moreover, this physiological function helps explain the apparent discrepancy between N mineralization and productivity in these riparian ecosystems, and demonstrates that plant N availability in these riparian stands is under significant hydrological control. Content Type Journal Article Pages 1-11 DOI 10.1007/s11104-010-0676-8 Authors Lina Koyama, Graduate School of Informatics, Kyoto University, Kyoto, 606-8501 Japan Knut Kielland, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Phytolith Occluded Carbon (PhytOC) has recently been demonstrated to be an important long-term terrestrial carbon fraction. The aim of this study was to examine the rates of silica accumulation and carbon bio-sequestered within the silica phytoliths of the leaf and stem material of wheat (Triticum sp.) cultivars. The phytolith content of 53 wheat cultivars sourced from 25 countries around the world and grown on a single trial site was first isolated and the PhytOC content then determined. The data shows that the phytolith occluded carbon content of the wheat cultivars ranged from 0.06% to 0.60% of dry leaf and stem biomass: a range of 1,000%. The data also demonstrates that it is the efficiency by which carbon is encapsulated within silica rather than the quantity of silica accumulated by the plant that is the most important factor in determining the relative PhytOC yields. The potential phytolith carbon bio-sequestration rates in the leaf and stem components of these wheat cultivars ranged up to 0.246 t-e-CO 2 ha −1 y −1 . These phytolith carbon bio-sequestration rates indicate a substantial potential (~50 million t-e-CO 2 y −1 ) exists for increasing the rate of secure carbon bio-sequestration in wheat crops using existing cultivars. Content Type Journal Article Pages 1-7 DOI 10.1007/s11104-010-0680-z Authors Jeffrey F. Parr, Southern Cross GeoScience, Southern Cross University, Lismore, NSW 2480, Australia Leigh A. Sullivan, Southern Cross GeoScience, Southern Cross University, Lismore, NSW 2480, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Dynamic root-development models are indispensable for biomechanical and biomass allocation studies, and also play an important role in understanding slope stability. There are few root-development models in the literature, and there is a specific lack of dynamic models. Therefore, the aim of this study is to develop a 3D growth-development model for coarse roots, which is species independent, as long as annual rings are formed. In order to implement this model, the objectives are (I) to interpolate annual growth layers, and (II) to evaluate the interpolations and annual volume computations. The model developed is a combination of 3D laser scans and 2D tree-ring data. A FARO laser ScanArm is used to acquire the coarse-root structure. A MATLAB program then integrates the ring-width measurements into the 3D model. A weighted interpolation algorithm is used to compute cross sections at any point within the model to obtain growth layers. The algorithm considers both the root structure and the ring-width data. The model reconstructed ring profiles with a mean absolute error for mean ring chronologies of 〈9% and for single radii of 〈20%. The interpolation accuracy was dependent on the number of input sections and root curvature. Total volume computations deviated by 3.5–6.6% from the reference model. A new robust root-modelling tool was developed which allows for annual volume computations and sophisticated root-development analyses. Content Type Journal Article Pages 1-18 DOI 10.1007/s11104-011-0797-8 Authors Bettina Wagner, Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland Silvia Santini, Institute for Pervasive Computing, ETH Zurich, 8092 Zurich, Switzerland Hilmar Ingensand, Institute of Geodesy and Photogrammetry, ETH Zurich, 8093 Zurich, Switzerland Holger Gärtner, Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Positive effects of sugar beet (SB) application on soil properties and performance of several woody shrub legumes have been described under heavy metal stress and in diverse degraded environments, especially when combined with arbuscular mycorrhiza (AM). However, information on the combined effect of SB amendments and AM symbiosis in horticultural crop plants under drought stress is scarce. Thus, the main objective of this work was to determine if the combination of treated SB waste and AM fungi results in improved drought tolerance of an horticultural food crop such as lettuce and whether or not the effects observed are linked to enhanced antioxidant activities and regulation of two stress-related genes. Lettuce plants inoculated or not with Glomus intraradices and grown on soil amended or not with a treated SB waste were cultivated under well-watered conditions or subjected to drought stress. Plant growth, expression of two drought responsive genes encoding for Δ 1 -pyrroline-5-carboxylate synthetase and 9-cis -epoxycarotenoid dioxygenase, oxidative damage to lipids and the activity of four antioxidant enzymes were measured. Results showed that the application of treated SB waste resulted negative for the development of AM and nonAM plants (both under well-watered and under drought stress conditions). This effect can not be ascribed to the impairment of specific plant antioxidant defenses. In contrast, a lack of induction of a gene from the ABA biosynthetic pathway was observed in SB-treated plants, which could have contributed to the low performance of these plants. The positive effects of combined application of treated SB waste as amendment and AM fungi have not been shown for a horticultural food crop such as Lactuca sativa . Thus, before starting a program aimed at the utilization of different amendments based on transformed wastes, basic studies on functional and physiological compatibility between the plant and the amendment are necessary. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0805-z Authors Juan Manuel Ruíz-Lozano, Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda nº 1, 18008 Granada, Spain María del Carmen Perálvarez, Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda nº 1, 18008 Granada, Spain Ricardo Aroca, Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda nº 1, 18008 Granada, Spain Rosario Azcón, Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda nº 1, 18008 Granada, Spain Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Urbanization has been rapid across the world but the responses of phosphorus (P) cycling to urbanization have not been well-investigated. This study was to understand the influences of rapid urbanization on forest P cycling in a developing country. Soil P fractions and P resportion were determined for nine slash pine ( Pinus elliottii Engelm.) forests along a 30-km long urban-suburban-rural gradient in Nanchang City, southern China. The total P stocks in the surface soils in urban and suburban forests were 317% and 182% higher, respectively, than levels found in rural forests. The concentrations of soil available P, labile P, slow P, occluded P and total extractable P were also much higher in urban and suburban forests than in rural forests ( P  〈 0.05). Soil weathered P concentrations were highest in urban forests. Annual mean foliar P concentrations were enhanced in urban and suburban forests compared to rural forests. The P resorption efficiency (PRE) was higher in rural forests than in suburban and urban forests, while the P resorption proficiency (PRP) was lower in rural forests than in suburban and urban forests. Urbanization associated with high extraneous P inputs has altered soil P status and plant P uptake. Foliar P concentration, PRE and PRP were largely dependent on soil P availability in our study forests. Content Type Journal Article Pages 1-10 DOI 10.1007/s11104-011-0799-6 Authors Xiao-Fei Hu, College of Life Sciences, Nanchang University, Nanchang, 330031 China Fu-Sheng Chen, College of Life Sciences, Nanchang University, Nanchang, 330031 China Gregory Nagle, Department of Natural Resources, Cornell University, Ithaca, NY 14853, USA Yun-Ting Fang, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650 China Ming-Quan Yu, College of Life Sciences, Jiangxi Science & Technology Normal University, Nanchang, 330038 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Loss of functional diversity has been demonstrated to have a variety of impacts on ecosystem functioning. However, most studies have been implemented in artificially assembled communities by removing the original vegetation and seeding with desired species or functional group compositions. Such approaches could significantly disturb belowground biomass, especially roots, making it difficult to examine belowground responses to diversity manipulations. To circumvent this issue, plant diversity gradients were established by in situ removal of aboveground biomass of different plant functional groups (PFGs) in a typical steppe, and belowground processes related to roots and soil were examined. Root nutrient pools exhibited contrasting patterns, with the phosphorus (P) pool decreasing linearly upon increased PFG removal while the nitrogen (N) pool had a hump-shaped response. Soil NO 3− increased while net N mineralization decreased with PFG removal. In contrast, soil P showed little response to PFG removal. Furthermore, both the identity and number of PFG removed had a significant influence on root and soil properties. The results of this study showed that loss of a combination of PFGs was important in natural grassland, and an approach with minimal influence on belowground processes is promising in studying diversity loss effects in natural ecosystems. Content Type Journal Article Pages 1-12 DOI 10.1007/s11104-011-0803-1 Authors Deliang Kong, Key Laboratory for Urban Habitat Environmental Science and Technology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China Huifang Wu, Department of Horticulture, Institute of Agricultural Sciences, Nanyang, 473000 China Hui Zeng, Key Laboratory for Urban Habitat Environmental Science and Technology, Peking University Shenzhen Graduate School, Shenzhen, 518055 China Xiaotao Lü, Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, 100093 Beijing, China Matthew Simmons, Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, 100093 Beijing, China Meng Wang, Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, 100093 Beijing, China Xiaofang Sun, Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, 100093 Beijing, China Xingguo Han, Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences, No.20 Nanxincun, Xiangshan, 100093 Beijing, China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Cadmium (Cd) toxicity inhibited the seedling growth while inducing the occurrences of lateral roots (LR) and adventitious roots (AR). Further study indicated that auxin and nitric oxide (NO) are involved in the processes. In this study, we chose model plant Arabidopsis thaliana and Cd-hyperaccumulator Solanum nigrum as material to examine the involvement of Cd-induced auxin redistribution in NO accumulation in plants and the effect of NO on Cd accumulation. For this aim, the histochemical staining, NO fluorescence probe (DAF-2DA) detections combined with the pharmacological study were used in this study. By using DR5:GUS staining analysis combined with NO fluorescence probe (DAF-2DA) detection, we found that Cd-induced NO accumulation is at least partly due to auxin redistribution in plants exposure to Cd. Supplementation with SNP donor S-nitrosoglutathione (GSNO) increased the number of LR and AR. In contrast, NO-scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl-3-oxide (cPTIO) reversed the effects of NO on modulating root system architecture and Cd accumulation. These results suggest that manipulation of the NO level is an effective approach to improve Cd tolerance in plants by modulating the development of LR and AR, and provide insights into novel strategies for phytoremediation. Content Type Journal Article Pages 1-13 DOI 10.1007/s11104-011-0800-4 Authors Jin Xu, Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Huaizhong RD 286, Shijiazhuang, 050021 China Wenying Wang, College of Life Science and Geography, Qinghai Normal University, Wusi west RD 38, Xining, 810008 China Jianhang Sun, Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Huaizhong RD 286, Shijiazhuang, 050021 China Yuan Zhang, College of Life Science, Jilin Agricultural University, Changchun, 130118 China Qing Ge, College of Life Science, Gansu Agricultural University, Lanzhou, 730070 China Liguo Du, Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Huaizhong RD 286, Shijiazhuang, 050021 China Hengxia Yin, College of Life Science and Geography, Qinghai Normal University, Wusi west RD 38, Xining, 810008 China Xiaojing Liu, Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Huaizhong RD 286, Shijiazhuang, 050021 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Rhizosphere communities are critical to plant and ecosystem function, yet our understanding of the role of disturbance in structuring these communities is limited. We tested the hypothesis that soil contamination with petroleum hydrocarbons (PHCs) alters spatial patterns of ecto- (ECM) and ericoid (ERM) mycorrhizal fungal and root-associated bacterial community structure in the shared rhizosphere of pine ( Pinus contorta var. latifolia ) and lingonberry ( Vaccinium vitis-idaea ) in reconstructed sub-boreal forest soils. Pine seeds and lingonberry cuttings were planted into containers with an organic (mor humus, FH or coarse woody debris, CWD) layer overlying sandy mineral horizons (Ae and Bf) of forest soils collected from field sites in central British Columbia, Canada. After 4 months, 219 mg cm -2 crude oil was applied to the soil surface of half of the systems; systems were sampled 1 or 16 weeks later. Composition, relative abundance and vertical distribution of pine ECMs were assessed using light microscopy; community profiles were generated using LH-PCR of ribosomal DNA. Multivariate analysis revealed that plant and soil factors were more important determinants of community composition than was crude oil treatment. Fungal communities differed between pine and lingonberry roots; ECM communities were structured by soil layer whereas ERM communities varied between FH and CWD soil systems. Bacterial communities varied between plants and soil layers, indicating properties of ECM and ERM rhizospheres and the soil environment influence bacterial niche differentiation. This integration of mycorrhizal and bacterial community analysis contributes to a greater understanding of forest soil sustainability in forest ecosystems potentially contaminated with PHCs. Content Type Journal Article Pages 1-12 DOI 10.1007/s11104-011-0802-2 Authors Susan J. Robertson, Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9, Canada P. Michael Rutherford, Environmental Science and Engineering, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9, Canada Hugues B. Massicotte, Ecosystem Science and Management, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9, Canada Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    The effects of flooding on rhizospheric organic acid concentrations of three abundant flooding tolerant plant species ( Alternanthera philoxeroides Mart., Arundinella anomala Steud., Salix variegata Franch.) from the water fluctuation zone of the Three Gorges Reservoir (TGR, Yangtze River) were investigated. Soil solution samples of eight low molecular weight organic acids were obtained from rhizotrons using micro suction cups during 3 weeks of waterlogging, after 6 weeks flooding and after a 1 week recovery. To estimate the contribution of water temperature and microbial community, plants in sterile glass bead substrate and original Yangtze sediment were submerged in laboratory at +10°, +20° and +30°C. Waterlogged plants did seldom express a significantly different pattern of rhizospheric organic acid (OA) composition compared to control plants. Flooding caused no burst of organic acid concentration in soil solution: All species express a silencing strategy. Average OA levels were higher in A. anomala rhizosphere than in the other two species, but increased again after resurfacing in all species. Temperature had a stronger influence in sediment than in sterile setup. In contrast to field measurements, succinate, malate and citrate were detected in the sterile setup. Microbial contribution appeared to have great influence on increasing OA occurrence. Content Type Journal Article Pages 1-19 DOI 10.1007/s11104-011-0732-z Authors Christina M. Schreiber, Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Life Sciences, Southwest China University, Chongqing, 400715 People’s Republic of China Bo Zeng, Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Life Sciences, Southwest China University, Chongqing, 400715 People’s Republic of China Vicky M. Temperton, Research Centre Juelich, IBG-2: Plant Sciences, 52425 Juelich, Germany Uwe Rascher, Research Centre Juelich, IBG-2: Plant Sciences, 52425 Juelich, Germany Marian Kazda, Institute of Systematic Botany and Ecology, University Ulm, 89069 Ulm, Germany Ulrich Schurr, Research Centre Juelich, IBG-2: Plant Sciences, 52425 Juelich, Germany Agnes Höltkemeier, Research Centre Juelich, IBG-3: Agrosphere, 52425 Juelich, Germany Arnd J. Kuhn, Research Centre Juelich, IBG-2: Plant Sciences, 52425 Juelich, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    The plasma membrane (PM) H + ATPase is involved in the plant response to nutrient deficiency. However, adaptation of this enzyme in monocotyledon plants to phosphorus (P) deficiency lacks direct evidence. In this study, we detected that P deficient roots of rice ( Oryza Sativa L.) could acidify the rhizosphere. We further isolated the PM from rice roots and analyzed the activity of PM H + ATPase. In vitro, P deficient rice roots showed about 30% higher activity of PM H + ATPase than the P sufficient roots at assay of pH 6.0. The P deficiency resulted in a decrease of the substrate affinity value ( K m ) of PM H + ATPase. The proton pumping activity of membrane vesicles from the P deficient roots was about 70% higher than that from P sufficient roots. Western blotting analysis indicated that higher activity of PM H + ATPase in P deficient roots was related to a slightly increase of PM H + ATPase protein abundance in comparison with that in P sufficient roots. Taken together, our results demonstrate that the P deficiency enhanced activities of both PM H + -ATPase and H + pump, which contributed to the rhizosphere acidification in rice roots. Content Type Journal Article Pages 1-9 DOI 10.1007/s11104-011-0774-2 Authors Ruiping Zhang, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Gan Liu, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Na Wu, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Mian Gu, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Houqing Zeng, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Yiyong Zhu, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Guohua Xu, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    The ancient landscape of the South - West Australian Floristic Region (SWAFR) is characterized by exceptional floristic diversity, attributed to a complex mosaic of nutrient - impoverished soils. Between - soil type differences in nutrient availability are expected to affect floristic assemblage patterns in the SWAFR. We compared patterns of floristic diversity between open - forest samples from three soil types in the high - rainfall zone of the SWAFR. The importance of environmental and spatial factors for species compositional turnover within soil types were evaluated within canonical correspondence analyses using variation partitioning. Patterns of phylogenetic diversity and dispersion were contrasted between soil types and related to differences in soil nutrient availability. Between - quadrat shared phylogenetic branch length for individual life form categories was correlated with explanatory variables using Mantel tests. Species and phylogenetic diversity increased with a decline in soil nutrients and basal area. Nutrient - poorer soils were differentiated by higher species density and phylogenetic diversity, and larger phylogenetic distances between species. Species turnover was best explained by environmental factors when soil nutrient concentrations and basal area were low. Coastal and inland quadrats from the most fertile soil type were distinguished by significantly differing patterns of phylogenetic diversity. Inland quadrats were characterized by strong relationships between phylogenetic diversity and environment, while phylogenetic patterns remained largely unaccounted for by explanatory variables within coastal quadrats. Phylogenetic diversity was more strongly related with environment within upland landform types for nutrient-poor soils. We highlight the complex relationships between climatic and edaphic factors within the SWAFR, and propose that the occurrence of refugial habitat for plant phylogenetic diversity is dynamically linked with these interactions. Climate change susceptibility was estimated to be especially high for inland locations within the high - rainfall zone. Despite the strong relationship between floristic diversity and soil fertility, holistic conservation approaches are required to conserve the mosaic of soil types regardless of soil nutrient status. Content Type Journal Article Pages 1-22 DOI 10.1007/s11104-011-0763-5 Authors Juliane Sander, School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, Queensland, Australia Grant Wardell-Johnson, School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, Queensland, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Root systems are highly plastic as they express a range of responses to acquire patchily distributed nutrients. However, the ecological significance of placing roots selectively in nutrient hotspots is still unclear. Here, we investigate under what conditions selective root placement may be a significant functional trait that determines belowground competitive ability. We studied two grasses differing in root foraging behaviour, Festuca rubra and Anthoxanthum odoratum . The plants were grown in stable and more dynamic heterogeneous environments, by switching nutrient patches halfway through the experiment. A. odoratum was a factor of two less selective in placing its roots into nutrient-rich patches than F. rubra . A. odoratum produced overall higher root length densities with higher specific root length than F. rubra and acquired more nutrients. A. odoratum appeared to be the superior competitor, irrespective of the nutrient dynamics. Our results suggest that root behaviour consisting of producing high root length densities at relatively low biomass investments can be a more effective foraging strategy than placing roots selectively in nutrient hotspots. When understanding the functionality of root traits among different species, specific root length may play a key role. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0752-8 Authors Liesje Mommer, Institute for Water and Wetland Research, Experimental Plant Ecology, Radboud University Nijmegen, P.O. box 9010, 6500 GL, Nijmegen, The Netherlands Eric J. W. Visser, Institute for Water and Wetland Research, Experimental Plant Ecology, Radboud University Nijmegen, P.O. box 9010, 6500 GL, Nijmegen, The Netherlands Jasper van Ruijven, Nature Conservation and Plant Ecology Group, Wageningen UR, P.O. box 47, 6700 AA Wageningen, The Netherlands Hannie de Caluwe, Institute for Water and Wetland Research, Experimental Plant Ecology, Radboud University Nijmegen, P.O. box 9010, 6500 GL, Nijmegen, The Netherlands Ronald Pierik, Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands Hans de Kroon, Institute for Water and Wetland Research, Experimental Plant Ecology, Radboud University Nijmegen, P.O. box 9010, 6500 GL, Nijmegen, The Netherlands Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   The effects of drying and rewetting (DRW) have been studied extensively in non-saline soils, but little is known about the impact of DRW in saline soils. An incubation experiment was conducted to determine the impact of 1–3 drying and re-wetting events on soil microbial activity and community composition at different levels of electrical conductivity in the saturated soil extract (ECe) (ECe 0.7, 9.3, 17.6 dS m −1 ). Methods   A non-saline sandy loam was amended with NaCl to achieve the three EC levels 21 days prior to the first DRW; wheat straw was added 7 days prior to the first DRW. Each DRW event consisted of 1 week drying and 1 week moist (50% of water holding capacity, WHC). After the last DRW, the soils were maintained moist until the end of the incubation period (63 days after addition of the wheat straw). A control was kept moist (50% of WHC) throughout the incubation period. Results   Respiration rates on the day after rewetting were similar after the first and the second DRW, but significantly lower after the third DRW. After the first and second DRW, respiration rates were lower at EC17.6 compared to the lower EC levels, whereas salinity had little effect on respiration rates after the third DRW or at the end of the experiment when respiration rates were low. Compared to the continuously moist treatment, respiration rates were about 50% higher on day 15 (d15) and d29. On d44, respiration rates were about 50% higher at EC9.7 than at the other two EC levels. Cumulative respiration was increased by DRW only in the treatment with one DRW and only at the two lower EC levels. Salinity affected microbial biomass and community composition in the moist soils but not in the DRW treatments. At all EC levels and all sampling dates, the community composition in the continuously moist treatment differed from that in the DRW treatments, but there were no differences among the DRW treatments. Conclusions   Microbes in moderately saline soils may be able to utilise substrates released after multiple DRW events better than microbes in non-saline soil. However, at high EC (EC17.6), the low osmotic potential reduced microbial activity to such an extent that the microbes were not able to utilise substrate released after rewetting of dry soil. Content Type Journal Article Pages 1-11 DOI 10.1007/s11104-011-0918-4 Authors Nasrin Chowdhury, School of Agriculture, Food & Wine, The University of Adelaide, Adelaide, South Australia 5005, Australia Andre S. Nakatani, Universidade de São Paulo, ESALQ, Avenida Pádua Dias, 11, CEP 13418-900, Piracicaba, SP, Brazil Raj Setia, School of Agriculture, Food & Wine, The University of Adelaide, Adelaide, South Australia 5005, Australia Petra Marschner, School of Agriculture, Food & Wine, The University of Adelaide, Adelaide, South Australia 5005, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Erratum to: Prospects and problems of simple linear models for estimating symbiotic N 2 fixation by crop and pasture legumes Content Type Journal Article Pages 1-1 DOI 10.1007/s11104-011-0914-8 Authors M. J. Unkovich, Soil and Land Systems Group, Earth and Environmental Sciences, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia J. Baldock, CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064, Australia M. B. Peoples, CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   We explored drivers of the spatial variability of plant carbon (C) and nitrogen (N) isotopes in the Los Angeles Basin and the implications of such plant isotopes for alterations to urban environments. Methods   We made simultaneous measurements of plant and soil isotopes, air pollutant concentrations, and soil N cycling. The common winter annual Bromus ( B . hordeaceus and B . madritensis ) and 0–10 cm soil were sampled at 13–15 sites located near air quality monitoring stations in 2008 and 2009. Results   The N isotopic composition (δ 15 N) of plants and soils were significantly correlated in both years. The plant-soil δ 15 N enrichment factor (EF), or the deviation of plant δ 15 N from soil δ 15 N, was positively correlated with nitrogen dioxide (NO 2 ) concentrations in 2008 but not in 2009. However, in 2009 plant EF decreased as the relative percentage of net nitrification in the soil (% net nitrification) increased up to 90%. Plant C isotopic composition (δ 13 C) was significantly and negatively correlated with soil moisture and with concentrations of atmospheric carbon monoxide (CO) and NO 2 . Conclusion   Urban plant isotopes may be used as indicators of altered environmental factors such as air pollution and also of soil N cycling. Content Type Journal Article Pages 1-16 DOI 10.1007/s11104-011-0912-x Authors Wenwen Wang, Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697-2525, USA Diane E. Pataki, Department of Earth System Science and Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697-3100, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Excessive accumulation of arsenic (As) in rice ( Oryza sativa L.) may pose a health risk to rice consumers. Long-distance transport of As within plant tissues is not well understood. The aim of our study was to evaluate As translocation from roots to shoots and from shoot tissues to rice grain. Methods   At the grain filling stage, 73 As-labelled arsenite was fed to roots, cut stems or flag leaves of rice. The root-feeding experiment also included a treatment of steam girdling near the base of panicle to block phloem transport. 73 As distribution in different tissues was quantified after 2 or 4 days. Results   In the root-feeding experiment, about 10% of the 73 As taken up was distributed to shoots mostly in stems and leaves, with 3.3% of the shoot 73 As found in the grain. Steam girdling decreased grain 73 As by 97%. In the stem-feeding experiment, most 73 As was retained in the stem with 3.9% distributed to the grain. In the flag leaf-feeding experiment, 12–15% of 73 As was exported to other tissues with 2–3% reaching the grain. Conclusions   As (mainly arsenite) has a relatively low mobility within rice plants. Arsenite was transported to rice grain mainly through the phloem. A small proportion of arsenite fed to flag leaves can be transported to grain. Content Type Journal Article Pages 1-8 DOI 10.1007/s11104-011-0926-4 Authors Fang-Jie Zhao, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK Jacqueline L. Stroud, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK M. Asaduzzaman Khan, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK Steve P. McGrath, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Postfire logging recoups the economic value of timber killed by wildfire, but whether such forest management activity supports or impedes forest recovery in stands differing in structure from historic conditions remains unclear. The aim of this study was to determine the impact of mechanical logging after wildfire on soil bacterial and fungal communities and other measures influencing soil productivity. Methods   We compared soil bacterial and fungal communities and biogeochemical responses of 1) soils compacted, and 2) soils compacted and then subsoiled, to 3) soils receiving no mechanical disturbance, across seven stands, 1–3 years after postfire logging. Results   Compaction decreased plant-available N on average by 27% compared to no mechanical disturbance, while subsoiling decreased plant-available P (Bray) on average by 26% compared to the compacted and non-mechanically disturbed treatments. Neither bacterial nor fungal richness significantly differed among treatments, yet distinct separation by year in both bacterial and fungal community composition corresponded with significant increases in available N and available P between the first and second postharvest year. Conclusions   Results suggest that nutrients critical to soil productivity were reduced by mechanical applications used in timber harvesting, yet soil bacteria and fungi, essential to mediating decomposition and nutrient cycling, appeared resilient to mechanical disturbance. Results of this study contribute to the understanding about impacts of harvesting fire-killed trees and bear consideration along with the recovery potential of a site and the impending risk of future fire in stands with high densities of fire-killed trees. Content Type Journal Article Pages 1-19 DOI 10.1007/s11104-011-0925-5 Authors Tara N. Jennings, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA Jane E. Smith, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 Jefferson Way, Corvallis, OR 97331, USA Kermit Cromack, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA Elizabeth W. Sulzman, Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331, USA Donaraye McKay, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 Jefferson Way, Corvallis, OR 97331, USA Bruce A. Caldwell, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA Sarah I. Beldin, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 Jefferson Way, Corvallis, OR 97331, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Tecticornia species are stem-succulent, perennial halophytes (sub-family Salicornioideae; Chenopodiaceae) that inhabit saline areas including the margins of ephemeral salt lakes in Australia. Based on zonation observed at salt lakes, species were hypothesised to differ in tolerances to salinity and/or waterlogging. Methods   Three Tecticornia species were grown in sub-irrigated or waterlogged sand culture with treatments from 10 to 800 m M NaCl, for 60 d in a glasshouse. Growth, tissue solutes, root porosity, root radial O 2 loss, and ethanol production, were assessed. Results   The three species were salt tolerant; at 800 m M NaCl shoot RGR (ash-free) was reduced by 9% in T. indica , 22% in T. pergranulata and 39% in T. mellaria . Na + and Cl − were the predominant osmotica in succulent stem tissues. Glycinebetaine was a major organic solute. T. pergranulata and T. indica were waterlogging tolerant; shoot RGR was reduced by at most 29% irrespective of salinity. Waterlogging tolerance in T. mellaria was variable (shoot RGR 8%–56% of controls) and some individuals died. T. pergranulata formed adventitious roots with aerenchyma, but the two other species did not. Anoxic tips of lateral roots produced ethanol. Conclusion   The three Tecticornia species are salt tolerant. T. pergranulata is also waterlogging tolerant and formed adventitious roots containing aerenchyma, traits consistent with growth on mud flats of salt lakes. T. indica was unexpectedly tolerant of waterlogging, whereas T. mellaria was less tolerant. Future work is needed to evaluate tolerances of inundation (i.e. submergence) and to higher salinity treatments. Content Type Journal Article Pages 1-18 DOI 10.1007/s11104-011-0924-6 Authors Jeremy P. English, School of Plant Biology (M084), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Timothy D. Colmer, School of Plant Biology (M084), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Introduction   Proper understanding of how rate of OM decomposition varies across a given watershed is important to determine the potential of soil erosion to induce terrestrial carbon (C) sequestration. However, as of yet, our understanding of the spatial variability of rate of organic matter (OM) decomposition ( k ) across a watershed is incomplete, at best. Aim   The objective of this study is to determine how rates of organic substrate decomposition vary on the surface and in soil profiles of eroding vs. depositional landform positions. Methods   To determine rate of organic substrate decomposition in eroding vs. depositional landform positions, a field litterbag decomposition study was conducted in Tennessee Valley, Northern California using in situ foliage (from grasses and a shrub) and two standard substrates (filter paper and birch tongue depressors, that served as proxies for OM that is relatively easier vs. harder to breakdown during microbial decomposition). We conducted the experiment at 3–4 depths at each landform position. Results   The effect of erosional transport (surface to surface transfer of topsoil and associated SOM from eroding to depositional landform positions) and burial (after deposition of eroded SOM by successive erosional events) on decomposition rate of eroded SOM was different depending on the nature of eroding and depositional landform positions considered. The k of organic substrates at 25 cm soil depth in the depositional positions was up to 2 orders of magnitude higher than on the surface of the eroding positions. Results of this litterbag decomposition study suggest that transport of SOM from topsoil of eroding positions to the surface of depositional positions can reduce its k ; but burial of eroded SOM in soil profiles at the depositional positions can lead to increasing k . Conclusion   Because erosion-induced C sequestration is a function of changes in rate of OM decomposition and input post-compared to pre-erosion, our findings suggest that higher rates of plant productivity in eroding watersheds is needed to create and maintain a C sink in such eroding watersheds. Content Type Journal Article Pages 1-20 DOI 10.1007/s11104-011-0902-z Authors Asmeret Asefaw Berhe, School of Natural Sciences, University of California, Merced, 4225 N. Hospital Rd, Castle # 47, Atwater, CA 95301, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   The eutrophication of aquatic systems due to diffuse pollution of agricultural phosphorus (P) is a local, even regional, water quality problem that can be found world-wide. Scope   Sustainable management of P requires prudent tempering of agronomic practices, recognizing that additional steps are often required to reduce the downstream impacts of most production systems. Conclusions   Strategies to mitigate diffuse losses of P must consider chronic (edaphic) and acute, temporary (fertilizer, manure, vegetation) sources. Even then, hydrology can readily convert modest sources into significant loads, including via subsurface pathways. Systemic drivers, particularly P surpluses that result in long-term over-application of P to soils, are the most recalcitrant causes of diffuse P loss. Even in systems where P application is in balance with withdrawal, diffuse pollution can be exacerbated by management systems that promote accumulation of P within the effective layer of effective interaction between soils and runoff water. Indeed, conventional conservation practices aimed at controlling soil erosion must be evaluated in light of their ability to exacerbate dissolved P pollution. Understanding the opportunities and limitations of P management strategies is essential to ensure that water quality expectations are realistic and that our beneficial management practices are both efficient and effective. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0832-9 Authors Peter J. A. Kleinman, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA, USA Andrew N. Sharpley, Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR, USA Richard W. McDowell, AgResearch, Ltd., Invermay Agricultural Centre, Mosgiel, New Zealand Don N. Flaten, Department of Soil Science, University of Manitoba, Winnipeg, Manitoba, Canada Anthony R. Buda, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA, USA Liang Tao, Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources, Beijing, China Lars Bergstrom, Department of Soil Science, Swedish University of Agricultural Sciences, Uppsala, Sweden Qing Zhu, USDA-ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Arbuscular mycorrhizal (AM) fungi contribute to plant nutrient uptake in systems managed with reduced fertilizer and pesticide inputs such as organic agriculture by extending the effective size of the rhizosphere and delivering minerals to the root. Connecting the molecular study of the AM symbiosis with agriculturally- and ecologically-relevant field environments remains a challenge and is a largely unexplored research topic. Methods   This study utilized a cross-disciplinary approach to examine the transcriptional, metabolic, and physiological responses of tomato ( Solanum lycopersicum ) AM roots to a localized patch of nitrogen (N). A wild-type mycorrhizal tomato and a closely-related non-mycorrhizal mutant were grown at an organic farm in soil that contained an active AM extraradical hyphal network and soil microbe community. Results   The majority of genes regulated by upon enrichment of nitrogen were similarly expressed in mycorrhizal and non-mycorrhizal roots, suggesting that the primary response to an enriched N patch is mediated by mycorrhiza-independent root processes. However where inorganic N concentrations in the soil were low, differential regulation of key tomato N transport and assimilation genes indicate a transcriptome shift towards mycorrhiza-mediated N uptake over direct root supplied N. Furthermore, two novel mycorrhizal-specific tomato ammonium transporters were also found to be regulated under low N conditions. A conceptual model is presented integrating the transcriptome response to low N and highlighting the mycorrhizal-specific ammonium transporters. Conclusions   These results enhance our understanding of the role of the AM symbiosis in sensing and response to an enriched N patch, and demonstrate that transcriptome analyses of complex plant-microbe-soil interactions provide a global snapshot of biological processes relevant to soil processes in organic agriculture. Content Type Journal Article Pages 1-18 DOI 10.1007/s11104-011-0890-z Authors Daniel R. Ruzicka, Donald Danforth Plant Science Center, 975 N Warson Rd., St. Louis, MO 63132, USA Natasha T. Hausmann, Department of Land, Air, and Water Resources, University of California, 1 Shields Avenue, Davis, CA 95616, USA Felipe H. Barrios-Masias, Department of Land, Air, and Water Resources, University of California, 1 Shields Avenue, Davis, CA 95616, USA Louise E. Jackson, Department of Land, Air, and Water Resources, University of California, 1 Shields Avenue, Davis, CA 95616, USA Daniel P. Schachtman, Donald Danforth Plant Science Center, 975 N Warson Rd., St. Louis, MO 63132, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   This study aimed to determine whether white lupin adaptation to moderately calcareous soils could be enhanced by lime-tolerant plants and Bradyrhizobium strains. Methods   Fourteen landraces from Italy, Morocco and Egypt and some cultivars were grown in moderate-lime (ML) and low-lime (LL) soil with each of two inoculants, one commercial and one including three Bradyrhizobium strains well-nodulating under ML soil (isolated from other lupin species). Grain yield and above-ground biomass were assessed in large artificial environments that mimicked field conditions. Shoot, root and nodulation traits at onset of flowering were studied in a pot experiment. Results   ML soil severely reduced plant yield, growth and nodulation but increased the harvest index relative to LL. Top-yielding genotypes for grain yield displayed significant rank inversion across soil types (P 〈 0.05). Lime-tolerant genotypes reduced their nodulation in ML soil less than limesusceptible ones. Some landraces outperformed the reference lime-tolerant cultivar Giza 1 in ML soil. One Italian landrace had a lime-tolerant response across agricultural locations. The Moroccan inoculant provided greater nodulation, more shoot residues but similar grain yield in ML soil, and less grain and shoot residues in LL soil, compared with the commercial inoculant. Conclusions   Lupin adaptation to ML soil can be improved mainly through selection of lime-tolerant plants. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0889-5 Authors Paolo Annicchiarico, CRA-Centro di Ricerca per le Produzioni Foraggere e Lattiero-Casearie, viale Piacenza 29, 26900 Lodi, Italy Imane Thami Alami, Institut National de la Recherche Agronomique (INRA), Avenue de la Victoire, BP 415 Rabat, Morocco Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Temperate grassland is one of the major global biome types and is widely used as rangeland. Typically, cold winters are followed by a transition period with soil thawing that may last from days to weeks. Pulse N 2 O emissions during freeze-thaw events have been observed in a range of temperate ecosystem types and may contribute significantly to annual N 2 O emissions. It was shown recently that spring thaw pulse N 2 O emissions dominated annual N 2 O emissions in a steppe region of Inner Mongolia. Even though biogeochemical models are increasingly used for up scaling of N 2 O emissions from terrestrial ecosystems, they still need to be further developed to be capable of both simulating pulse N 2 O emission during spring thaw and accounting for the impact of grazing on soil N 2 O emissions in general. Methods   In this study, we modified an existing biogeochemical model, Mobile-DNDC, to allow an improved simulation of plant production, snow height, and soil moisture for steppe in Inner Mongolia exposed to different grazing intensities. The newly introduced routines relate maximum snow height to end-of-season biomass (ESSB), to account for decreased plant productivity due to grazing and consider the increase of resistance (impedance) of soil ice on the soil hydraulic conductivity. Results   The implementation of the impedance concept, which means the consideration of decreased hydraulic conductivity in frozen soil, resulted in an improved simulation of soil water content and decreased simulated oxygen content in the top soil during freeze-thaw periods. Increased soil moisture and associated oxygen limitation stimulated N 2 O emission by enhanced denitrification. Based on observations in the field, maximum snow height was limited by ESSB, protecting snow against erosion by wind. Since grazing reduced biomass and thereby snow cover, water availability during spring thaw was smaller at grazed sites as compared to ungrazed sites. In agreement with field observations, lower water content and anaerobiosis resulted in decreased N 2 O emissions during spring thaw. Conclusions   The introduction of the impedance concept into Mobile-DNDC is a major step forward in simulating pulse N 2 O emissions from soils during spring-thaw. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0908-6 Authors Benjamin Wolf, Institute for Meteorology and Climate Research (IMK-IFU), Karlsruher Institute of Technology, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany Ralf Kiese, Institute for Meteorology and Climate Research (IMK-IFU), Karlsruher Institute of Technology, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany Weiwei Chen, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute for Atmospheric Physics, Chinese Academy of Sciences (IAP-CAS), 100029 Beijing, China Rüdiger Grote, Institute for Meteorology and Climate Research (IMK-IFU), Karlsruher Institute of Technology, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany Xunhua Zheng, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute for Atmospheric Physics, Chinese Academy of Sciences (IAP-CAS), 100029 Beijing, China Klaus Butterbach-Bahl, Institute for Meteorology and Climate Research (IMK-IFU), Karlsruher Institute of Technology, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   This study investigated initial land-use change effects on ecosystem biomass, carbon (C) and nitrogen (N) allocation and storage by comparing a recently afforested grassland with an adjacent intensively managed grassland in southern Ireland. Methods   Soil C, N and fine root (〈2 mm) stocks were determined from soil cores. Above ground biomass, C and N stocks were estimated from biomass clipping, inventory and allometric biomass equations developed for ash ( Fraxinus excelsior L.) and black alder ( Alnus glutinosa L.) in the 5-year-old forest plantation. Results   Five years after grassland afforestation, the mean fine root stock of 0.31 kg m −2 in the forest was about half that of 0.64 kg m −2 in the grassland. This decrease was offset by an additional gain of 0.36 kg m −2 in tree biomass since afforestation. The above- to below ground biomass ratio shifted from 0.20 in the grassland to 1.59 in the forest. From May to October, mean net N mineralization was significantly lower in the forest compared to the grassland. Soil C and N concentrations in the 0–10 cm soil layer were significantly higher in the forest (62 mg C g −1 ; 5.7 mg N g −1 ) compared to the grassland (45 mg C g −1 ; 3.6 mg N g −1 ). However, the bulk density in the upper forest soil layer was lower than in the grassland. As a result, no differences existed between the respective total (0–30 cm depth) soil C and N stocks. Total ecosystem C and N storage was also similar for the forest (9.5 kg C m −2 ; 0.75 kg N m −2 ) and the grassland (9.3 kg C m −2 ; 0.77 kg N m −2 ). Conclusions   A significant change in total ecosystem C and N following afforestation of this intensively managed grassland was not observed. Nevertheless, this study highlights immediate implications from such land-use change activities on biomass, C and N reallocation among the above- and belowground ecosystem pools which may subsequently affect ecosystem biogeochemical cycles. Content Type Journal Article Pages 1-16 DOI 10.1007/s11104-011-0905-9 Authors Matthias Peichl, Center for Hydrology, Micrometeorology & Climate Change, Department of Civil and Environmental Engineering, University College Cork, Cork, Republic of Ireland Natalie Anne Leava, Center for Hydrology, Micrometeorology & Climate Change, Department of Civil and Environmental Engineering, University College Cork, Cork, Republic of Ireland Gerard Kiely, Center for Hydrology, Micrometeorology & Climate Change, Department of Civil and Environmental Engineering, University College Cork, Cork, Republic of Ireland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   A key issue related to the usefulness of the minirhizotron technique is whether root presence and behaviour in the soil zone at the minirhizotron interface are consistent with those in the bulk soil. We wanted to test the null hypotheses that there were no differences in root densities or specific root length (SRL) between those positions. The effects of different nutrient and water regimes, and different tree species (grey alder and basket willow) on the root variables were also examined. Methods   We quantified root mass and length densities, and calculated SRL, of three diameter classes from cores sampled around minirhizotrons and in the bulk soil, i.e. quartz sand. Fine root dynamics were monitored in the minirhizotrons during three consecutive years prior to sampling. The study was conducted on individual root systems within buried and covered lysimeters, placed in a stand structure, and with different water and nutrient regimes. Results   Significant discrepancies in root densities were found between positions. Plants subjected to limited water or nutrient supply had up to three times higher densities at the minirhizotrons. However, effects of species and treatments showed a similar pattern for the diameter class 〈1 mm between the two sampling positions and minirhizotron observations. The pulses of fine root growth and decay were coordinated in time for both species and treatments. The SRL was not affected by the tube in any diameter class. Conclusions   We concluded that the minirhizotron technique alone was of limited use for estimating root densities in the bulk soil. But the results showed that minirhizotrons could be useful, for example, combined with soil coring or in comparative studies. The patterns of fine root growth and decay were similar for species and treatments, and SRL was unaffected, suggesting that minirhizotrons can be used in studies of root dynamics and morphology. There is, however, a need for further studies concerning the influence on root survival and decay. Content Type Journal Article Pages 1-16 DOI 10.1007/s11104-011-0896-6 Authors Rose-Marie Rytter, Rytter Science, Backavägen 16, SE-26868 Röstånga, Sweden Lars Rytter, Rytter Science, Backavägen 16, SE-26868 Röstånga, Sweden Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims:   The idea of immobilizing Fe and the formation of a slow-release fertilizer has been considered in several studies. However, none of the proposed materials were found efficient in correcting Fe deficiency. In the present study immobilization of Fe chelates on a solid matrix, as a first step in the production and supply process, is tested. Methods:   The free forms of the siderophores desferrioxamine B (DFOB) and ethylendiaminebis( o -hydroxyphenyl-acetic acid) (EDDHA) were immobilized on p -nitrophenylchloroformate activated Sepharose and tested as Fe source for both strategy I (peanuts and cucumber, Arachis hypogeae L. and Cucumis sativus L., respectively) and strategy II (barley and wheat, Hordeum vulgare L. and Triticum aestivum L., respectively), plants. Plants grown in hydroponic cultures at pH 7.3 were supplied with the immobilized Fe-chelate either free in solution or confined in a dialysis tube with or without EDDHA in the outer solution as a carrier. Results:   Cucumber and barley plants were found efficient in acquiring Fe from the immobilized chelates. Conclusions:   The effectiveness in utilizing the immobilized Fe-chelate differed among cultivars and was related to the efficiency of the reductases activity or phytosiderophores secretion systems, in Strategy I and Strategy II plants, respectively. Content Type Journal Article Pages 1-13 DOI 10.1007/s11104-011-0923-7 Authors Zehava Yehuda, Department of Soil and Water Sciences, Robert H. Smith Faculty of Agriculture Food and Environment, The Hebrew University of Jerusalem, P.O.B. 12, Rehovot, 76100 Israel Yitzhak Hadar, Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture Food and Environment, The Hebrew University of Jerusalem, P.O.B. 12, Rehovot, 76100 Israel Yona Chen, Department of Soil and Water Sciences, Robert H. Smith Faculty of Agriculture Food and Environment, The Hebrew University of Jerusalem, P.O.B. 12, Rehovot, 76100 Israel Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Biochar’s role as a carbon sequestration agent, while simultaneously providing soil fertility improvements when used as an amendment, has been receiving significant attention across all sectors of society, ranging from academia, industry, government, as well as the general public. This has lead to some exaggeration and possible confusion regarding biochar’s actual effectiveness as a soil amendment. One sparsely explored area where biochar appears to have real potential for significant impact is the soil nitrogen cycle. Scope   Taghizadeh-Toosi et al. (this issue) examined ammonia sorption on biochar as a means of providing a nitrogen-enriched soil amendment. The longevity of the trapped ammonia was particularly remarkable; it was sequestered in a stable form for at least 12 days under laboratory air flow. Furthermore, the authors observed increased 15 N uptake by plants grown in soil amended with the 15 N-enriched biochar, indicating that the 15 N was not irreversibly bound, but, was plant-available. Conclusions   Their observations add credence to utilizing biochar as a carrier for nitrogen fertilization, while potentially reducing the undesired environmental consequences through gas emissions, overland flow, and leaching. Content Type Journal Article Pages 1-8 DOI 10.1007/s11104-011-0930-8 Authors Kurt A. Spokas, USDA-ARS, Soil and Water Management Unit, 1991 Upper Buford Circle – 439 Borlaug Hall, St. Paul, MN 55108, USA Jeff M. Novak, USDA-ARS, Coastal Plains Soil, Water, and Plant Research Center, 2611 W. Lucas Street, Florence, SC 29501, USA Rodney T. Venterea, USDA-ARS, Soil and Water Management Unit, 1991 Upper Buford Circle – 439 Borlaug Hall, St. Paul, MN 55108, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   To study the relationship between changes in soil properties and plant community characters produced by grazing in a meadow steppe grassland and the composition and diversity of spore-producing arbuscular mycorrhizal fungi (AMF). Methods   A field survey was carried out in a meadow steppe area with a gradient of grazing pressures (a site with four grazing intensities and a reserve closed to grazing). The AMF community composition (characterized by spore abundance) and diversity, the vegetation characters and soil properties were measured, and root colonization by AMF was assessed. Results   AMF diversity (richness and evenness) was higher under light to moderate grazing pressure and declined under intense grazing pressures. Results of multiple regressions indicated that soil electrical conductivity was highly associated with AMF diversity. The variation in AMF diversity was partially associated to the density of tillers of the dominant grass ( Leymus chinensis ), the above and below-ground biomass and the richness of the plant community. Conclusions   We propose that the relationship between plants and AMF is altered by environmental stress (salinity) which is in turn influenced by animal grazing. Direct and indirect interactions between vegetation, soil properties, and AMF community need to be elucidated to improve our ability to manage these communities. Content Type Journal Article Category Regular Article Pages 1-14 DOI 10.1007/s11104-011-0985-6 Authors Lei Ba, Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, 130024 People’s Republic of China Jiaxu Ning, Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, 130024 People’s Republic of China Deli Wang, Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, 130024 People’s Republic of China Evelina Facelli, School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, Australia José M. Facelli, School of Earth and Environmental Science, The University of Adelaide, Adelaide, SA, Australia Yaning Yang, Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, 130024 People’s Republic of China Lichao Zhang, Institute of Grassland Science, Northeast Normal University, Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, 130024 People’s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   In line with the Stress Gradient Hypothesis, studies of facilitation have tended to focus on plant–plant interactions (biotic nurses), while the relative role of abiotic nurses has been little studied. We assessed the role of biotic and abiotic nurses, and their interaction, on soil enhancement and the consequential performance of a native annual grass, Dactyloctenium radulans . Methods   We used a growth chamber study with two levels of water application to compare the performance of D. radulans growing in soil from foraging pits of the Short-beaked echidna ( Tachyglossus aculeatus ; abiotic nurse) and non-pit soil from either under tree canopies (biotic nurse) or surrounding open areas. Results   All measures of plant performance were more pronounced under the high than the low water treatment. The greatest differences between pit and surface Microsites occurred under the low water application, reinforcing our view that facilitatory effects are greater in resource-limited environments. Despite tree canopy soil having greater N, there was no significant effect on plant performance, nor any significant interaction with Microsite. Conclusions   Our study provides strong evidence that foraging pits enhance soil properties and this soil, in turn, facilitates plant growth; and supports previous work documenting the positive effect of nurse-protégé interactions under greater levels of abiotic stress. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-011-1000-y Authors Samantha K. Travers, Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia David J. Eldridge, Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia Terry B. Koen, Office of Environment and Heritage, P.O. Box 445, Cowra, NSW 2794, Australia Santiago Soliveres, Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Soils derived from serpentinite (serpentine soils) often have low macronutrient concentrations, exceedingly low Ca:Mg molar ratios and high heavy metal concentrations, typically resulting in sparse vegetative cover. This combined suite of edaphic stresses is referred to as the “serpentine syndrome.” Although several plant community-level studies have been conducted to identify the most important edaphic factor limiting plant growth on serpentine, the primary factor identified has often varied by plant community and local climate. Few studies to date have been conducted in serpentine plant communities of alpine or boreal climates. The goal of our study was to determine the primary limiting edaphic factors on plant community species composition and productivity (cover) in the alpine and boreal climate of the Western Alps, Italy. Methods   Soil properties and vegetation composition were analyzed for several sites underlain by serpentinite, gabbro, and calc-schist substrates and correlated using direct and indirect statistical methods. Results   Boreal forest soils were well-developed and tended to have low pH throughout the soil profile resulting in high Ni availability. Alpine soils, in comparison, were less developed. The distinct serpentine plant communities of the Western Alps are most strongly correlated with high levels of bioavailable Ni associated with low soil pH. Other factors such as macronutrient deficiency, low Ca:Mg molar ratio and drought appear to be less important. Conclusions   The strong ecological influence of Ni is caused by environmental conditions which increase metal mobilization. Content Type Journal Article Category Regular Article Pages 1-23 DOI 10.1007/s11104-011-0932-6 Authors Michele E. D’Amico, Department of Environmental Sciences, University of Milano Bicocca, Piazza della Scienza 1, 20126 Milan, Italy Franco Previtali, Department of Environmental Sciences, University of Milano Bicocca, Piazza della Scienza 1, 20126 Milan, Italy Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The aim of the present study was to compare lead accumulation and tolerance among heavy metal hyperaccumulating and non-hyperaccumulating metallophytes. Methods   To this purpose, we compared Pb tolerance and accumulation in hydroponics among calamine and non-calamine populations of Silene vulgaris , Noccaea caerulescens , and Matthiola flavida . We established the effects of Ca on Pb tolerance and accumulation in M. flavida , and measured exchangeable soil Pb and Ca at two calamine sites. Results   Results revealed that calamine populations of S. vulgaris and N. caerulescens were Pb hypertolerant, but the calamine M. flavida population was not. Pb hyperaccumulation capacity was exclusively found in one of the calamine N. caerulescens populations. Conclusions   1) Pb hypertolerance is sometimes lacking in metallophyte populations from strongly Pb-enriched soil, probably due to a relatively high level of exchangeable soil Ca, 2) Ca effectively counteracts Pb uptake and Pb toxicity, 3) The tendency to hyperaccumulate Pb is a population-specific phenomenon in N. caerulescens , 4) Pb hypertolerance in N. caerulescens is not necessarily associated with a tendency to hyperaccumulate Pb, 5) apparent natural Pb hyperaccumulation in M. flavida is not reproducible in hydroponics, probably due to the absence of air-born contamination in laboratory experiments. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1007/s11104-011-0994-5 Authors Ahmad Mohtadi, Department of Biology, University of Isfahan, Isfahan, 81746-73441 Iran Seyed Majid Ghaderian, Department of Biology, University of Isfahan, Isfahan, 81746-73441 Iran Henk Schat, Department of Genetics, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims and methods   Concentrations of heavy metals such as Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in different tissues (seeds, roots and shoots) of the mature canola ( Brassica napus L. ) plants and in the associated rhizosphere soils from Yangtze River Delta (YRD) region of China, were determined to evaluate the heavy metals’ pollution in the soils and the canola seeds, and to discuss their accumulation and translocation characteristics in canola plants. At the same time, the phytoextraction potential of the canola plant for the above heavy metals was theoretically calculated and discussed on the basis of above measured data. Results   The results showed that the concentration ranges of Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in the rhizosphere soils were 0.115–0.481, 3.40–20.5, 0.069–0.682, 9.92–27.4, 46.8–86.6, 17.7–253.3, 65.2–511.7 and 16.0–37.8 mg kg −1 , respectively. The concentrations of Cu, Zn and Hg at some sampling sites exceeded the 2nd grade threshods of Chinese national environmental quality standard for soils. The potential ecological risk of heavy metals in the canola rhizosphere soils decreased in the order of Zhejiang 〉 Shanghai 〉 Jiangsu provinces. The concentration ranges of above heavy metals in the canola seeds were 0.032–0.067, 0.002–0.005, 0.001–0.005, 0.053–0.165, 0.191–0.855, 3.01–13.20, 34.82–96.95 and 0.343–2.86 mg kg −1 , respectively, with Cu and Zn at some sampling sites exceeding the permissible concentrations in foods of China. Heavy metals’ concentrations in canola seeds didn’t increase with their increasing concentrations in the rhizosphere soils. The bioconcentration factors (BCFs) of most heavy metals in the canola seeds decreased with their increasing concentrations in the associated rhizosphere soils. The average BCFs of heavy metals decreased in the order of Zn (0.488)〉Cd (0.241)〉Cu (0.145)〉Ni (0.038)〉Hg (0.021)〉Pb (0.005)=Cr (0.005)〉As (0.000) in the canola seeds, Cd (1.550)〉Cu (0.595)〉Zn (0.422)〉Hg (0.138)〉Ni (0.085)〉Pb (0.080)〉As (0.035)〉Cr (0.031) in the roots, and Cd (0.846)〉Zn (0.242)〉Cu (0.205)〉Hg (0.159)〉Ni (0.031)〉Pb (0.025)〉As (0.012)〉Cr (0.007) in the shoots, respectively. The accumulation capacity for most of the above heavy metals in the mature canola tissues was root 〉 shoot 〉 seed, with the exceptions of seed 〉 root 〉 shoot for Zn and shoot 〉 root 〉 seed for Hg. Except Hg from root to shoot and Zn from root to seed, translocation factors (TFs) of above heavy metals were lower than 1.0. Conclusions   The concentrations, BCFs and TFs of above heavy metals in the canola tissues indicated that the investigated canola plants did not meet the criteria of hyperaccumulators for the above heavy metals. The phytoextracton potential of the studied canola plants for the above heavy metals from the polluted soils was very limited. It would take 920, 3,170 and 3,762 years (assuming two crops per year) to reduce the initial soil Zn, Cu and Hg concentrations, respectively, from the most polluted soil concentrations to the 2nd grade thresholds of Chinese national environmental quality standard for soils. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-1006-5 Authors Ruilian Yu, Institute of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093 China Junfeng Ji, Institute of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093 China Xuyin Yuan, College of Environment, Hohai University, Nanjing, 210098 China Yinxian Song, Institute of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093 China Cheng Wang, Institute of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates. Methods   A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the 15 N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada. Results   Gross N mineralization and gross NH 4 + immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg -1 soil d -1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) and cumulative N 2 O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N 2 O emission was lower at 65% WHC. Conclusions   The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N 2 O emissions in both soils. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-0997-2 Authors Yi Cheng, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Zu-cong Cai, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Jin-bo Zhang, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Man Lang, College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044 China Bruno Mary, INRA, Unit Agro-Impact, Site de Laon, Pole du Griffon, 02000 Barenton-Bugny, France Scott X. Chang, Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, T6G 2E3 Canada Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Belowground DNA-based techniques: untangling the network of plant root interactions Content Type Journal Article Category Commentary Pages 1-7 DOI 10.1007/s11104-011-0962-0 Authors Liesje Mommer, Nature Conservation and Plant Ecology, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands Alex J. Dumbrell, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ UK C. (Niels) A. M. Wagemaker, Molecular Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands N. Joop Ouborg, Molecular Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Iron (Fe) is an essential micronutrient, and plant available Fe is often limited in alkaline soils. Fe deficiency chlorosis decreases plant growth and yield. Identification of germplasm with high and low Fe use efficiency will allow studies to better understand the genetic components for breeding Fe efficient varieties. Methods   A screen using cucumber ( Cucumis sativus ) seedlings identified varieties that maintained contrasting levels of chlorophyll under Fe deficiency or limitation. A time course of mineral dynamics in cotyledons was conducted. Results   The variety Ashley had the highest chlorophyll under Fe deficiency and per unit Fe in the leaf, while the variety Miniature White had the lowest. Ashley also maintained higher chlorophyll when challenged with low Fe or bicarbonate, accumulated greater quantities of Fe, and had higher root ferric reductase activity. Cotyledons accumulated minerals for the first several days, then Fe, P, K, and Cu were remobilized. The Fe use efficient and inefficient varieties remobilized Fe and P on different timescales. Conclusions   Our results suggest that this screen can identify varieties for systems level studies that could elucidate factors needed for Fe use efficiency and remobilization of minerals. The time course indicated that cotyledon Fe stores did not contribute to seedling Fe use efficiency. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-0988-3 Authors Brian M. Waters, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68583-0915, USA Grace C. Troupe, Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68583-0915, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Most cereals accumulate Si in their shoots. Soil bioavailability of Si may be a constraint on the beneficial role of silica in cereals but it is not yet well supported by field data. The aim of this study is to evaluate the long-term impact of wheat straw exports on the pool of soil phytoliths, which, it is suggested, represents the most labile and renewable pool of soil Si. Methods   We measured the amorphous Si (ASi) in soils from several experiments at Rothamsted Research (UK), which provided long-term soil data back to the middle of the 19th century, using two alternative extraction techniques: Na 2 CO 3 (referred to as AS nc ) or zinc bromide extraction (referred to as ASi zb ). Results   All samples showed a similar range of AS nc and ASi zb but low values (0.1–3.4 mg g −1 DW) compared to published data on natural ecosystems. In the Broadbalk experiment, a decrease over time in ASi in the topsoil samples is in good agreement with the hypothesis that cropping and exports of straw leads to depletion of soil phytoliths. A decrease in Si concentration in straw samples was observed between 1883 and 1944. From 1944 to the present, Si concentration increased irregularly in the straw, probably as the result of liming, which enhanced the dissolution of the remaining phytoliths through increasing pH. In the reforested Geescroft field the higher phytolith concentration in the modern topsoil samples is in good agreement with a re-building of phytolith storage from litter input in an acidic environment. Conclusions   Our results therefore support the hypothesis that export of wheat straw leads to a decrease in bioavailable Si. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-0987-4 Authors Flore Guntzer, CEREGE CNRS/Aix-Marseille Université, Europôle Méditerranéen de l′Arbois, 13545 Aix-en-Provence, cedex 4, France Catherine Keller, CEREGE CNRS/Aix-Marseille Université, Europôle Méditerranéen de l′Arbois, 13545 Aix-en-Provence, cedex 4, France Paul R. Poulton, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK Steve P. McGrath, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK Jean-Dominique Meunier, CEREGE CNRS/Aix-Marseille Université, Europôle Méditerranéen de l′Arbois, 13545 Aix-en-Provence, cedex 4, France Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Characterisation of genetic variation in nitrate accumulation by lettuce will inform strategies for selecting low-nitrate varieties more capable of meeting EU legislation on harvested produce. This study uses a population of recombinant inbred lines (RILs) of lettuce to determine how genotypic differences influence N uptake, N assimilation and iso-osmotic regulation, and to identify key related traits prior to future genetic analysis. Methods   Measurements were made on plants grown to maturity in soil fertilised with ammonium nitrate, and in a complete nutrient solution containing only nitrate-N. A simple osmotic balance model was developed to estimate variations in shoot osmotic concentration between RILs. Results   There were significant genotypic variations in nitrate accumulation when plants were grown either with nitrate alone or in combination with ammonium. Ammonium-N significantly reduced nitrate in the shoot but had no effect on its relative variability, or on the ranking of genotypes. Shoot nitrate-N was correlated positively with total-N and tissue water, and negatively with assimilated-C in both experiments. Corresponding relationships with assimilated-N and shoot weight were weaker. Estimated concentrations of total osmotica in shoot sap were statistically identical in all RILs, despite variations in nitrate concentration across the population. Conclusions   Approximately 73% of the genotypic variability in nitrate accumulation within the population of RILs arose from differences in nitrate uptake and only 27% from differences in nitrate assimilated, irrespective of whether or not part of the N was recovered as ammonium, or whether the plants were grown in soil or solution culture. Genotypic variability in nitrate accumulation was associated with changes in concentrations of other endogenous solutes (especially carboxylates and soluble carbohydrates) and of tissue water, which minimised differences in osmotic potential of shoot sap between RILs. This offers the opportunity of using the regulation of these solutes as additional traits to manipulate nitrate accumulation. Content Type Journal Article Category Regular Article Pages 1-19 DOI 10.1007/s11104-011-0999-0 Authors Ian G. Burns, Warwick Crop Centre, School of Life Sciences, Wellesbourne Campus, University of Warwick, Wellesbourne, Warwick, CV35 9EF UK James Durnford, Warwick Crop Centre, School of Life Sciences, Wellesbourne Campus, University of Warwick, Wellesbourne, Warwick, CV35 9EF UK James Lynn, Applied Statistical Solutions, 10 Church Hill, Bishops Tachbrook, Warwickshire, CV33 9RJ UK Sandy McClement, Warwick Crop Centre, School of Life Sciences, Wellesbourne Campus, University of Warwick, Wellesbourne, Warwick, CV35 9EF UK Paul Hand, Harper Adams University College, Newport, Shropshire TF10 8NB, UK David Pink, Harper Adams University College, Newport, Shropshire TF10 8NB, UK Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Many plant-beneficial microorganisms can influence secondary plant metabolism, but whether these effects add up when plants are co-inoculated is unclear. This issue was assessed, under field conditions, by comparing the early impacts of seed inoculation on secondary metabolite profiles of maize at current or reduced mineral fertilization levels. Methods   Maize seeds were inoculated singly with selected strains from bacterial genera Pseudomonas and Azospirillum or mycorrhizal genus Glomus , or with these strains combined two by two or all three together. At 16 days, maize root methanolic extracts were analyzed by RP-HPLC and secondary metabolites (phenolics, flavonoids, xanthones, benzoxazionoids, etc.) identified by LC/MS. Results   Inoculation did not impact on plant biomass but resulted in enhanced total root surface, total root volume and/or root number in certain inoculated treatments, at reduced fertilization. Inoculation led to qualitative and quantitative modifications of root secondary metabolites, particularly benzoxazinoids and diethylphthalate. These modifications depended on fertilization level and microorganism(s) inoculated. The three selected strains gave distinct results when used alone, but unexpectedly all microbial consortia gave somewhat similar results. Conclusions   The early effects on maize secondary metabolism were not additive, as combining strains gave effects similar to those of Glomus alone. This is the first study demonstrating and analyzing inoculation effects on crop secondary metabolites in the field. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-011-0960-2 Authors Vincent Walker, Université de Lyon, 69622 Lyon, France Olivier Couillerot, Université de Lyon, 69622 Lyon, France Andreas Von Felten, Institute of Integrative Biology, ETH, CH-8092 Zürich, Switzerland Floriant Bellvert, Université de Lyon, 69622 Lyon, France Jan Jansa, Institute of Plant Agricultural Sciences, ETH, Eschikon 33, CH-8315 Lindau, Switzerland Monika Maurhofer, Institute of Integrative Biology, ETH, CH-8092 Zürich, Switzerland René Bally, Université de Lyon, 69622 Lyon, France Yvan Moënne-Loccoz, Université de Lyon, 69622 Lyon, France Gilles Comte, Université de Lyon, 69622 Lyon, France Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Soil-plant-microbe interactions from microscopy to field practice Content Type Journal Article Category Editorial Pages 1-5 DOI 10.1007/s11104-011-0969-6 Authors Lynette K. Abbott, School of Earth and Environment, The UWA institute of Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia Caixian Tang, Department of Agriculture Science/Centre for AgriBioscience, La Trobe University, Melbourne Campus, Bundoora, VIC 3086, Australia Doug Reuter, Reuter and Associates, Medindie, SA 5081, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Higher plants are an understudied component of the global silicon cycle; they absorb silicic acid (dSi) which is stored as biogenic silica (bSiO 2 ). Si is believed to alleviate physical, chemical, and biological stresses such as storms, high salinity, heavy metal toxicity, grazing, and disease. We investigated a Si-accumulating invasive species growing in the tidal marshes of the Bay of Brest (France), viz., Spartina alterniflora . Our objectives were to determine (1) where and when bSiO 2 accumulates in the plant during its life cycle, (2) whether this accumulation varies with abiotic factors: wave action, estuarine salinity, and duration of immersion, and (3) if the accumulation was limited by dSi availability in marsh porewater. Methods   A 2 years field survey permitted to sample plants which were analyzed for there bSiO 2 concentrations. Sediment cores were sampled seasonally and the dSi concentrations in the porewater were measured from 0 to 10 cm. Results   bSiO 2 accumulated more in mature leaves than in other organs. There was a strong linear relationship between bSiO 2 concentration and plant length. bSiO 2 concentrations did not increase, but rather decreased as a function of exposure to the three abiotic factors tested. dSi availability was not significantly different for each of the tested sites and dSi profiles did not exhibit huge losses in the root zone. Conclusions   Our evidence suggests that dSi availability did not seem to be a limiting factor. bSiO 2 did not increase with increasing abiotic stresses but was strongly correlated with growth. Hence, S. alterniflora is likely to have other adaptive strategies for dealing with environmental stressors but it did not exclude the possible role of Si in alleviating these stresses. If this is the case, there remain intriguing questions about Si uptake, its availability, and its role in silicification and growth. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-011-0986-5 Authors Jérémy Querné, LEMAR UMR6539, U.B.O, Institut Universitaire Européen de la Mer, I.U.E.M, Université de Bretagne Occidentale, place Nicolas Copernic, 29280 Plouzane, France Olivier Ragueneau, LEMAR UMR6539, U.B.O, Institut Universitaire Européen de la Mer, I.U.E.M, Université de Bretagne Occidentale, place Nicolas Copernic, 29280 Plouzane, France Nathalie Poupart, LEBHAM EA3877, U.B.O, Institut Universitaire Européen de la Mer, I.U.E.M, Université de Bretagne Occidentale, place Nicolas Copernic, 29280 Plouzane, France Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Biochar has been shown to aid soil fertility and crop production in some circumstances. We investigated effects of the addition of Jarrah ( Eucalyptus marginata ) biochar to a coarse textured soil on soil carbon and nitrogen dynamics. Methods   Wheat was grown for 10 weeks, in soil treated with biochar (0, 5, or 25 t ha −1 ) in full factorial combination with nitrogen (N) treatments (organic N, inorganic N, or control). Samples were analysed for plant biomass, soil microbial biomass carbon (MBC) and nitrogen (MBN), N mineralisation, CO 2 evolution, community level physiological profiles (CLPP) and ammonia oxidising bacterial community structure. Results   MBC significantly decreased with biochar addition while MBN was unaltered. Net N mineralisation was highest in control soil and significantly decreased with increasing addition of biochar. These findings could not be attributed to sorption of inorganic N to biochar. CO 2 evolution decreased with 5 t ha −1 biochar but not 25 t ha −1 . Biochar addition at 25 t ha −1 changed the CLPP, while the ammonia oxidising bacterial community structure changed only when biochar was added with a N source. Conclusion   We conclude that the activity of the microbial community decreased in the presence of biochar, through decreased soil organic matter decomposition and N mineralisation which may have been caused by the decreased MBC. Content Type Journal Article Category Regular Article Pages 1-14 DOI 10.1007/s11104-011-1067-5 Authors D. N. Dempster, Soil Biology Group, School of Earth and Environment, UWA Institute of Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia D. B. Gleeson, Soil Biology Group, School of Earth and Environment, UWA Institute of Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Z. M. Solaiman, Soil Biology Group, School of Earth and Environment, UWA Institute of Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia D. L. Jones, School of the Environment, Natural Resources and Geography, Environment Centre Wales, Bangor University, Gwynedd, LL57 2UW UK D. V. Murphy, Soil Biology Group, School of Earth and Environment, UWA Institute of Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Phosphorus (P) deficiency is wide-spread in agricultural soils. In light of increasing P fertilizer costs, it is of interest to assess the capacity of soil microbes to mobilise native soil P and added P. There is currently no method to assess P mobilisation in situ. Methods   The soil P mobilisation potential was assessed by incubating low P soil for up to 30 days with poorly available P sources; C and N were added to increase microbial activity and ensure that only P was limiting microbial growth. Results   The increase in microbial P from day 0 to day 15 showed that microbes were able to mobilise P from FePO 4 and phytate. The P mobilisation potential (sum of microbial and resin P) of the rhizosphere soil decreased in the following order: faba bean 〉 chickpea and white lupin 〉 wheat. After 10 days, up to 80% of the mobilised P was microbial P, whereas after 30 days, almost all P mobilised was resin P. Conclusions   The method developed in this study is useful assessing not only potential of a soil to mobilise P but also, by using different poorly available P sources, the mechanisms of P mobilisation. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1007/s11104-011-1062-x Authors Ying Wang, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193 China Hasbullah, School of Agriculture, Food and Wine, The Waite Research Institute, The University of Adelaide, DX650 DP636, Adelaide, SA 5005, Australia Raj Setia, School of Agriculture, Food and Wine, The Waite Research Institute, The University of Adelaide, DX650 DP636, Adelaide, SA 5005, Australia Petra Marschner, School of Agriculture, Food and Wine, The Waite Research Institute, The University of Adelaide, DX650 DP636, Adelaide, SA 5005, Australia Fusuo Zhang, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Production of indole-3-acetic acid (IAA) by Azospirillum brasilense is one of the most important mechanisms underlying the beneficial effects observed in plants after inoculation with this bacterium. This study determined the contribution of the hisC1 gene, which encodes aromatic amino acid aminotransferase-1 (AAT1), to IAA production, and analyzed its expression in the free-living state and in association with the roots of wheat. Methods   We determined production of IAA and AAT activity in the mutant hisC::gusA-sm R . To study the expression of hisC1 , a chromosomal gene fusion was analyzed by following β-glucuronidase (GUS) activity in vitro, in the presence of root exudates, and in association with roots. Results   IAA production in the hisC mutant was not reduced significantly compared to the activity of the wild-type strain. AAT1 activity was reduced by 50% when tyrosine was used as the amino acid donor, whereas there was a 30% reduction when tryptophan was used, compared to the activity of the wild-type strain. Expression of the fusion protein was up-regulated in both logarithmic and stationary phases by several compounds, including IAA, tryptophan, tyrosine, and phenyl acetic acid. We observed the expression of hisC1 in bacteria associated with wheat roots. Root exudates of wheat and maize were able to stimulate hisC1 expression. Conclusions   The expression data indicate that hisC1 is under a positive feedback control in the presence of root exudates and on plants, suggesting that AAT1 activity plays a role in Azospirillum– plant interactions. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-1009-2 Authors Julio Castro-Guerrero, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico Angelica Romero, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico José J. Aguilar, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico Ma. Luisa Xiqui, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico Jesús O. Sandoval, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico Beatriz E. Baca, Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Av. San Claudio s/n, Ciudad Universitaria, 72570 Puebla, Mexico Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The cell wall is the main binding site of boron (B) in plants, and the differences in B requirements among different plant species are determined by pectic polysaccharide contents in the cell walls. The aim of this research was to illustrate the relationship between cell wall properties and allocation of B to cell wall and the differential sensitivity of Brassica napus cultivars to B deficiency. Methods   Two cultivars with opposite B efficiency were used to analyse the relationship among cell wall pectin contents and glycosyl composition, B uptake and allocation, gene expression and cell wall ultrastructure. Results   The Brassica napus B-efficient cultivar Qingyou 10 was more tolerant to B deficiency, exhibiting a higher biomass production, milder B deficiency symptoms and less cell wall thickening compared to the Brassica napus B-inefficient cultivar Westar 10. These differences were attributed to two factors; the first was that Qingyou 10 accumulated more B and distributed significantly higher proportion of it to the cell wall pectins than did Westar 10 under low B supply. Also, the cell walls of Qingyou 10 exhibited relatively less B-binding sites than those of Westar 10, which was indicated by the lower cell wall extraction rates, less pectin and glycosyl residue contents under the B-deficient and B-sufficient conditions. A comparison of the KDOPS gene expression levels in the two conditions suggests that Westar 10 had a higher potential for biosynthesizing B-binding substances than did Qingyou 10, regardless of B levels. Conclusions   These results suggest that both higher cell wall pectin polysaccharide content, and limited accumulation and allocation of B to the cell walls contribute to the greater sensitivity of Westar 10 to B deficiency. These two physiological aspects may determine the differences in B deficiency tolerance between Brassica napus cultivars Qingyou 10 and Westar 10. Comparably, the difference in accumulation and allocation of B to cell wall plays a much more important role than cell wall components to sensitivity difference of Brassica napus cultivars to B deficiency. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-1074-6 Authors Yuan Pan, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Zhenhua Wang, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Lu Yang, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Zhifang Wang, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Lei Shi, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Radnaa Naran, Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 3060-4712, USA Parastoo Azadi, Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 3060-4712, USA Fangsen Xu, National Key Laboratory of Crop Genetic Improvement, and Microelement Research Center, Huazhong Agricultural University, Wuhan, 430070 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Arbuscular mycorrhizal fungi (AMF) can control root-knot nematode infection, but the mode of action is still unknown. We investigated the effects of AMF and mycorrhizal root exudates on the initial steps of Meloidogyne incognita infection, namely movement towards and penetration of tomato roots. Methods   M. incognita soil migration and root penetration were evaluated in a twin-chamber set-up consisting of a control and mycorrhizal ( Glomus mosseae ) plant compartment ( Solanum lycopersicum cv. Marmande) connected by a bridge. Penetration into control and mycorrhizal roots was also assessed when non-mycorrhizal or mycorrhizal root exudates were applied and nematode motility in the presence of the root exudates was tested in vitro. Results   M. incognita penetration was significantly reduced in mycorrhizal roots compared to control roots. In the twin-chamber set-up, equal numbers of nematodes moved to both compartments, but the majority accumulated in the soil of the mycorrhizal plant compartment, while for the control plants the majority penetrated the roots. Application of mycorrhizal root exudates further reduced nematode penetration in mycorrhizal plants and temporarily paralyzed nematodes, compared with application of water or non-mycorrhizal root exudates. Conclusions   Nematode penetration was reduced in mycorrhizal tomato roots and mycorrhizal root exudates probably contributed at least partially by affecting nematode motility. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-011-1070-x Authors Christine Vos, Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (K.U.Leuven), Kasteelpark Arenberg 13, 3001 Leuven, Belgium Sofie Claerhout, Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (K.U.Leuven), Kasteelpark Arenberg 13, 3001 Leuven, Belgium Rachel Mkandawire, Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (K.U.Leuven), Kasteelpark Arenberg 13, 3001 Leuven, Belgium Bart Panis, Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (K.U.Leuven), Kasteelpark Arenberg 13, 3001 Leuven, Belgium Dirk De Waele, Laboratory of Tropical Crop Improvement, Department of Biosystems, Faculty of Bioscience Engineering, University of Leuven (K.U.Leuven), Kasteelpark Arenberg 13, 3001 Leuven, Belgium Annemie Elsen, Bodemkundige Dienst van België, Willem de Croylaan 48, 3001 Heverlee, Belgium Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   The tall fern ( Athyrium distentifolium Tausch ex Opiz) forms large stands in many deforested sites in Central European mountains. In the present study, we want to demonstrate that the effect of ferns on the leaching of nutrients is the same at low and high nitrogen (N) deposition. Methods   Free-tension lysimeters with growing ferns, and some with bare forest soil were installed in field conditions in 2006. We monitored the chemistry of lysimetric water at ambient and enhanced (plus 50 kg N ha -1 ) levels of N deposition during five growing seasons. Results   Results indicate that during the growing seasons ferns slightly decreased of acidity and conductivity of lysimetric water and substantially reduced losses of base cations (Ca 2+ and Mg 2+ ). The concentration of leached base cations was three to seven times higher from bare forest soil than from lysimeters with ferns. Higher N accumulation in fern biomass coincides with lower contents of leached N in lysimetric water. Conclusions   The reduced losses of base cations were due to the ability of Athyrium to absorb and accumulate nutrients in large amounts in living biomass and in dead undecomposed plant matter and particularly in below-ground biomass. Content Type Journal Article Category Regular Article Pages 1-14 DOI 10.1007/s11104-011-1048-8 Authors Ivan Tůma, Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, Brno, 613 00 Czech Republic Karel Fiala, Department of Vegetation Ecology, Institute of Botany, Academy of Sciences of the Czech Republic, Lidická 25, Brno, 602 00 Czech Republic Jaroslav Záhora, Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, Brno, 613 00 Czech Republic Petr Holub, Global Change Research Centre, Academy of Sciences of the Czech Republic, Bělidla 4a, Brno, 603 00 Czech Republic Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The objective of this study was to determine the relative importance of transpirational pull, Se speciation, sulfate and species on Se accumulation by plants, in order to determine which of these factors must be considered in the future development of models to predict Se accumulation by plants. Methods   Seedlings of durum wheat ( Triticum turgidum L. var durum cv ‘Kyle’) and spring canola ( Brassica napus L. var Hyola 401) were grown hydroponically and exposed to SeO 4 2- (selenate) with or without SO 4 2- (sulfate), or to HSeO 3 - (biselenite) under different transpiration regimes altered through ‘low’ (~50%) or ‘high’ (~78%) relative humidity (RH). Plants were harvested after 0, 8, 16, or 24 h exposures, digested, and analyzed for Se by GFAAS. Results   Accumulation and distribution of Se by plants is dependent on plant species, Se speciation in the nutrient solution, SO 4 2- competition, and transpiration regimes. Canola accumulated and translocated more Se than wheat. In wheat and canola, the greatest accumulation and translocation of Se occurred when plants were exposed to SeO 4 2- without SO 4 2- compared to solutions of SeO 4 2- with SO 4 2- or HSeO 3 2- . Wheat plants exposed to SeO 4 2- and SO 4 2- had an increased Se accumulation and translocation under increased transpiration rates than when exposed to SeO 4 2- without SO 4 2- or HSeO 3 2- . On the other hand, increases in transpiration increased the translocation of Se to canola shoots when exposed to HSeO 3 - more than any other treatments. Conclusions   Overall, our results suggest that plant species is the most important factor influencing Se accumulation and translocation, but that these endpoints can be modified by climate and specific soil Se or S content. Models to predict accumulation of Se by plants must consider all of these factors to accurately calculate the mechanisms of uptake and translocation. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-1069-3 Authors Heidi Renkema, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Amy Koopmans, Department of Environmental Science, Redeemer University College, Hamilton, Ontario, Canada L9K 1J4 Leanne Kersbergen, Department of Environmental Science, Redeemer University College, Hamilton, Ontario, Canada L9K 1J4 Julie Kikkert, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Beverley Hale, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada Edward Berkelaar, Department of Environmental Science, Redeemer University College, Hamilton, Ontario, Canada L9K 1J4 Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Planting density is a major factor during the conversion of cropland to woodland in the semiarid hilly region of the Chinese Loess Plateau. Jujube ( cv. Lizao on Ziziphus rootstock) tree plantations have been planted densely to increase income, with a spacing of 3 m between tree rows and 2 m between trees in rows. This practice could lead to soil water depletion. To estimate these risks, water budgets should be calculated accurately, based on a realistic characterization of root distribution. The objective of this study was to determine the spatial root distribution (vertical and horizontal) in a dense jujube plantation under different water management practices in the hilly region of the Chinese Loess Plateau. Methods   Spatial root distribution in densely planted 8-year-old jujube trees was investigated using a trench-profile method down to 1 m. Four treatments were tested: sloping land (W1), mini-catchment (W2), drip-irrigation (W3), and drip-irrigation plus mini-catchment (W4). Furthermore, mechanical excavation combined with a water spraying method was used to determine the maximum rooting depth. Results   Spatial root distribution was most affected by drip-irrigation. Horizontally, fine roots were concentrated in the area soaked by irrigation in treatments W3 (69.8%) and W4 (73.8%). Similarly, in the vertical direction, there were significantly more fine roots within the 0–1 m profile in the W4 and W3 treatments compared with the W2 and W1 treatments. Fine root intersects were even more abundant in top 0.4 m of W4 treatments compared with the whole soil profile (0–1 m depth) in the W2 and W1 treatments. The W2 and W4 treatments with mini-catchments did not result in a significantly higher number of fine root intersects relative to the treatments without catchments (W1 and W3, respectively). The correlation between fine root intersects and maximum rooting depth was analyzed and the results indicated that drip-irrigation and mini-catchment treatments increased fine root intersects, but decreased the maximum rooting depth. Conclusions   This study found that root distribution was most affected by the drip-irrigation treatment, which led to higher root densities close to water emitters on the surface, down to a depth of 0.6 m in the soil. Thus, drip-irrigation could have a significant impact on the root development of densely planted jujube trees in semiarid regions and it might potentially avoid the formation of dry soil layers. These findings provide significant support for the dense planting of jujube trees in the semiarid region. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-011-1041-2 Authors Li-hui Ma, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Northwest A&F University, Yangling, Shaanxi 712100, China Pu-te Wu, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Northwest A&F University, Yangling, Shaanxi 712100, China You-ke Wang, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Northwest A&F University, Yangling, Shaanxi 712100, China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Poplars accumulate inordinate amounts of B in their leaves and are candidate plants for the remediation of B contaminated soil. We aimed to determine the effect of heterogeneous B distribution in soil by comparing the growth and B accumulation of young Populus tremula trees growing in soil with heterogeneous and homogeneous B distributions. Methods   The first of two experiments focused on the tolerance and B accumulation of P. tremula under heterogeneous soil B distributions, while the second was designed to study fine root growth under such conditions in detail. Results   Growth and B accumulation of P. tremula were unaffected by the spatial distribution of B. Root and shoot growth were both reduced simultaneously when leaf B concentrations increased above 800 mg kg −1 . In the heterogeneous soil B treatments, root growth was more reduced in spiked soil portions with B concentrations 〉20 mg kg −1 . Fine root length growth was stronger inhibited by B stress than secondary growth. Conclusions   The root growth responses of P. tremula to B are primarily a systemic effect induced by shoot B toxicity and local toxicity effects on roots become dominant only at rather high soil B concentrations. Local heterogeneity in soil B should have little influence on the phytoremediation of contaminated sites. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1183-x Authors Rainer Rees, Institute of Terrestrial Ecosystems, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland Brett H. Robinson, Soil and Physical Sciences, Burns 222, Lincoln University, PO Box 84, Lincoln 7647, Christchurch, New Zealand Michael W. H. Evangelou, Institute of Terrestrial Ecosystems, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland Eberhard Lehmann, Spallation Neutron Source Division, Paul-Scherrer-Institut, 5232 Villigen PSI, Switzerland Rainer Schulin, Institute of Terrestrial Ecosystems, ETH Zurich, Universitätstrasse 16, 8092 Zürich, Switzerland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Rainfall is expected to show greater and more variable changes in response to anticipated rising of earth surface temperatures than most other climatic variables, and will be a major driver of ecosystem change. Methods   We studied the effects of predicted changes in California’s rainy season for storage and stabilization mechanisms of soil organic matter (SOM). In a controlled and replicated experiment, we amended rainfall over large plots of natural grassland in accordance with alternative scenarios of future climate change. Results   We found that increases in annual rainfall have important consequences for soil carbon (C) storage, but that the strength and even direction of these effects depend critically on seasonal timing. Additional rainfall during the winter rainy season led to C loss from soil while additions after the typical rainy season increased soil C content. Analysis of MIneral-Organic Matter (OM) associations reveals a potentially powerful mechanism underlying this difference: increased winter rainfall greatly diminished the role of Fe and Al oxides in SOM stabilization. Dithionite extractable crystalline Fe oxides explained more than 35% of the variability in C storage under ambient control and extended spring rainfall conditions, compared to less than 0.01% under increased winter rainfall. Likewise, poorly crystalline Fe and Al oxides explained more than 25 and 40% of the variability in C storage in the control and extended spring rainfall treatments, respectively, but less than 5% in the increased winter rainfall treatment. Conclusions   Increases in annual precipitation identical in amount but at three-month offsets produced opposite effects on soil C storage. Such clear differences in the amount and chemical composition of SOM, and in the vertical distribution of oxides in the soil profile in response to treatment timing carry important implications for the C sequestration trajectory of this ecosystem. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1156-0 Authors Asmeret Asefaw Berhe, School of Natural Sciences, University of California, Merced, 4225 N Hospital Rd Castle, Atwater, CA 95301, USA K. Blake Suttle, Grantham Institute for Climate Change & Division of Biology, Imperial College, London, UK Sarah D. Burton, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Jillian F. Banfield, Department of Earth and Planetary Sciences, University of California, Berkeley, Berkeley, CA, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Legumes of the genus Lessertia have recently been introduced to Australia in an attempt to increase the range of forage species available in Australian farming systems capable of dealing with a changing climate. This study assessed the diversity and the nodulation ability of a collection of Lessertia root nodule bacteria isolated from different agro-climatic areas of the Eastern and Western Capes of South Africa. Methods   The diversity and phylogeny of 43 strains was determined via the partial sequencing of the dnaK , 16srRNA and nodA genes. A glasshouse experiment was undertaken to evaluate symbiotic relationships between six Lessertia species and 17 rhizobia strains. Results   The dnaK and 16S rRNA genes of the majority of the strains clustered with the genus Mesorhizobium . The position of the strains at the intra-genus level was incongruent between phylogenies with few exceptions. The nodA genes from Lessertia spp. formed a cluster on their own, separate from the previously known Mesorhizobium nodA sequences. Strains showed differences in their nodulation and nitrogen fixation patterns that could be correlated with nodA gene phylogeny. L. diffusa, L. herbacea and L. excisa nodulated with nearly all the strains examined while L. capitata , L. incana and L. pauciflora were more stringent. Conclusion   Root nodule bacteria from Lessertia spp. were identified mainly as Mesorhizobium spp. Their nodA genes were unique and correlated with the nodulation and nitrogen fixation patterns of the strains. There were marked differences in promiscuity within Lessertia spp. and within strains of root nodule bacteria. Content Type Journal Article Category Regular Article Pages 1-17 DOI 10.1007/s11104-012-1153-3 Authors Macarena Gerding, Facultad de Agronomía, Universidad de Concepción, Chillán, Chile Graham William O’Hara, Centre for Rhizobium Studies, Murdoch University, Perth, Western Australia, Australia Lambert Bräu, Deakin University, School of Life and Environmental Sciences, Burwood, Australia Kemanthie Nandasena, Centre for Rhizobium Studies, Murdoch University, Perth, Western Australia, Australia John Gregory Howieson, Centre for Rhizobium Studies, Murdoch University, Perth, Western Australia, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Replacement of beech by spruce is associated with changes in soil acidity, soil structure and humus form, which are commonly ascribed to the recalcitrance of spruce needles. It is of practical relevance to know how much beech must be admixed to pure spruce stands in order to increase litter decomposition and associated nutrient cycling. We addressed the impact of tree species mixture within forest stands and within litter on mass loss and nutritional release from litter. Methods   Litter decomposition was measured in three adjacent stands of pure spruce ( Picea abies ), mixed beech-spruce and pure beech ( Fagus sylvatica ) on three nutrient-rich sites and three nutrient-poor sites over a three-year period using the litterbag method (single species and mixed species bags). Results   Mass loss of beech litter was not higher than mass loss of spruce litter. Mass loss and nutrient release were not affected by litter mixing. Litter decay indicated non-additive patterns, since similar remaining masses under pure beech (47%) and mixed beech-spruce (48%) were significantly lower than under pure spruce stands (67%). Release of the main components of the organic substance (C org , N tot , P, S, lignin) and associated K were related to mass loss, while release of other nutrients was not related to mass loss. Conclusions   In contradiction to the widely held assumption of slow decomposition of spruce needles, we conclude that accumulation of litter in spruce stands is not caused by recalcitrance of spruce needles to decay; rather adverse environmental conditions in spruce stands retard decomposition. Mixed beech-spruce stands appear to be as effective as pure beech stands in counteracting these adverse conditions. Content Type Journal Article Category Regular Article Pages 1-21 DOI 10.1007/s11104-012-1165-z Authors Torsten W. Berger, Department of Forest- and Soil Sciences, Institute of Forest Ecology, University of Natural Resources and Live Sciences (BOKU), Peter Jordan-Straße 82, 1190 Vienna, Austria Pétra Berger, Department of Forest- and Soil Sciences, Institute of Forest Ecology, University of Natural Resources and Live Sciences (BOKU), Peter Jordan-Straße 82, 1190 Vienna, Austria Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   In the long term absence of catastrophic disturbance ecosystem retrogression occurs, and this is characterized by reduced soil fertility, and impairment of plant biomass and productivity. The response of plant traits to retrogression remains little explored. We investigated how changes plant traits and litter decomposability shift during retrogression for dominant trees and understory shrubs. Methods   We characterized changes in intraspecific, interspecific and community-averaged values of plant traits and litter decomposability, for six abundant species across thirty lake islands in boreal forest that undergo retrogression with increasing time since fire. Results   For understory shrubs, trait values and litter decomposability often changed as soil fertility declined in a manner reflective of greater conservation (versus acquisition) of nutrients, particularly at the interspecific and whole community levels. Such responses were seldom observed for trees, meaning that trees and shrubs show a decoupled response to declining soil fertility during retrogression. Conclusions   Our results only partially agree with previous studies on temperate and subtropical retrogressive chronosequences. Because traits of only shrubs were responsive, they also highlight that impairment of belowground ecosystem processes during retrogression is primarily driven by changes in the trait spectra of understory vegetation rather than that of the trees. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1159-x Authors Anna Lagerström, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden Marie-Charlotte Nilsson, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden David A. Wardle, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Uptake of 90 Sr and 137 Cs in plants varies widely between soil types and between plant species. It is now recognized that the radionuclide uptake in plants is more influenced by site-specific and plant-specific parameters rather than the bulk radionuclide concentration in soil. We hypothesized that the stress which Alpine plants experience because of the short growing season may enhance the phylogenetic effect on the 137 Cs and 90 Sr transfer factors as well as the dependency of the uptake by plant to the concentrations of exchangeable Ca and K of soils. Methods   We carried out a field study on the 90 Sr and 137 Cs uptake by 11 species of Alpine plants growing on 6 undisturbed and geochemically different soils in the Alpine valley of Piora, Switzerland. Results   Results show that a strong correlation exists between the log TF and the log of exchangeable Ca or K of the soils. Conclusions   Cs uptake by Phleum rhaeticum (Poales) and Alchemilla xanthochlora (Rosales) is more sensitive to the amount of exchangeable K in the soil than the corresponding uptake by other orders. Moreover, the 90 Sr results indicate a phylogenetic effect between Non-Eudicot and Eudicots: the order Poales ( Phleum rhaeticum ) concentrating much less 90 Sr than Eudicots do. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-011-1110-6 Authors Thomas Guillaume, Institute for Radiation Physics, University Hospital Center, University of Lausanne, Lausanne, Switzerland Fabienne Chawla, Institute for Radiation Physics, University Hospital Center, University of Lausanne, Lausanne, Switzerland Philipp Steinmann, Federal Office of Public Health, Radiation Protection, Bern, Switzerland Jean-Michel Gobat, Institute of Biology, Laboratory Soil & Vegetation, University of Neuchâtel, Neuchâtel, Switzerland Pascal Froidevaux, Institute for Radiation Physics, University Hospital Center, University of Lausanne, Lausanne, Switzerland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description:    Diazotrophic species in the genus Herbaspirillum (e.g. H. frisingense , H. rubrisubalbicans and H. seropedicae ) associate with several economically important crops in the family Poaceae, such as maize ( Zea mays ), Miscanthus , rice ( Oryza sativa ), sorghum ( Sorghum bicolor ) and sugarcane ( Saccharum sp.), and can increase their growth and productivity by a number of mechanisms, including nitrogen fixation. Hence, the improvement and use of these plant growth-promoting bacteria could provide economic and environmental benefits. We review the colonization processes of host plants by Herbaspirillum spp., including histological aspects and molecular mechanisms involved in these interactions, which may be epiphytic, endophytic, and even occasionally pathogenic. Herbaspirillum can recognize plant signals that modulate the expression of colonization traits and plant growth-promoting factors. Although a large proportion of herbaspirilla remain rhizospheric and epiphytic, plant-associated species in this genus are noted for their ability to colonize the plant internal tissues. Endophytic colonization by herbaspirilla begins with the attachment of the bacteria to root surfaces, followed by colonization at the emergence points of lateral roots and penetration through discontinuities of the epidermis; this appears to involve bacterial envelope structures, such as lipopolysaccharide (LPS), exopolysaccharide (EPS), adhesins and the type three secretion system (T3SS), but not necessarily the involvement of cell wall-degrading enzymes. Intercellular spaces are then rapidly occupied, proceeding to colonization of xylem and the aerial parts of the host plants. The response of the host plant includes both the recognition of the bacteria as non-pathogenic and the induction of systemic resistance to pathogens. Phytohormone signaling cascades are also activated, regulating the plant development. This complex molecular communication between some Herbaspirillum spp. and plant hosts can result in plant growth-promotion. Content Type Journal Article Category Review Article Pages 1-22 DOI 10.1007/s11104-012-1125-7 Authors Rose Adele Monteiro, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Eduardo Balsanelli, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Roseli Wassem, Department of Genetics, Universidade Federal do Paraná, Curitiba, PR, Brazil Anelis M. Marin, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Liziane C. C. Brusamarello-Santos, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Maria Augusta Schmidt, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Michelle Z. Tadra-Sfeir, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Vânia C. S. Pankievicz, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Leonardo M. Cruz, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Leda S. Chubatsu, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Fabio O. Pedrosa, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Emanuel M. Souza, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, Curitiba, PR, Brazil Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background & aims   Plants may have dissimilar effects on ecosystem processes because they possess different attributes. Given increasing biodiversity losses, it is important to understand which plant traits are key drivers of ecosystem functions. To address this question, we studied the response of two ecosystem functions that remove nitrogen (N) from wetland soils, the accumulation of N in plant biomass and denitrification potential (DNP), to variation in plant trait composition. Methods   Our experiment manipulated plant composition in a riparian wetland. We determined relative importance of plant traits and environmental variables as predictors of each ecosystem function. Results   We demonstrate that Water Use Efficiency (WUE) had a strong negative effect on biomass N. Root porosity and belowground biomass were negatively correlated with DNP. Trait ordination indicated that WUE was largely orthogonal to traits that maximized DNP. Conclusions   These results indicate that plant species with different trait values are required to maintain multiple ecosystem functions, and provide a more mechanistic, trait-based link between the recent findings that higher biodiversity is necessary for multi-functionality. While we selected plant traits based on ecological theory, several of the plant traits were not good predictors of each ecosystem function suggesting the ecological theory linking traits to function is incomplete and requires strengthening. Content Type Journal Article Category Regular Article Pages 1-17 DOI 10.1007/s11104-011-1113-3 Authors A. E. Sutton-Grier, Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC, USA J. P. Wright, Biology Department, Duke University, Box 90338, Durham, NC, USA C. J. Richardson, Nicholas School of the Environment and Earth Sciences, Duke University, Box 90333, Durham, NC, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   The aim of this study was to compare the residual effects in soil and the influence on a flax crop ( Linum usitatissimum L.) of applying Zn from different commercial synthetic chelates. The chelates used were: Zn-EDDHSA (Zn-ethylenediamine-N,N'-bis(2-hydroxyphenylacetate), Zn-EDTA (Zn-ethylenediaminetetraacetate), Zn-HEDTA (Zn-N-2-hydroxyethyl-ethylenediaminetriacetate), Zn-EDTA-HEDTA and Zn-DTPA-HEDTA-EDTA (Zn-DTPA, Zn-diethylenetriaminepentaacetate). Methods   The experiment was conducted in a greenhouse using two different soils (Soil acid : a weakly acidic soil and Soil calc : a calcareous soil). Each treatment was administered, in a single application, to a previous flax crop at different Zn application rates. The yield and some of the flax crop quality parameters were determined in the present flax crop. Soil Zn behavior was then evaluated by single and sequential extraction. Results   In Soil acid , the Zn-HEDTA and Zn-EDDHSA fertilizers produced the highest plant parameters values (total Zn concentration, total uptake Zn), percentages of Zn utilization and values of the transfer factor, TF. In contrast, in Soil calc these fertilizers produced the lowest in-plant values, with this soil producing the highest yield, quality, percentage of utilization and TF associated with the application of Zn-DTPA-HEDTA-EDTA and Zn-EDTA fertilizers. However, the Zn-EDTA in Soil acid and Zn-DTPA-HEDTA-EDTA in Soil calc , were associated with the greatest amounts of bioavailable Zn in soil and also with the highest Zn concentrations associated with the sum of the most labile fractions (water soluble plus exchangeable fractions). Conclusions   The residual Zn produced by the different fertilizer treatments estimated using the DTPA, Mehlich-3- and LMWOAs methods- was available in sufficient quantities that it not be necessary to add any further Zn (which could have resulted in over-fertilization) for the subsequent crop to either of the soils. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1502-2 Authors Patricia Almendros, Chemistry and Agricultural Analysis Department, College of Agriculture, Technical University of Madrid (UPM), Ciudad Universitaria s.n., 28040 Madrid, Spain Demetrio Gonzalez, Chemistry and Agricultural Analysis Department, College of Agriculture, Technical University of Madrid (UPM), Ciudad Universitaria s.n., 28040 Madrid, Spain Jose M. Alvarez, Chemistry and Agricultural Analysis Department, College of Agriculture, Technical University of Madrid (UPM), Ciudad Universitaria s.n., 28040 Madrid, Spain Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Can hydraulic traits be used to predict sensitivity of drought-prone forests to crown decline and tree mortality? Content Type Journal Article Category Commentary Pages 1-3 DOI 10.1007/s11104-012-1508-9 Authors Rafael S. Oliveira, Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, 13083-862 SP, Brazil Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   In post mining landscapes as in the Lusatian region (Brandenburg, Germany), Pleistocene coarse-textured, sandy sediments are used for soil rehabilitation and land reclamation. The homogeneously-appearing initial soils are characterized by finer-textured soil clumps (fragments) of different sizes that are embedded in a sandy matrix. These soils with typical local-scale heterogeneity may serve as a model for studying how spatially-distributed soil fragments may be utilized by pioneering plant species. The aim of this study was to gain insight into the physical and chemical properties of sandy matrix and fragments that could possibly explain why embedded fragment may act as hot spots for root growth. Methods   In 2009, three soil monoliths of dimension 50 cm × 50 cm × 50 cm that were exclusively vegetated by Lotus corniculatus L. planted in 2008 were studied. Each layer of 10 cm was sampled successively using a cubic metal frame with 10 cm edge length (25 samples per layer each with a volume of 1 l). The samples were analyzed for root biomass, root lengths and diameter, and for chemical and physical properties of sandy matrix and fragments. Results   Bulk density, water contents, total carbon, total nitrogen, and plant available calcium contents were higher for the fragments compared to the sandy matrix. The roots of L. corniculatus were heterogeneously distributed in the monoliths. The root density distributions for the 1 L samples indicated a positive influence of fragments on directed root growth. Fragments embedded in the sandy matrix were found to be strongly penetrated by roots despite their relatively high bulk density. The presence of fragments also led to an increased root biomass in the sandy matrix in the direct vicinity of fragments. Such direct effects on root development were accompanied by more indirect effects by locally-elevated moisture and nutrient contents. Conclusion   The results suggest that finer-textured fragments embedded in coarser-textured sediments, can have favorable effect on plant and root development during the initial stages of establishment of vegetation cover. The fragments can act as water and nutrient hot spots to improve supply of pioneering plants especially in coarse-textured soil. The existence of small-scale heterogeneities owing to incomplete sediment mixing e.g., in soil reclamation, could be generally important for controlling the speed and direction of early plants-establishment, for instance, in the succession of post-mining areas. Content Type Journal Article Category Regular Article Pages 1-16 DOI 10.1007/s11104-012-1505-z Authors Katja M. Boldt-Burisch, Soil Protection and Recultivation, Brandenburg University of Technology, 03046 Cottbus, Germany Horst H. Gerke, Institute of Soil Landscape Research, Leibniz-Centre for Agricultural Landscape Research (ZALF), Müncheberg, Eberswalder Straße 84, 15374 Müncheberg, Germany Seth Nii-Annang, Soil Protection and Recultivation, Brandenburg University of Technology, 03046 Cottbus, Germany Bernd Uwe Schneider, Helmholtz Centre Potsdam – German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany Reinhard F. Hüttl, Soil Protection and Recultivation, Brandenburg University of Technology, 03046 Cottbus, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Potatoes have an inadequate rooting system for efficient acquisition of water and minerals and use disproportionate amounts of irrigation and fertilizer. This research determines whether significant variation in rooting characteristics of potato exists, which characters correlate with final yield and whether a simple screen for rooting traits could be developed. Methods   Twenty-eight genotypes of Solanum tuberosum groups Tuberosum and Phureja were grown in the field; eight replicate blocks to final harvest, while entire root systems were excavated from four blocks. Root classes were categorised and measured. The same measurements were made on these genotypes in the glasshouse, 2 weeks post emergence. Results   In the field, total root length varied from 40 m to 112 m per plant. Final yield was correlated negatively with basal root specific root length and weakly but positively with total root weight. Solanum tuberosum group Phureja genotypes had more numerous roots and proportionally more basal than stolon roots compared with Solanum tuberosum , group Tuberosum genotypes. There were significant correlations between glasshouse and field measurements. Conclusions   Our data demonstrate that variability in rooting traits amongst commercially available potato genotypes exists and a robust glasshouse screen has been developed. By measuring potato roots as described in this study, it is now possible to assess rooting traits of large populations of potato genotypes. Content Type Journal Article Category Regular Article Pages 1-19 DOI 10.1007/s11104-012-1483-1 Authors Jane Wishart, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TS, UK Timothy S. George, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK Lawrie K. Brown, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK Gavin Ramsay, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK John E. Bradshaw, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK Philip J. White, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK Peter J. Gregory, East Malling Research, New Road, East Malling ME19 6BJ, UK Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   This study was conducted to reveal the genetic diversity of common bean ( Phaseolus vulgaris L.) nodulating rhizobia in various agroecological regions in Nepal. Method   A total of 63 strains were isolated from common bean grown in the soils collected from seven bean fields in Nepal and characterized based on the partial sequences of 16S–23S internal transcribed spacer (ITS) regions, 16S rDNA, nodC , and nifH . Symbiotic properties of some representative strains with host plants were examined to elucidate their characteristics in relation to genotype and their origin. Results   The isolated strains belonged to Rhizobium leguminosarum , Rhizobium etli , Rhizobium phaseoli , and one unknown Rhizobium lineage, all belonging to a common symbiovar (sv.) phaseoli . Nine ITS genotypes were detected mainly corresponding to a single site, including a dominant group at three sites harboring highly diverse multiple ITS sequences. Three symbiotic genotypes corresponded to a geographical region, not to the ribosomal DNA group, suggesting horizontal transfer of symbiotic genes separately in each region. Great differences in nitrogenase activity and nodule forming ability among the strains irrespective of their species and origin were observed. Conclusions   Nepalese Himalaya harbor phylogenetically highly diverse and site-specific strains of common bean rhizobia, some of which could have high potential of symbiotic nitrogen fixation. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1518-7 Authors Dinesh Adhikari, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan Kazuhito Itoh, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan Kousuke Suyama, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Replant problems or soil sickness are known phenomena but still unsolved. The aims of this study were (i) to set up a test system for detecting replant problems using in vitro propagated apple rootstocks (M26) based on different soil disinfection treatments and (ii) to explore the treatment effects on root morphology and soil microbial community structure. Methods   The bio-test involved soil with apple replant problems (apple sick) and healthy soil from an adjacent plot, both either untreated, or submitted to treatments of 50 and 100 °C, or the chemical soil disinfectant Basamid. Histological analyses of roots and denaturing gradient gel electrophoresis (DGGE) fingerprints in rhizosphere soil collected at the final evaluation were performed. Results   After 10 weeks, shoot dry mass on apple sick soil was 79, 108 and 124 % higher for soil treated at 50 °C, 100 °C and with Basamid, respectively, compared to the untreated soil. Roots in untreated apple sick soil showed destroyed epidermal and cortical layers. DGGE fingerprints revealed treatment dependent differences in community composition and relative abundance of total bacteria, Bacillus , Pseudomonas and total fungi. Conclusions   The clear differences detected in soil microbial communities are the first steps towards a better understanding of the causes for apple replant problems. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1454-6 Authors Bunlong Yim, Leibniz Universität Hannover—Institute of Floriculture and Woody Plant Science, Tree Nursery Science Section, Herrenhäuser Str. 2, 30419 Hannover, Germany Kornelia Smalla, Julius Kühn-Institut, Institute for Epidemiology and Pathogen Diagnostics, Messeweg 11-12, 38104 Braunschweig, Germany Traud Winkelmann, Leibniz Universität Hannover—Institute of Floriculture and Woody Plant Science, Tree Nursery Science Section, Herrenhäuser Str. 2, 30419 Hannover, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Root decomposition studies have rarely considered the heterogeneity within a fine-root system. Here, we investigated fine root (〈 0.5 and 0.5–2 mm in diameter) decomposition and accompanying nutrient dynamics of two temperate tree species— Betula costata Trautv and Pinus koraiensis Sieb. et Zucc. Methods   Both litterbag and intact-core techniques were used to examine decomposition dynamic and nutrient release of the two size class roots over a 498-day period. Moreover, we examined differences between the two approaches. Results   The very fine roots (〈 0.5 mm) with an initially lower C:N ratio, decomposed more slowly than 0.5–2 mm roots of both tree species. The differences in mass loss between size classes were smaller when using the intact-core technique compared with litterbag technique. In contrast to root biomass loss, net N release was much higher in the fine roots (〈 0.5 mm). All fine roots initially released N (0–75 days), but immobilized N to varying extent in the following days (75–498 days) during decomposition. Conclusions   Our results suggest that the slow decomposition rate of very fine roots (〈 0.5 mm) may be determined by their high concentration of acid-unhydrolyzable structural components. Additionally, the heterogeneity within a bulk fine-root system could lead to differences in their contribution to soil in terms of carbon and nitrogen dynamics. Content Type Journal Article Category Regular Article Pages 1-14 DOI 10.1007/s11104-012-1457-3 Authors Tao Sun, Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040 People’s Republic of China Zijun Mao, Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040 People’s Republic of China Lili Dong, Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040 People’s Republic of China Lingling Hou, Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040 People’s Republic of China Yuan Song, Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040 People’s Republic of China Xiuwei Wang, School of Forestry, Northeast Forestry University, Harbin, 150040 People’s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Several strains of rhizobacteria may be found in the rhizospheric soil, on the root surface or in association with rice plants. These bacteria are able to colonize plant root systems and promote plant growth and crop yield through a variety of mechanisms. The objectives of this study were to isolate, identify, and characterize putative plant growth-promoting rhizobacteria (PGPR) associated with rice cropped in different areas of southern Brazil. Methods   Bacterial strains were selectively isolated based on their growth on three selective semi-solid nitrogen-free media. Bacteria were identified at the genus level by PCR-RFLP 16S rRNA gene analysis and partial sequencing methodologies. Bacterial isolates were evaluated for their ability to produce indolic compounds and siderophores and to solubilize phosphate. In vitro biological nitrogen fixation and the ability to produce 1-aminocyclopropane-1-carboxylate deaminase were evaluated for each bacterial isolate used in the inoculation experiments. Results   In total, 336 bacterial strains were isolated representing 31 different bacterial genera. Strains belonging to the genera Agrobacterium, Burkholderia, Enterobacter, and Pseudomonas were the most prominent isolates. Siderophore and indolic compounds producers were widely found among isolates, but 101 isolates were able to solubilize phosphate. Under gnotobiotic conditions, eight isolates were able to stimulate the growth of rice plants. Five of these eight isolates were also field tested in rice plants subjected to different nitrogen fertilization rates. Conclusions   The results showed that the condition of half-fertilization plus separate inoculation with the isolates AC32 ( Herbaspirillum sp.), AG15 ( Burkholderia sp.), CA21 ( Pseudacidovorax sp.), and UR51 ( Azospirillum sp.) achieved rice growth similar to those achieved by full-fertilization without inoculation, thus highlighting the potential of these strains for formulating new bioinoculants for rice crops. Content Type Journal Article Category Regular Article Pages 1-19 DOI 10.1007/s11104-012-1430-1 Authors Rocheli de Souza, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Caixa Postal 15.053, Prédio 43312, sala 207b, Porto Alegre, RS CEP 91501-970, Brasil Anelise Beneduzi, Fundação Estadual de Pesquisa Agropecuária (FEPAGRO), Rua Gonçalves Dias 570, 90130-060 Porto Alegre, RS, Brasil Adriana Ambrosini, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Caixa Postal 15.053, Prédio 43312, sala 207b, Porto Alegre, RS CEP 91501-970, Brasil Pedro Beschoren da Costa, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Caixa Postal 15.053, Prédio 43312, sala 207b, Porto Alegre, RS CEP 91501-970, Brasil Jacqueline Meyer, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Caixa Postal 15.053, Prédio 43312, sala 207b, Porto Alegre, RS CEP 91501-970, Brasil Luciano K. Vargas, Fundação Estadual de Pesquisa Agropecuária (FEPAGRO), Rua Gonçalves Dias 570, 90130-060 Porto Alegre, RS, Brasil Rodrigo Schoenfeld, Instituto Riograndense do Arroz (IRGA), Avenida Bonifácio Carvalho Bernardes 1494, 94930-030 Cachoeirinha, RS, Brasil Luciane M. P. Passaglia, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500, Caixa Postal 15.053, Prédio 43312, sala 207b, Porto Alegre, RS CEP 91501-970, Brasil Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   This study explored molecular mechanism of ascorbic acid (AsA)-mediated enhancement of plant tolerance against cadmium (Cd) stress. Methods   Complex pharmacological, histochemical and molecular approaches were applied to analyse the effect of AsA on the alleviation of Cd stress and corresponding signalling pathway. Results   Cd stress brought about severe oxidative damage and remarkable decrease in AsA content in alfalfa (Medicago sativa) seedling roots. Exogenous AsA not only increased AsA content in vivo, and strengthened the up-regulation of alfalfa heme oxygenase-1 (HO-1) transcript and HO activity triggered by Cd, but also significantly decreased Cd accumulation and oxidative damage, which was confirmed by the histochemical analysis. The responses of AsA were further impaired by the potent inhibitor of HO-1, zinc protoporphyrin IX (ZnPP), which were blocked further when 50 % saturation of carbon monoxide (CO) aqueous solution (in particular) or bilirubin (BR), two catalytic by-products of HO-1, was added, respectively. Molecular evidence illustrated that AsA-triggered the up-regulation of antioxidant enzyme genes, especially Mn-SOD and POD , were sensitive to ZnPP and reversed by CO. Conclusions   In short, above results suggested that cytoprotective roles triggered by AsA might be, at least partially, through HO-1-dependent fashion by the induction of antioxidant system and lowering Cd accumulation. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-012-1451-9 Authors Qijiang Jin, College of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Jiangsu Province, Nanjing Agricultural University, Nanjing, 210095 People,s Republic of China Kaikai Zhu, College of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Jiangsu Province, Nanjing Agricultural University, Nanjing, 210095 People,s Republic of China Yanjie Xie, College of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Jiangsu Province, Nanjing Agricultural University, Nanjing, 210095 People,s Republic of China Wenbiao Shen, College of Life Sciences, Co. Laboratory of Nanjing Agricultural University and Carl Zeiss Far East, Jiangsu Province, Nanjing Agricultural University, Nanjing, 210095 People,s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   The beneficial effects of Si have mainly been observed in herbaceous plants, while little is known about its role in deciduous trees. The aim of this work was to evaluate the effect of foliar application of Si on chestnut leaf growth, photosynthesis and water relations in the presence of short, but intense water deficit. Methods   Sili-K® solution (containing 0.12 % Si and 0.15 % K) was repeatedly (× 3) sprayed onto leaves of potted chestnut plantlets and irrigation was suspended 7 weeks later, for 8 days. Leaf growth, anatomy, as well as physiological and biochemical traits of the plantlets were studied. Results   Si application enhanced chestnut growth, due to increased photosynthetic traits, including higher chlorophyll content and chlorophyll a to b ratio, photochemical efficiency of PSII, gas exchange (stomatal conductance, transpiration rate, net CO 2 assimilation) and oxygen evolution rate. Meanwhile, Si yielded larger and thinner leaves, higher xylem, specific leaf area and transpiration rate, thus being beneficial to the tree in absorbing sunlight energy for photosynthesis and in alleviating heat stress. However, Si also lowered leaf sap osmotic pressure, causing the plant to lose water more quickly, thus being more susceptible to water stress. Conclusions   Si improved chestnut photosynthesis, growth, and heat stress tolerance, but it also increased the susceptibility to drought. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1385-2 Authors Changhe Zhang, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal José M. Moutinho-Pereira, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal Carlos Correia, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal João Coutinho, Centre of Chemistry (CQ)/Department of Soil Science, Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal António Gonçalves, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal Américo Guedes, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal José Gomes-Laranjo, Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB)/Department of Biological and Environmental Engineering (DeBA), Universidade de Trás-os-Montes e Alto Douro, Apt. 1013, 5001-801 Vila Real, Portugal Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Aluminum-tolerant wheat plants often produce more root exudates such as malate and phosphate than aluminum-sensitive ones under aluminum (Al) stress, which provides environmental differences for microorganism growth in their rhizosphere soils. This study investigated whether soil bacterial community composition and abundance can be affected by wheat plants with different Al tolerance. Methods   Two wheat varieties, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive), were grown for 60 days in acidic soils amended with or without CaCO 3 . Plant growth, soil pH, exchangeable Al content, bacterial community composition and abundance were investigated. Results   Atlas 66 showed better growth and lower rhizosphere soil pH than Scout 66 irrespective of CaCO 3 amendment or not, while there was no significant difference in the exchangeable Al content of rhizosphere soil between the two wheat lines. The dominant bacterial community composition and abundance in rhizosphere soils did not differ between Atlas 66 and Scout 66, although the bacterial abundance in rhizosphere soil of both wheat lines was significantly higher than that in bulk soil. Sphingobacteriales , Clostridiales , Burkholderiales and Acidobacteriales were the dominant bacteria phylotypes. Conclusions   The difference in wheat Al tolerance does not induce the changes in the dominant bacterial community composition or abundance in the rhizosphere soils. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1007/s11104-012-1473-3 Authors Chao Wang, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Xue Qiang Zhao, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Rong Fu Chen, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Hai Yan Chu, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Ren Fang Shen, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   The aim of this study is to enhance our knowledge of nitrogen (N) cycling and N acquisition in tropical montane forests through analysis of stable N isotopes (δ 15 N). Methods   Leaves from eight common tree species, leaf litter, soils from three depths and roots were sampled from two contrasting montane forest types in Jamaica (mull ridge and mor ridge) and were analysed for δ 15 N. Results   All foliar δ 15 N values were negative and varied among the tree species but were significantly more negative in the mor ridge forest (by about 2 ‰). δ 15 N of soils and roots were also more negative in mor ridge forests by about 3 ‰. Foliar δ 15 N values were closer to that of soil ammonium than soil nitrate suggesting that trees in these forests may have a preference for ammonium; this may explain the high losses of nitrate from similar tropical montane forests. There was no correlation between the rankings of foliar δ 15 N in the two forest types suggesting a changing uptake ratio of different N forms between forest types. Conclusions   These results indicate that N is found at low concentrations in this ecosystem and that there is a tighter N cycle in the mor ridge forest, confirmed by reduced nitrogen availability and lower rates of nitrification. Overall, soil or root δ 15 N values are more useful in assessing ecosystem N cycling patterns as different tree species showed differences in foliar δ 15 N between the two forest types. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-012-1469-z Authors Francis Q. Brearley, Department of Botany, Trinity College, University of Dublin, Dublin 2, Ireland Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Explore how soil CO 2 efflux and its components change after moving sand dunes are stabilized with shrubs, and how abiotic factors affect those components at different scales. Methods   Soil CO 2 efflux from a sand-stabilized area was compared to that from moving sand dunes in the Tengger Desert. To partition rhizosphere respiration (R R ) from soil basal respiration (R B ), a root-isolation plot was established. Results   Compared to moving sand dunes, total soil respiration (R T ) in the sand-stabilized area increased 3.2 fold to 0.28 ± 0.08 μmol CO 2 m -2  s -1 , two thirds of which was from R B . Shrub patchiness produced spatial variation in soil respiration, whereas temporal dynamics of soil respiration were affected mainly by soil water content. Shallow soil water content (0–20 cm) influenced R T and R B , whereas deep soil water content (30–210 cm) influenced R R and the ratio R R /R T . During most of the year when soil water content was below field capacity, diurnal changes in soil respiration were partially decoupled from soil temperature but could be modeled using soil temperature and photosynthetic active radiation. Conclusions   Sand-dune stabilization increased soil respiration, and increased R B from biological soil crust and altered soil properties such as increased soil organic matter contributed more than increased R R from increased shrubs. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1465-3 Authors Zhi-Shan Zhang, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Xin-Rong Li, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Robert S. Nowak, Department of Natural Resources and Environmental Science, Mail Stop 186, University of Nevada Reno, Reno, NV 89557, USA Pan Wu, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Yan-Hong Gao, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Yang Zhao, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Lei Huang, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Yi-Gang Hu, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Rong-Liang Jia, Shapotou Desert Research and Experimental Station, Cold and Arid Region Environmental and Engineering Research Institute, Chinese Academy of Sciences, Donggang West Road 320, Lanzhou, 730000 People’s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background   Magnesium (Mg), as an essential mineral element for plants and microbes, can have both indirect as well as direct effects on disease. Balanced nutrition is critical for the expression of disease resistance since nutrition is part of a delicately balanced interdependent system influenced by the plant’s genetics and the environment. A deficiency or excess of Mg can influence a wide range of physiologic functions because of these interrelated processes. Scope   There are fewer reports of direct effects of Mg deficiency or excess on plant disease than for many elements because of its participation in a wide spectrum of general physiological functions so that individual activities involved in defense, virulence, or pathogenesis are not as easily characterized. The ability of Mg to compliment or antagonize other minerals can result in different disease responses to Mg under varying environmental conditions. Fusarium wilt pathogens tend to be less severe when adequate Mg is available, and Mg increases resistance of tissues to degradation by some pectolytic enzymes of macerating or soft rotting pathogens. In contrast, high rates of Mg that interfere with Ca uptake may increase the incidence of diseases such as bacterial spot of tomato and pepper or peanut pod rot. Conclusions   The more general physiological benefits of Mg for active growth often obscure specific mechanisms involved in resistance to disease, although Mg is an important contributor to over-all plant health. A specific mechanism of defense to diseases enhanced by Mg includes increased resistance of tissues to degradation by pectolytic enzymes of bacterial soft rotting pathogens. Management of Mg nutrition to reduce disease, in balance with other minerals, is an underutilized tool for disease control. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1476-0 Authors Don M. Huber, Purdue University, West Lafayette, IN, USA Jeff B. Jones, University of Florida, IFAS, Gainesville, FL, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Soil carbon storage is an important component of global carbon cycling. Andean Andisols have high carbon content and are vulnerable to erosion because of agricultural intensification and deforestation. This study examines the effects of land use on erosion and soil carbon storage in the Río Chimbo watershed of Ecuador. Methods   Soil carbon content, age, and erosion estimated from 137 Cs inventories was measured along an elevational transect under annual cropping, natural forest, páramo, pasture, and tree plantations. Results   Land use, particularly annual cropping, affected 137 Cs levels in the upper soil layers, but did not have an impact on total carbon storage to a depth of 1 m. Relative erosion rates estimated from 137 Cs inventories at sites under annual cropping averaged 27 t ha −1  y −1 over the erosion rate of non-cultivated sites. A linear relationship was observed between soil carbon age (determined by 14 C levels) and 137 Cs levels, where pasture sites had lower 137 Cs and older carbon compared to natural forest sites. Conclusions   The effects of land use on soil loss in the Río Chimbo watershed suggest a loss and/or removal of soil carbon, particularly under annual cropping. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1478-y Authors A. Henry, Intercollege Program in Plant Biology, The Pennsylvania State University, University Park, PA 16802, USA L. Mabit, Environmental Geosciences, Department of Environmental Sciences, University of Basel, Basel, Switzerland R. E. Jaramillo, Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA Y. Cartagena, Instituto Nacional Autónomo de Investigaciones Agropecuarias, Estación Experimental Santa Catalina, Quito, Ecuador J. P. Lynch, Intercollege Program in Plant Biology, The Pennsylvania State University, University Park, PA 16802, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Effects of final harvest of plantations and re-conversion with different tillage intensities on quantity and distribution of organic matter in different soil fractions were assessed. Methods   A field trial was conducted at two poplar and one willow plantation in northern Germany. Distribution of C in aboveground plant and root biomass and within various soil fractions (particulate organic matter, water-stable aggregates, microbial biomass) was determined. Directly after re-conversion, which was performed at tillage depths of 5, 15 and 30 cm, C amounts added with coarse harvest residues and changes in soil C fractions were examined. Results   Plantation C stocks decreased in the order soil 〉 aboveground biomass 〉 roots. After re-conversation no change in bulk soil SOC but an increase of labile soil C was observed. Between 16 and 30 t ha −1 additional C was determined in the soil fraction of plant residues 〉2 mm after re-conversion. Up to 90 % SOC of the fine earth fraction was associated with macroaggregates, which increased after re-conversion despite intensive tillage with a rotary cultivator. Conclusion   The duration of the increased macroaggregate associated C directly after soil tillage is a short term effect of the tillage. The influence of tillage depths on soil C-fractions could be observed only in some cases because of the high variability of harvest residues in the field. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-012-1481-3 Authors Charlotte Toenshoff, Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstr. 1a, 37213 Witzenhausen, Germany Reinhold Stuelpnagel, Department of Grassland Science and Renewable Plant Resources, University of Kassel, Steinstr. 19, 37213 Witzenhausen, Germany Rainer Georg Joergensen, Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstr. 1a, 37213 Witzenhausen, Germany Christine Wachendorf, Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstr. 1a, 37213 Witzenhausen, Germany Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Rising costs and pressure on supplies of commercial mineral fertilizers and increasing markets for organically produced foods and feeds have led to a growing interest in soil amendments to supply plant nutrients. Rockdust is a by-product of quarrying and its effectiveness to supply plants with nutrients has been a contested issue and there have been no assessments of its effect on soil biota other than plants. The aim of this study was to assess the effect of a commercially-available volcanic rockdust application on crop growth and element concentrations for a wide range of macro and microelements and the response of soil microbial communities to rockdust due to the potential alteration in soil mineralogy. Methods   A three-year controlled outdoor-growing experiment was conducted on three different soil types with two wheat cultivars in the first year following rockdust application and with forage species in the third year. Results   Our results show that the tested rockdust had no positive or negative effect on plant growth or nutrient composition. In addition, the microbial response to added substrates, a sensitive measure of changes in soil environment, were unaltered by the rockdust. Conclusions   As the rockdust had no nutrient or toxic effect it can probably be considered as an inert material which at least causes no harm but equally has no demonstrable ecological or agricultural benefit. Content Type Journal Article Category Regular Article Pages 1-18 DOI 10.1007/s11104-012-1474-2 Authors Atefeh Ramezanian, Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Box 7043, Ulls väg 16, 750 07 Uppsala, Sweden A. Sigrun Dahlin, Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, 750 07 Uppsala, Sweden Colin D. Campbell, Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, 750 07 Uppsala, Sweden Stephen Hillier, The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH Scotland, UK Birgitta Mannerstedt-Fogelfors, Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Box 7043, Ulls väg 16, 750 07 Uppsala, Sweden Ingrid Öborn, Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Box 7043, Ulls väg 16, 750 07 Uppsala, Sweden Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Copper (Cu) is an essential micronutrient required for growth and development of plants. However, excess Cu is toxic to plants. To understand the mechanisms involved in copper stress response, a proteomic approach was used to investigate the differences in Cu stress-induced protein expression between a Cu-tolerant variety (B1139) and a Cu-sensitive one (B1195) of rice. Methods   Rice seedlings were exposed to 8 μM Cu for 3 days, with plants grown in the normal nutrient solution containing 0.32 μM Cu serving as the control. Proteins were extracted from the roots and separated by two-dimensional PAGE. Thirty four proteins were identified using MALDI-TOF mass spectrometry. Results   Thirty-four protein spots were found to be differently expressed in the Cu-stressed roots in at least one variety of rice, including those involved in antioxidative defense, redox regulation, stress response, sulfur and glutathione (GSH) metabolism, carbohydrate metabolism, signal transduction, and some other proteins with various functions. Nine proteins, including putative cysteine synthase, probable serine acetyltransferase 3, L-ascorbate peroxidase 1, putative glutathione S-transferase 2, and thioredoxin-like 3-3, exhibited a greater increase in response to Cu stress in the Cu-tolerant variety B1139 compared with the Cu–sensitive variety B1195. Conclusion   The majority of the proteins showing differential expression in response to Cu exposure are involved in the redox regulation, and sulfur and GSH metabolism, suggesting that these proteins, together with antioxidant enzymes, play an important role in the detoxification of excess Cu and maintaining cellular homeostasis. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-012-1458-2 Authors Yufeng Song, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 the People’s Republic of China Jin Cui, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 the People’s Republic of China Hongxiao Zhang, College of Agricultural, Henan University of Science and Technology, Luoyang, 471003 the People’s Republic of China Guiping Wang, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 the People’s Republic of China Fang-Jie Zhao, College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing, 210095 the People’s Republic of China Zhenguo Shen, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 the People’s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Bioavailable phosphorus (P) represents a primary constraint on productivity in many ecosystems on highly-weathered soils. Soil moisture can be important to determining P bioavailability and net primary productivity in these systems. However, hydrologic controls on P availability remain poorly understood. Methods   We used “resins” (anion-exchange membranes) to quantify the response of labile P, an estimate of bioavailable P, to soil moisture conditions in two highly-weathered soils (rendzina, ultisol). The resins were either incubated in soil or shaken with a soil-water slurry. Results   Resin incubations in aerobic soil effectively quantified labile P in soils under changing moisture conditions, extracting significant amounts of labile P while avoiding the disturbance imposed by slurries. Wetting field-moist soils resulted in pulsed labile P, with lagged peaks occurring days after the largest moisture additions. Re-wetting air-dried soils enhanced labile P immediately, with the largest amounts observed at the highest moisture levels; labile P steadily declined following the moisture addition. Conclusions   Soil moisture levels and history strongly impacted labile P, indicating the importance of both variables when interpreting labile P measurements. These results also suggest that P availability is linked to both the amount and timing of rainfall, with implications for plant productivity in regions exposed to changing moisture regimes. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1007/s11104-012-1373-6 Authors Marcia DeLonge, Department of Environmental Sciences, University of Virginia, PO Box 400123, Charlottesville, VA 22904-4123, USA Karen L. Vandecar, Department of Environmental Sciences, University of Virginia, PO Box 400123, Charlottesville, VA 22904-4123, USA Paolo D’Odorico, Department of Environmental Sciences, University of Virginia, PO Box 400123, Charlottesville, VA 22904-4123, USA Deborah Lawrence, Department of Environmental Sciences, University of Virginia, PO Box 400123, Charlottesville, VA 22904-4123, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   We developed a method for processing roots from soil cores and monoliths in the laboratory to reduce the time and cost devoted to separating roots from debris and improve the accuracy of root variable estimates. The method was tested on soil cores from a California oak savanna, with roots from trees, Quercus douglasii, and annual grasses. Methods   In the randomized sampling method, one isolates the sample fraction consisting of roots and organic debris 〈 = 1 cm in length, and randomizes it through immersion in water and vigorous mixing. Sub-samples from the mixture are then used to estimate the percentage of roots in this fraction, thereby enabling an estimate of total sample biomass. Results   We found that root biomass estimates, determined through the randomization method, differed from total root biomass established by meticulously picking every root from a sample with an error of 3.0 % +/− 0.6 % s.e. Conclusions   This method greatly reduces the time and resources required for root processing from soil cores and monoliths, and improves the accuracy of root variable estimates compared to standard methods. This gives researchers the ability to increase sample frequency and reduce the error associated with studying roots at the landscape and plant scales. Content Type Journal Article Category Regular Article Pages 1-16 DOI 10.1007/s11104-012-1350-0 Authors Laura E. Koteen, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, USA Dennis D. Baldocchi, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention. Methods   Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t ha -1 in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50 % of the recommended rate (108 kg N ha -1 ). Nitrogen fertilizer enriched with 15  N was applied in 2009 to the 0 and 12 t ha -1 of biochar at 100 and 50 % secondary N application. Results   Maize yield and plant N uptake did not change with biochar additions ( p  〉 0.05; n  = 3). Less N (by 82 %; p  〈 0.05) was lost after biochar application through leaching only at 100 % N fertilization. The reason for an observed 140 % greater retention of applied 15  N in the topsoil may have been the incorporation of added 15  N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer 15  N (0.42 % of applied N; p  〈 0.05) and comparatively high recovery of applied 15  N in the soil (39 %) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar. Conclusions   Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil. Content Type Journal Article Category Regular Article Pages 1-16 DOI 10.1007/s11104-012-1383-4 Authors David Güereña, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA Johannes Lehmann, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA Kelly Hanley, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA Akio Enders, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA Charles Hyland, Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA Susan Riha, Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   Efficient accumulation of arsenic (As) in rice ( Oryza sativa L.) poses a potential health risk to rice consumers. The aim of this study was to investigate the mechanisms of uptake, transport and distribution of inorganic arsenic (As i ) and dimethylarsinic acid (DMA) in rice plants. Methods   Rice was exposed to As i (As(V)) and DMA in hydroponics. High-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and synchrotron X-ray fluorescence (SXRF) microprobe were used to determine As concentration and the in situ As distribution. Results   DMA induced abnormal florets before flowering and caused a sharp decline in the seed setting rate after flowering compared to As i . Rice grains accumulated 2-fold higher DMA than As i . The distribution of As i concentration (root 〉 leaf 〉 husk 〉 caryopsis) in As(V) treatments was different from that of the DMA concentration (caryopsis 〉 husk 〉 root ≥ leaf) in DMA treatments. SXRF showed that As i mainly accumulated in the vascular trace of caryopsis with limited distribution to the endosperm, whereas DMA was observed in both tissues. Conclusions   DMA tended to accumulate in caryopsis and induced higher toxicity to the reproductive tissues resulting in markedly reduced grain yield, whereas As i mainly remained in the vegetative tissues and had no significant effect on yield. DMA is more toxic than As i to the reproductive tissues when both of them are at similar concentrations in nutrient solution. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-012-1376-3 Authors Mao-Zhong Zheng, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021 China Gang Li, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021 China Guo-Xin Sun, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 China Hojae Shim, University of Macau, Taipa, Macau SAR, China Chao Cai, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Common bean is a major source of protein for many people worldwide. However, the crop is often subjected to drought conditions and its advantage in undertaking symbiotic nitrogen fixation can be severely decreased. The primary objective of this study was to compare the resistance of nitrogen fixation of 12 selected genotypes to soil drying. Methods   Twelve common bean genotypes of diverse genetic background were compared. Plants were grown in pots and subjected to soil drying over about 2 weeks. Nitrogen fixation was measured daily using a flow-through acetylene reduction technique. The plants were exposed to acetylene for only a short time period allowing repeated measures. The acetylene reduction rate of plants on drying soil was normalized against the rates measured for well-watered plants. Results   Substantial variability was identified among genotypes in the threshold soil water content at which nitrogen fixation was observed to decrease. Genotypes SER 16, SXB 412, NCB 226, and Calima were found to have the greatest delay in their decrease in nitrogen fixation rates based on soil water content. These four genotypes expressed substantial tolerance of nitrogen fixation to soil drying. These experiments also resulted in data on the threshold soil water contents at which transpiration rates decreased. A decrease in transpiration rates at high soil water contents is potentially advantageous since it allows soil water conservation for use as the severity of the drought increases. There was a general trend of those genotypes with sustained nitrogen fixation rates to low soil water contents also expressing decreased transpiration rates at high soil water contents. Conclusions   This study identified genetic variation among common bean genotypes in their response of nitrogen fixation and transpiration to soil drying. Five genotypes (SER 16, SXB 412, NCB 226, Calima, and SEA 5) expressed the desired traits for water-limited conditions, which might be exploited in breeding efforts. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1007/s11104-012-1330-4 Authors Mura Jyostna Devi, Crop Science Department, North Carolina State University, Raleigh, NC, USA Thomas R. Sinclair, Crop Science Department, North Carolina State University, Raleigh, NC, USA Stephen E. Beebe, Centro Internacional de Agricultura Tropical (CIAT), A. A. 6713, Cali, Colombia Idupulapati M. Rao, Centro Internacional de Agricultura Tropical (CIAT), A. A. 6713, Cali, Colombia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and aims   The vertical distribution of available phosphorus (P) in the soil is usually heterogeneous with soil depth. However, little is known about the P efficiency of conifer species under vertically heterogeneous low-P conditions. The purpose of this study was to investigate the genetic variations in growth traits and P efficiency of Pinus massoniana , under heterogeneous and homogeneous low-P conditions. Methods   Pot experiments consisting of low-P (a low P level in all soil layers), layered-P (a high P level in the topsoil and a low P level in the bottom soil), and high-P (high P levels in all soil layers) conditions were designed and conducted. Three-way ANOVA was used to investigate genetic variations in P efficiency and the major growth traits under these three types of P conditions. Results   There were substantial genetic variations in the major growth traits, including tree height, stem diameter and seedling dry weight, under both heterogeneous and homogeneous low-P conditions. The heritability for major growth traits was high under both types of low-P condition. Moreover, there were significant genotype × P interaction effects for growth parameters. Conclusions   Our results indicate that it may be possible to select Masson pine genotypes with high P efficiency and productivity. The significant genotype × environment interactions should be exploited in breeding, and genotypes showing specific adaptations to certain nutrient environments should be bred and used within that environment. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1007/s11104-012-1352-y Authors Yi Zhang, Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Daqiao road, 73#, Fu Yang, Zhe Jiang, People’s Republic of China Zhichun Zhou, Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Daqiao road, 73#, Fu Yang, Zhe Jiang, People’s Republic of China Qing Yang, Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Daqiao road, 73#, Fu Yang, Zhe Jiang, People’s Republic of China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Purpose   This study investigated the residual contribution of legume and fertilizer nitrogen (N) to a subsequent crop under the effect of elevated carbon dioxide concentration ([CO 2 ]). Methods   Field pea ( Pisum sativum L.) was labeled in situ with 15 N (by absorption of a 15 N-labeled urea solution through cut tendrils) under ambient and elevated (700 μmol mol –1 ) [CO 2 ] in controlled environment glasshouse chambers. Barley ( Hordeum vulgare L.) and its soil were also labeled under the same conditions by addition of 15 N-enriched urea to the soil. Wheat ( Triticum aestivum L.) was subsequently grown to physiological maturity on the soil containing either 15 N-labeled field pea residues (including 15 N-labeled rhizodeposits) or 15 N-labeled barley plus fertilizer 15 N residues. Results   Elevated [CO 2 ] increased the total biomass of field pea (21 %) and N-fertilized barley (23 %), but did not significantly affect the biomass of unfertilized barley. Elevated [CO 2 ] increased the C:N ratio of residues of field pea (18 %) and N-fertilized barley (19 %), but had no significant effect on that of unfertilized barley. Elevated [CO 2 ] increased total biomass (11 %) and grain yield (40 %) of subsequent wheat crop regardless of rotation type in the first phase. Irrespective of [CO 2 ], the grain yield and total N uptake by wheat following field pea were 24 % and 11 %, respectively, higher than those of the wheat following N-fertilized barley. The residual N contribution from field pea to wheat was 20 % under ambient [CO 2 ], but dropped to 11 % under elevated [CO 2 ], while that from fertilizer did not differ significantly between ambient [CO 2 ] (4 %) and elevated [CO 2 ] (5 %). Conclusions   The relative value of legume derived N to subsequent cereals may be reduced under elevated [CO 2 ]. However, compared to N fertilizer application, legume incorporation will be more beneficial to grain yield and N supply to subsequent cereals under future (elevated [CO 2 ]) climates. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1007/s11104-012-1314-4 Authors Shu Kee Lam, Melbourne School of Land and Environment, The University of Melbourne, Victoria, 3010 Australia Deli Chen, Melbourne School of Land and Environment, The University of Melbourne, Victoria, 3010 Australia Rob Norton, Melbourne School of Land and Environment, The University of Melbourne, Victoria, 3010 Australia Roger Armstrong, Department of Primary Industries, Private Bag 260, Horsham, Victoria 3401, Australia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values. Methods   We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature. Results   Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yr −1 for Fagus sylvatica and 0.88 yr −1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yr −1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30 % higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula. Conclusions   We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting. Content Type Journal Article Category Review Article Pages 1-16 DOI 10.1007/s11104-012-1313-5 Authors I. Brunner, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, 8903 Birmensdorf, Switzerland M. R. Bakker, University of Bordeaux, UMR1220 TCEM, 33175 Gradignan, France R. G. Björk, Department of Biological and Environmental Sciences, University of Gothenburg, P.O. Box 461, 405 30 Gothenburg, Sweden Y. Hirano, Graduate School of Environmental Studies, Nagoya University, Nagoya, 464-8601 Japan M. Lukac, School of Agriculture, Policy and Development, University of Reading, Reading, RG6 6AR UK X. Aranda, Ecophysiology, IRTA Torre Marimon, 08140 Caldes de Montbui, Spain I. Børja, Norwegian Forest and Landscape Institute, P.O. Box 115, 1431 Ås, Norway T. D. Eldhuset, Norwegian Forest and Landscape Institute, P.O. Box 115, 1431 Ås, Norway H. S. Helmisaari, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland C. Jourdan, CIRAD, UMR Eco&Sols, 2, Place Pierre Viala, 34060 Montpellier, France B. Konôpka, Forest Research Institute, National Forest Centre, 96001 Zvolen, Slovak Republic B. C. López, CREAF Center for Ecological Research and Forestry Applications, and Ecology Unit of the Department of Plant and Animal Biology and Ecology, Edifici Ciències UAB, 08193 Bellaterra, Spain C. Miguel Pérez, Ecophysiology, IRTA Torre Marimon, 08140 Caldes de Montbui, Spain H. Persson, Department of Ecology, Swedish University of Agricultural Sciences SLU, P.O. Box 7044, 750 07 Uppsala, Sweden I. Ostonen, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Decreasing mineral concentrations in high-yield grains of the Green Revolution have coincided in time with rising global cardiovascular disease (CVD) mortality rates. Given the Magnesium (Mg) Hypothesis of CVD, it’s important to assess any changes in food crop Mg concentrations over the past 50+ years. Methods   Using current and historical published sources, Mg concentrations in “old” and “new” wheats, fruits and vegetables were listed/calculated (dry weight basis) and applied to reports of USA’s historic Mg supply, 1900–2006. Resulting trend in USA Mg supply was compared with USA trend in CVD mortality. Human Mg intake studies, old and new, were compared with the range of reported human Mg requirements. Results   Acknowledging assessment difficulties, since the 1850s, wheats have declined in Mg concentration 7–29 %; USA and English vegetables’ Mg declined 15–23 %, 1930s to 1980s. The nadir of USA food Mg supply in 1968 coincides with the USA peak in CVD mortality. As humans transition from “traditional” to modern processed food diets, Mg intake declines. Conclusions   Rising global CVD mortality may be linked to lower Mg intakes as world populations transition from traditional high Mg foods to those low in Mg due to declining crop Mg and processing losses. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1007/s11104-012-1471-5 Authors Andrea Rosanoff, Center for Magnesium Education & Research, LLC, 13-1255 Malama St., Pahoa, HI 96778, USA Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Aims   Metallothioneins are cysteine-rich, metal-binding proteins, but their exact functions are not fully understood. In this study, we isolated two metallothionein genes, BcMT1 and BcMT2 from Brassica campestris to increase our understanding of metal tolerance mechanisms in Brassica plants. Methods   Semi-quantitative RT-PCR was used to analyze expression of the two BcMTs genes. BcMT1 and BcMT2 were ectopically expressed in Arabidopsis thaliana . Quantitative real-time RT-PCR and GUS-staining method were used to select transgenic Arabidopsis plants. Cd and Cu concentrations were analyzed by flame atomic absorption spectrometry. Histochemical detection of H 2 O 2 and O 2 •− were conducted by 3,3-diaminobenzidine and nitroblue tetrazoliu-staining methods. Results   BcMT1 is expressed predominantly in roots, whereas BcMT2 is expressed mainly in leaves of B . campestris . Expression of BcMT1 was induced by both Cd and Cu, but expression of BcMT2 was enhanced only by Cd. Ectopic expression of BcMT1 and BcMT2 in Arabidopsis thaliana enhanced the tolerance to Cd and Cu and increased the Cu concentration in the shoots of the transgenic plants. Transgenic Arabidopsis accumulated less reactive oxygen species (ROS) than wild-type plants. Conclusions   BcMT1 and BcMT2 increased Cd and Cu tolerance in transgenic Arabidopsis , and decreased production of Cd- and Cu-induced ROS, thereby protecting plants from oxidative damage. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1486-y Authors Yanyan Lv, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China Xiaopeng Deng, Yunnan Academy of Tobacco Agricultural Sciences and China Tobacco Breeding Research (Southern) Center, Yuxi, 653100 China Lingtong Quan, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China Yan Xia, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China Zhenguo Shen, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X

Description: Background and Aims   Evidence shows that plants modify their microbial environment leading to the “crop rotation effect”, but little is known about the changes in rhizobacterial community structure and functionality associated with beneficial rotation effects. Methods   Polymerase chain reaction (PCR) and 454 GS FLX amplicon pyrosequencing were used to describe the composition of the rhizobacterial community evolving under the influence of pea, a growth promoting rotation crop, and the influence of three genotypes of chickpea, a plant known as an inferior rotation crop. The growth promoting properties of these rhizobacterial communities were tested on wheat in greenhouse assays. Results   The rhizobacterial communities selected by pea and the chickpea CDC Luna in 2008, a wet year, promoted durum wheat growth, but those selected by CDC Vanguard or CDC Frontier had no growth-promoting effect. In 2009, a dry year, the influence of plants was mitigated, indicated that moisture availability is a major driver of soil bacterial community dynamics. Conclusion   The effect of pulse crops on soil biological quality varies with the crop species and genotypes, and certain chickpea genotypes may induce positive rotation effects on wheat. The strength of a rotation effect on soil biological quality is modulated by the abundance of precipitation. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1007/s11104-012-1485-z Authors Chao Yang, Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, 1030, 1st Airport Road, Swift Current, SK, Canada S9H 3X2 Chantal Hamel, Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, 1030, 1st Airport Road, Swift Current, SK, Canada S9H 3X2 Yantai Gan, Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-Food Canada, 1030, 1st Airport Road, Swift Current, SK, Canada S9H 3X2 Vladimir Vujanovic, Department of Food & Bioproducts Sciences, University of Saskatchewan, Saskatoon, SK, Canada Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X