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  • Articles  (28)
  • Holocene  (9)
  • Nitrogen fixation  (9)
  • nitrogen  (9)
  • Crystal structure
  • Springer  (28)
  • 1995-1999  (28)
  • 1997  (28)
  • Geosciences  (28)
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  • Articles  (28)
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  • Springer  (28)
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  • 1995-1999  (28)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of soil treatment with cereal straw and method of crop establishment on field pea (Pisum sativum L.) N2 fixation (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 87-95 
    Details
    ISSN: 1432-0789
    Keywords: Crop rotation ; Field pea ; Mineral N ; Nitrogen fixation ; immobilisation ; Pisum sativum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha−1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by15N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha−1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha−1 (0–30 cm), and 5 or 10 t straw ha−1 reduced barley uptake of N by 10–38 kg N ha−1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420226
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  • 2
    Electronic Resource
    Electronic Resource
    Short- and long-term effects of ammonium on photodependent nitrogen fixation in wetland rice fields of Spain (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 353-357 
    Details
    ISSN: 1432-0789
    Keywords: Key words Acetylene reduction assay ; Anabaena sp. ; Ammonium ; Cyanobacteria ; Nitrogen fixation ; Wetland rice fields ; Nitrogenase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Short- and long-term experiments were conducted in the rice fields of Valencia, Spain, to determine the ecological significance of ammonium on nitrogen fixation. A significant inhibition of nitrogenase activity by ammonium, at concentrations higher than 0.5mM, was observed after 8h of incubation in short-term experiments done with a bloom of the N2-fixing cyanobacterium Anabaena sp. In a second set of short-term experiments for in situ assays of nitrogenase activity in the field, a significant correlation between nitrogenase activity and the number of N2-fixing cyanobacteria in soil was found. No significant inhibition of nitrogenase activity by ammonium at concentrations up to 2mM was observed in these assays after 24h of incubation. This lack of inhibition was probably due to the rapid decrease in ammonium content in the flood water. Only 5% of the ammonium initially added remained in the water 24h later. In the long-term experiments, nitrogenase activity was assayed in plots fertilized with 0, 70 and 140kgNha–1, over the cultivation cycle, for 5 years. A partial inhibition of nitrogenase activity by deep-placed N fertilizers was observed. Differences were only significant in 2 years. Mean results from 5 years only showed significant differences between plots fertilized with 0 and 140kgNha–1. The partial inhibition of nitrogenase activity by ammonium increased over the cultivation cycle. Inhibition was only significant in September, at the end of the cultivation cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050257
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  • 3
    Electronic Resource
    Electronic Resource
    Phenotypic grouping of Brazilian Bradyrhizobium strains which nodulate soybean (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 407-415 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsBradyrhizobium japonicum ; Bradyrhizobium elkanii ; Genetic variability ; Glycine max ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Several years of research have shown that there is a high genetic and physiological variability among Bradyrhizobium japonicum strains, culminating in a subdivision into two bacterial genotypes, and the description of the new species B. elkanii. In Brazil, large-scale soybean inoculation started in 1960 and today 15 million doses of inoculants are sold per year for an estimated area of 12 million ha. Efforts have been made to find strains able to fix high amounts of N2 under Brazilian soil conditions, but few laboratories cover basic studies on N2 fixation, such as strain classification into the two Bradyrhizobium species. In this study several characteristics of 40 soybean Bradyrhizobium strains, including 4 reference strains of B. japonicum (genotype I) species, 3 of B. elkanii (genotype II) and 1 of a mixed genotype were evaluated. The parameters analysed in vitro were: colony morphology, serological grouping, intrinsic resistance to antibiotics, synthesis of indole acetic acid, expression of hydrogenase activity and growth in a medium enriched with asparagine. In vivo, analyses performed included the nodulation of Rj 4 soybean cultivar Hill and the detection of symptoms caused by rhizobitoxine. These evaluations allowed a phenotypic grouping which positioned most of the strains utilized in Brazilian inoculants and studies, as well as some new strains isolated from the Cerrado region, within the species B. elkanii. However, environmental stresses and adaptation of Bradyrhizobium strains to the soil caused a large physiological and genetic variability in some isolates from the Cerrado soils in relation to the putative parental strain introduced 15 years ago, placing these isolates in an intermediate position between the two Bradyrhizobium species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050333
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  • 4
    Electronic Resource
    Electronic Resource
    Renodulation and characterization of Rhizobium isolates from cicer milkvetch (Astragalus cicer L.) (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 169-174 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsAstragalus cicer ; Nodulation ; DNA ; Milkvetch ; Nitrogen fixation ; Forage legume ; Rhizobium spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In 1993 and 1994, 12 bacterial isolates were isolated from root nodules of cicer milkvetch (Astragalus cicer). In the tests for nodulation of A. cicer by these bacterial isolates, five were found to form hypertrophic structures, while only two formed true nodules. These true nodules were formed in a sterilized soil system. This system might be able to act as a DNA donor to provide residual DNA to other microbes in the soil. The rhizobial isolates were thought to have lost genetic material crucial to nodulation during the isolation process. This hypothesis was supported by an experiment in which isolate B2 was able to nodulate A. cicer in vermiculite culture after being mixed with heat-killed rhizobia, Rhizobium leguminosarum bv. trifolii and R. loti. The nodulation would not occur in vermiculite culture system without the heat-killed rhizobia. Based on the biochemical data, the B2 and 9462L, which formed true nodules with A. cicer, were closely related. The rhizobia type cultures that nodulate A. cicer include Bradyrhizobium japonicum, Rhizobium leguminosarum bv. trifolii, R. leguminosarum bv. viceae, and R. loti. All of these rhizobia were from different cross-inoculation groups. The B2 and 9462L isolates could only nodulate Medicago sativa, Phaseolus vulgaris, and Melilotus officinalis, but not these species within the genus from which they were isolated: Astragalus. The traditional cross-inoculation group concept obviously does not fit well in the classification of rhizobia associated with Astragalus. The rhizobia isolated from A. cicer can be quite different, and the rhizobia able to renodulate A. cicer also quite diverse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050299
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  • 5
    Electronic Resource
    Electronic Resource
    Dual inoculation with strains of Bradyrhizobium japonicum and Azospirillum brasilense to improve growth and biological nitrogen fixation of soybean (Glycine max L.) (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 317-322 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soybean ; Isotope dilution ; Nitrogen fixation ; Bradyrhizobium japonicum ; Soil sterilization ; 15N ; Azospirillum brasilense ; Bacterial inoculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of inoculation with Bradyrhizobium japonicum and Azospirillum brasilense strains on the growth of soybean were evaluated with regard to the estimation of N2 fixation using the 15N isotope dilution technique. Inoculation, in general, increased the dry mass of soybean as well as nitrogen content. Dual inoculation with a mixture of B. japonicum and A. brasilense strains was superior over single inoculation with B. japonicum. Nitrogen fixed (Ndfa) varied according to inoculant and soil conditions. Percentages of nitrogen derived from air (% Ndfa) using a non-nodulating isoline were 72% and 76% for B. japonicum and B. japonicum plus A. brasilense, respectively, in non-sterile soil. A similar but higher trend was recorded in sterilized soil, in which the percentages of N2 fixed were 81% and 86% for single and dual inoculation, respectively. The correlation coefficient between N2 fixed and N uptake (r=0.94) and dry mass (r=0.89) was significant. Application of special bacterial inoculants in agricultural systems of Egypt seems to be a promising technology and could be used for improving soybean growth as well as soil fertility, thus minimizing environmental pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050250
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  • 6
    Electronic Resource
    Electronic Resource
    Management-induced change in labile soil organic matter under continuous corn in eastern Canadian soils (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 88-94 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass C ; Water-soluble organic carbon ; Light fraction organic carbon ; Fertilizer ; nitrogen ; 13C nuclear magnetic resonance ; Infrared spectrophotometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil samples taken from four experimental sites that had been cropped to continuous corn for 3–11 years in Ontario and Quebec were analyzed to evaluate changes in quantity and quality of labile soil organic carbon under different nitrogen (N) fertility and tillage treatments. Addition of fertilizer N above soil test recommendations tended to decrease amounts of water-soluble organic carbon (WSOC) and microbial biomass carbon (MBC). The quality of the WSOC was characterized by 13C nuclear magnetic resonance and infrared spectrophotometry and the results indicated that carbohydrates, long-chain aliphatics and proteins were the major components of all extracts. Similar types of C were present in all of the soils, but an influence of management was evident. The quantity of soil MBC was positively related to the quantities of WSOC, carbohydrate C, and organic C, and negatively related to quantities of long-chain aliphatic C in the soil. The quantity of WSOC was positively related to the quantities of protein C, carbohydrate C, and negatively related to the quantity of carboxylic C. The quantity of soil MBC was not only related to quantities of soil WSOC but also to the quality of soil WSOC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050348
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  • 7
    Electronic Resource
    Electronic Resource
    Survival and symbiotic properties of Bradyrhizobium japonicum in the presence of thiram: isolation of fungicide resistant strains (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 141-145 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsBradyrhizobium japonicum ; Nodulation ; Nitrogen fixation ; Soybean ; Thiram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The fungicide thiram, widely used as a chemical seed protectant, induces a strong inhibition of primary nodulation in the crown zone of soybean roots. The present work reports on the isolation of Bradyrhizobium japonicum strains resistant to thiram, some of which (T3B, A86 and A2) maintained their capacity for nodulation and were still efficient symbionts, but some (A1, C1 and C6) lost the ability to stimulate nodulation. Characterization tests such as growth at different pH, denitrifying ability, salt tolerance, production of siderophores and phosphate solubilization were performed on the resistant strains. Inoculants produced from these strains could be appropriate for use with thiram-treated seeds, without causing a loss of bacteria viability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050357
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  • 8
    Electronic Resource
    Electronic Resource
    Natural abundance of 15N in sweet potato, pumpkin, sorghum and castor bean: possible input of N2-derived nitrogen in sweet potato (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 152-154 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsCucurbita moschata ; Ipomoea batatas ; Nitrogen fixation ; δ15N method ; Sorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two combinations of plant species, sweet potato (three cultivars) and pumpkin, and sweet sorghum (three cultivars) and castor bean were grown separately in three plots of alluvial soil from June to September 1996. The shoots (leaves plus stems) of sweet potato and pumpkin, and the whole tops (leaves plus stems and grains) of sweet sorghum and castor bean were harvested twice, once in August and once in September in order to analyze their natural abundance of 15N (δ15N). The δ15N values of two of the varieties of sweet potato harvested in September were significantly lower than those of pumpkin, while δ15N values of sweet potato and pumpkin harvested in August, as well as those of sweet sorghum and castor bean harvested in August and September, did not significantly differ. The lower δ15N values observed in the September-harvested sweet potato may indicate that as much as 40% of the N intake of this species is derived from dinitrogen. This species is known to have a high ability to take up N from undefined sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050359
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  • 9
    Electronic Resource
    Electronic Resource
    Microbial contribution to extractable N and P after air-drying of dry tropical soils (1997)
    Springer
    Biology and fertility of soils 26 (1997), S. 31-34 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Air-drying ; Extractable ; nitrogen ; Extractable phosphorus ; Tropical soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The microbial contribution to extractable N and P after the air-drying of eight Indian dry tropical Ultisols was quantified. Air-drying of the soils decreased microbial biomass C by 25–53% but increased extractable N and P by 14–34% and 24–121%, respectively. This increase in the extractable N and P was accounted for, to some extent, by microbial biomass killed due to air-drying. Microbial biomass contributes 17–36% and 19–82% to the extractable N and P, respectively, possibly due to air-drying of the soils. I conclude that due to contamination of microbial biomass with the available nutrients in air-dried soils, measurements of extractable nutrients should be made on field-moist soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050339
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  • 10
    Electronic Resource
    Electronic Resource
    Nodulation of African yam bean (Sphenostylis stenocarpa) by Bradyrhizobium sp. isolated from Erythrina brucei (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 209-210 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsBradyrhizobium ; Sphenostylis stenocarpa ; Nitrogen fixation ; Soil reclamation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract African yam bean (Sphenostylis stenocarpa), which is widely cultivated in Africa because of its growth capability on marginal soils, was nodulated by an endosymbiont (characterized and designed Bradyrhizobium sp. AUEB20) isolated from the Ethiopian tree Erythrina brucei with the formation of a small number of large, indeterminate N2-fixing nodules. In contrast, 24 other isolates from Ethiopian woody legumes were ineffective. Strain AUEB20 promiscuously nodulated a number of tropical legumes, but none out of five European crop plants tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050305
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  • 11
    Electronic Resource
    Electronic Resource
    Diversity, adaptation and activity of the bacterial flora in saline environments (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 211-223 
    Details
    ISSN: 1432-0789
    Keywords: Key words Bacterial flora ; Salt-affected soils ; Salt marshes ; Osmotic adjustment ; Microbial activity ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Saline environments have a natural bacterial flora, which may play a significant role in the economy of these habitats. The natural saline environments (usually containing salinity equivalent to 4–30% NaCl) are aquatic (e.g. salt marshes) or terrestrial (e.g. saline lands). Saline environments include an increasing area of salt-affected cultivated soils throughout the world. These environments contain various ions which may interfere with uptake of water and which may be toxic to a large number of organisms. Saline environments harbour taxonomically diverse bacterial groups, which exhibit modified physiological and structural characteristics under the prevailing saline conditions. The majority of these bacteria can osmoregulate by synthesizing specific compatible organic osmolytes such as glutamine, proline and glycine betaine and a few of them accumulate inorganic solutes such as Na+, K+ and Mg2+. The morphology of the bacteria is usually modified, cells are usually elongated, swollen and showing shrinkage, in addition to changes in the cell and cytoplasmic volume. The chemical composition of membranes may also occasionally be modified, and the synthesis pattern of proteins, lipids, fatty acids and polysaccharides may change with a moderate increase in salinity. However, ultrastructural alterations in cells of halophilic bacteria have not been reported, and profound changes in cellular properties of these bacteria only occur at concentrations above 2MNaCl. Evidence has accumulated that the bacteria are essential elements in the saline environment because of their activity such as degradation of plant remains, nitrogen fixation and production of active metabolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050306
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  • 12
    Electronic Resource
    Electronic Resource
    The volcanic history of Ruapehu during the past 2 millennia based on the record of Tufa Trig tephras (1997)
    Springer
    Bulletin of volcanology 59 (1997), S. 136-146 
    Details
    ISSN: 1432-0819
    Keywords: Key words Ruapehu ; Tufa Trig Formation ; Holocene ; Tephra ; Hydrovolcanic ; Pyroclast morphology ; Crater Lake ; Marker beds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Tufa Trig Formation comprises a sequence of at least 19 andesitic tephras erupted from Mt. Ruapehu (Tongariro Volcanic Centre, New Zealand). Tephras of Tufa Trig Formation are the most recent eruptives from Ruapehu, dated between ca. 1850 years B.P. and the present. Members of the Formation show restricted dispersals, principally to the east of Mt. Ruapehu. Volumes calculated for the most widespread members are all less than 0.1 km3. Compared with other Mt. Ruapehu eruptives, Tufa Trig Formation tephras represent small eruptions that have contributed little tephra to the ring plain. They do, however, show a greater frequency of eruption with one event occurring on average every 100 years. Tufa Trig Formation members Tf3–Tf18 are black to dark grey, vitric, coarse-ash and lapilli-grade tephras which mantle the relief. They contain juvenile vitric particles which exhibit varying degrees of vesicularity, together with free crystals of pyroxene and feldspar, and few lithic fragments. Several morphological types of vitric pyroclasts are recognised in these tephras, the dominant type being of equant blocky morphology with fracture-bound surfaces (type-1 morphology). Field characteristics, tephra distributions, and the morphologies and textures of constituent pyroclasts suggest that these members (Tf3–Tf18) are the products of small-volume hydrovolcanic eruptions resulting from the interaction of fresh magma and meteoric water. We propose that a source of this water was an ancestral crater lake which formed within the late Holocene ca. 3000 years B.P. The morphological, compositional, and chemical (major-element) characteristics of three Tufa Trig Formation Tephras are compared with those of two new tephras erupted from Ruapehu Volcano during the October 1995 eruptions which comprise part of a newly defined member (Tf19) of Tufa Trig Formation. The comparisons support our interpretation that the majority of the Tufa Trig Formation tephras are primarily the products of hydrovolcanic eruptions. Other members of the Formation (Tf1 and Tf2) are coarse-grained scoriaceous tephras and are interpreted to be the products of strombolian events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050181
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  • 13
    Electronic Resource
    Electronic Resource
    Multi-component carbon isotope evidence of early Holocene environmental change and carbon-flow pathways from a hard-water lake in northern Sweden (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 219-233 
    Details
    ISSN: 1573-0417
    Keywords: northern Sweden ; stable carbon isotopes ; carbon isotope fractionation ; limnic sediments ; Holocene ; lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A 9000-year carbonate-rich sediment sequence from a small hard-water lake in northernmost Sweden was studied by means of multi-component stable carbon isotope analysis. Radiocarbon dating of different sediment fractions provides chronologic control and reveals a rather constant hard-water effect through time, suggesting that the lake has remained hydrologically open throughout the Holocene. Successive depletion of 13C in fine-grained calcite and carbonate shells during the early Holocene correlate with a change in catchment vegetation from pioneer herb communities to boreal forest. The vegetational change and associated soil development likely gave rise to an increased supply of 13C-depleted carbon dioxide in groundwater recharging the lake. This process is therefore believed to be the main cause of decreasing values of δ13C in dissolved inorganic carbon of the lake and thereby in limnic carbonates. Strongly 13C-depleted sedimentary organic matter may be related to enhanced kinetic fractionation during photosynthetic assimilation by means of proton pumping in Characean algae. This interpretation is supported by a substantial offset between δ13C of DIC as recorded by mollusc shells and δ13C of fine-grained calcite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007953614927
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  • 14
    Electronic Resource
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    Holocene history of lacustrine and marsh sediments in a dune-blocked drainage, Southwestern Nebraska Sand Hills, U.S.A. (1997)
    Springer
    Journal of paleolimnology 17 (1997), S. 67-83 
    Details
    ISSN: 1573-0417
    Keywords: paleohydrology ; paleoclimate ; sand dunes ; eolian ; Holocene ; Nebraska
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract As many as 2500 interdune lakes lie within the Nebraska Sand Hills, a 50 000 km stabilized sand sea. The few published data on cores from these lakes indicate they are typically underlain by less than two m of Holocene lacustrine sediments. However, three lakes in the southwestern Sand Hills, Swan, Blue, and Crescent, contain anomalously thick marsh (peat) and lacustrine (gyttja) sediments. Swan Lake basin contains as much as 8 m of peat, which was deposited between about 9000 and 3300 years ago. This peat is conformably overlain by as much as 10.5 m of gyttja. The sediment record in Blue lake, which is 3 km downgradient from Swan lake, dates back to only about 6000 years ago. Less than two m of peat, which was deposited from 6000 to 5000 years ago, is overlain by 12 m of gyttja deposited in the last 4300 years. Crescent Lake basin, one km downgradient from Blue Lake, has a similar sediment history except for a lack of known peat deposits. Recently, a 8-km long segment of a paleovalley was documented running beneath the three lakes and connecting to the head of Blue Creek Valley. Blockage of this paleovalley by dune sand during two arid intervals, one shortly before 10 500 yr BP and one in the mid-Holocene, has resulted in a 25 m rise in the regional water table. This made possible the deposition of organic-rich sediment in all three lakes. Although these lakes, especially Swan, would seem ideal places to look for a nearly complete record of Holocene climatic fluctuations, the paleoclimatic record is confounded by the effect dune dams have on the water table. In Swan Lake, the abrupt conversion from marsh to lacustrine deposition 3300 years ago does not simply record the change to a wetter regional climate; it reflects the complex local hydrologic changes surrounding the emplacement and sealing of dune dams, as well as regional climate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007917110965
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  • 15
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    The plant-macrofossil record of past lake-level changes (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 15-28 
    Details
    ISSN: 1573-0417
    Keywords: plant-macrofossils ; palaeoecology ; water-chemistry ; trophic-status ; water-depth ; lake-level changes ; Holocene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Plant-macrofossil analysis is one of the most useful biostratigraphical methods for the reconstruction of former lake-level changes. The distribution of submerged, floating-leaved and emergent lake-shore vegetation is mainly dependant on water depth, but water chemistry and nutrient status must also be taken into account when interpreting water-level changes. Lake-level studies should be based on the investigation of several littoral cores along a transect perpendicular to the lake-shore. Multiple cores are essential for separating genuine lake-level changes from other processes influencing the plant-macrofossil record. Physical analyses of sediment stratigraphy provide important additional information to the plant-fossil record, because natural infilling processes and erosion from the catchment must be distinguished from climatic events causing a change in the water level. Here we review several important concepts, including suitability of lakes for lake-level study, the degree of detail required in the analysis, and macrofossil records of lake-level changes, and illustrate those concepts by examples from southern Sweden and Minnesota. We discuss how to reconcile alternative hypotheses for the stratigraphic changes seen in the macrofossil assemblages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007958511729
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  • 16
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    The relationship between glacial activity and sediment production: evidence from a 4450-year varve record of neoglacial sedimentation in Hector Lake, Alberta, Canada (1997)
    Springer
    Journal of paleolimnology 17 (1997), S. 319-330 
    Details
    ISSN: 1573-0417
    Keywords: varves ; glacial history ; Canadian Rocky Mountains ; Holocene ; Neoglaciation ; glaciolacustrine sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract A 4450-year sequence of varves, spanning the entire Neoglacialinterval, has been recovered from Hector Lake, Alberta. The varve record is compared to records of regional glacial history toevaluate therelationship between alpine glacial activity and sediment production. Glacial controls on sediment production vary with the timescale considered. Long-term variations in sedimentation rate, of centuries to millennial duration, reflect changes in ice extent of the same timescale. Superimposed on these long-term changes is decadal-scale variability that is complexly related to upvalley ice extent. Over the short term, high sedimentation rates may be associated with glacier maximum stands, or with periods of glacier advance or recession. Overthe last millennium at least, highest sedimentation rates appear to have been associated with transitional periods, preceding or post-dating maximum ice stands, rather than with times of maximum ice extent.
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    URL: http://dx.doi.org/10.1023/A:1007948327654
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    A Holocene paleosalinity diatom record from southwestern Saskatchewan, Canada: Harris Lake revisited (1997)
    Springer
    Journal of paleolimnology 17 (1997), S. 23-31 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; salinity ; climatic change ; Holocene ; CypressHills ; Saskatchewan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Fossil diatoms were analysed from a 10.3 m core from Harris Lake, Cypress Hills, Saskatchewan, and a diatom-salinity transfer function was used to construct a history of Holocene salinity changes for the lake. The diatom paleosalinity record indicates that Harris Lake remained fresh 〈0.5 g l-1 throughout the Holocene, with only slight increases in salinity between approximately 6500 and 5200 years BP. This interval corresponds to the only period in the lake's history when planktonic diatoms were abundant; benthic Fragilaria taxa, mainly F. pinnata, F. construens and F. brevistriata were dominant throughout most of the Holocene. The shift from a benthic to a planktonic diatom flora between 6500 and 5200 years BP may be an indirect response to a warmer climate that reduced forest cover in the watershed and allowed greater rates of inorganic sedimentation. The small salinity increase that accompanies the floristic change is probably not the result of lower lake levels; in fact the lake was probably deeper at this point than in the later Holocene. This paleosalinity record indicates that Harris Lake did not experience episodes of hypersalinity during the mid-Holocene, as suggested by a previous study, and that the lake may have been fresh during the early Holocene as well.
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    URL: http://dx.doi.org/10.1023/A:1007956808240
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  • 18
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    The effect of Holocene treeline fluctuations on the sediment chemistry of Lake Kilpisjärvi, Finland (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 145-163 
    Details
    ISSN: 1573-0417
    Keywords: Holocene ; Finland ; lake sedimentchemistry ; treeline ; pollen diagram ; erosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The sediments of Lake Kilpisjärvi were described and analysed for element chemistry and pollen to study the effects of treeline fluctuations in the catchment. Lake Kilpisjärvi is one of the largest lakes in Finnish Lapland, with its catchment partly above the treeline and partly covered with mountain birch woodland. Although the presence of subfossil pine shows that the catchment was previously covered with mountain birch woodland during the Holocene, the present pine treeline has receded 70 km from the lake. Pollen analysis results show that pine immigrated to the area during the Atlantic chrone and that ∼7000 BP pine forests occupied much of the catchment. Pine started to decline around 3500 BP and vegetation in the catchment became more open. Alkaline and alkaline earth metals and some transition metals document the change from glaciolacustrine clay to more organic sediment. However, these geochemical trends give no indication of changes in erosion rate resulting from changes in catchment vegetation. These changes were detected by plotting suitable element ratios. In addition to the conventional Si/Al and Na/K ratios, the Ca labile /Si ratio and especially the ratio of labile Ca to K were found to be useful. Of all the elements analysed, potassium showed the strongest reaction to changes in the balance between weathering and erosion. During the phase of denser forests, chemical weathering was dominant, whereas during phases of open catchment, physical erosion prevailed. The effects of changing climate and catchment vegetation were distinguished from other signals. For instance, iron and manganese were enriched at the top of the core due to diffusion and, at the same time, old precipitate layers persisted after burial to deeper levels in the sediment. These iron and manganese rich layers had an effect on the distributions of cobalt, zinc, and vanadium, showing increased concentrations of these elements. Other effects that made the interpretation of chemical records difficult were the effect of ongoing mineralization of organic matter in the top layers of sediment and the effect of biogenic silicon. Owing to the stable conditions of the lake, the desired chemical signals were detected, despite the masking trends.
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    URL: http://dx.doi.org/10.1023/A:1007978318562
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  • 19
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    SOLAR ACTIVITY VARIATIONS RECORDED IN VARVED SEDIMENTS FROM THE CRATER LAKE OF HOLZMAAR – A MAAR LAKE IN THE WESTEIFEL VOLCANIC FIELD, GERMANY (1997)
    Springer
    Surveys in geophysics 18 (1997), S. 163-182 
    Details
    ISSN: 1573-0956
    Keywords: Eifel ; Germany ; Holocene ; lacustrine sediments ; solar forcing ; varves ; Weichselian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Annually laminated sediments from Lake Holzmaar (Germany) provide high resolution sedimentological and palaeoenvironmental data of the last 22,500 years. Weichselian periglacial varves and Holocene organic varves indicate different depositional environments. For the best preserved sections from both parts, spectral analyses were performed in order to detect cyclic fluctuations in varve thickness. Weichselian varves are dominated by an 88 year periodicity. Linear spectral analysis of Holocene varves provides no significant cyclicity. But, supposing nonlinear transformations of the solar signal through the Lake Holzmaar ecosystem during the Holocene, an adequate nonlinear spectral analysis method was able to detect periodicities of 11, 88, and 208 years. The existence of these cyclicities, comparable to the solar activity fluctuations, give further evidence for the existence of a sun-climate relationship, based on a not yet completely understood mechanism.
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    URL: http://dx.doi.org/10.1023/A:1006531825130
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  • 20
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    Structure of Cu-bearing orthopyroxene, Mg(Cu.56,Mg.44)Si2O6, and behavior of Cu2+ in the orthopyroxene structure (1997)
    Springer
    Physics and chemistry of minerals 24 (1997), S. 463-476 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cu2+-beearing orthopyroxene ; Orthopyroxene ; Crystal structure ; Jahn-Teller effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Cu-bearing pyroxene, Mg(Cu.56,Mg.44)Si2O6, has been synthesized by a flux method and crystal structure refinement has been performed by single crystal X-ray diffraction. It is found that the crystal structure is orthorhombic (space group Pbca) with unit cell dimensions of a=18.221(4), b=8.890(1), c=5.2260(7)Å and the cell volume of 846.5( )3Å3. In the M2-site one of the M-O bonds(M-O3B) is extremely expanded from 2.444(2) in enstatite to 2.732(2), thus the coordination polyhedron around M2-site is regarded as square pyramidal rather than square planar or octahedral. It is also found that the M1-site in the pyroxene structure is occupied almost exclusively by Mg, while the M2-site is almost evenly occupied by Mg and Cu. The observed extreme site preference shown by Cu2+ is unusual among the divalent cations with similar ionic sizes.
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    URL: http://dx.doi.org/10.1007/s002690050061
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  • 21
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    Ammonia volatilization from a seasonally and spatially variable grazed grassland: Yellowstone National Park (1997)
    Springer
    Biogeochemistry 36 (1997), S. 189-203 
    Details
    ISSN: 1573-515X
    Keywords: ammonia volatilization ; grassland ; nitrogen ; ungulate ; Yellowstone National Park
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured ammonia volatilization at three topographic positions(hilltop, mid-slope, slope-bottom) on three grassland landscapes at threetimes during 1995 (April, May, July) on the northern winter range ofYellowstone National Park that supports large herds of native ungulates.Percent ammonia-N lost from all sites during the study ranged 1–24%of urea-N applied. Volatilization among sites was negatively related tosoil cation-exchange capacity (r = –0.85) and rates were highest inJuly. We used the relationship between soil CEC and percent Nvolatilized from urea-amended plots to estimate annual ammonia-Nvolatilization from 5 sites for which annual ungulate urine inputs werepreviously determined (Frank et al. 1994). Estimated mean annualammonia-N volatilized from those sites was 1.4 kg/ha/yr, which wasless than a previously reported regional atmospheric deposition rate (2kg/ha/yr; Swank 1984). Results indicate the need to understand theinteraction between (1) spatially heterogeneous patterns of soilprocesses, and 2) nonuniform patterns of ungulate use of landscapes todetermine rates of ecosystem-level N-gaseous loss. Findings alsosuggest that ammonia-N volatilized from urine patches should not leadto a decline in soil N in this ecosystem.
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    URL: http://dx.doi.org/10.1023/A:1005705121160
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    Marine nitrogen: Phosphorus stoichiometry and the global N:P cycle (1997)
    Springer
    Biogeochemistry 37 (1997), S. 237-252 
    Details
    ISSN: 1573-515X
    Keywords: freshwater ; limitation ; marine ; nitrogen ; phosphorus ; ratio ; stoichiometry ; trace elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen supply is often assumed to limitmarine primary production. A global analysis of totalnitrogen (N) to phosphorus (P) molar ratios shows thattotal N:P is low (〈16:1) in some estuarine andcoastal ecosystems, but up to 100:1 in open oceans.This implies that elements other than N may limitmarine production, except in human impacted, estuarineor coastal ecosystems. This pattern may reconcileconflicting enrichment studies, because N additionfrequently increases phytoplankton growth where totalN:P is expected to be low, but P, Fe, or Si augmentphytoplankton growth in waters where total N:P ishigh. Comparison of total N:P stoichiometry betweenmarine and freshwaters yields a model of the form ofthe aquatic N:P cycle.
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    URL: http://dx.doi.org/10.1023/A:1005712322036
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    Concentrations and controls of dissolved organic matter in a constricted-channel region of the Ohio River (1997)
    Springer
    Biogeochemistry 38 (1997), S. 41-65 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; nitrogen ; Ohio River ; phosphorus ; Red field ratios ; dissolved organic matter ; rivers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A 12-month study was conducted to measure the concentrations ofdissolved organic matter (DOC, TDN, TDP) in four sites within a119 km long reach of the Ohio River, near Louisville, KY. In thisstudy we test whether specific geomorphological and biologicalfactors influenced variations in dissolved organic matter.Concentrations of DOC in the river averaged ≈1200μmol/L, and varied by nearly two orders of magnitudeseasonally (mean DOC during base flow ≈620 μmol/L).Peak periods for DOC at all sites were during April–May. Thesite nearest a navigation dam (deeper, lower current velocities)had significantly lower concentrations of TDN and greater C:Nratios than upstream sites. The largest tributary entering thisreach (Kentucky River) had no significant effect on levels of DOMin the main river, despite having significantly greaterconcentrations of TDN and lower levels of DOC during most monthsof the year. Concentrations of DOC, TDN, and TDP were notsignificantly different in littoral and pelagic habitats at allsites studied, suggesting little floodplain influence on DOM inthis constricted-channel section of the Ohio River. C:N ratios ofDOM in the Ohio were significantly different among seasons; C:Nexceeded or equaled Redfield ratios in summer and fall (6 to 10),but were below Redfield (1.8 to 3.0) during winter and spring.Regression models suggest that total phytoplankton densities andflow conditions are the two most important factors regulating DOMin this very large river.
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    URL: http://dx.doi.org/10.1023/A:1005708326368
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  • 24
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    Solute dynamics in soil water and groundwater in a central Amazon catchment undergoing deforestation (1997)
    Springer
    Biogeochemistry 38 (1997), S. 303-335 
    Details
    ISSN: 1573-515X
    Keywords: Amazon ; deforestation ; hydrologic pathway ; groundwater ; nitrogen ; rain forest ; slash-and-burn agriculture ; solutes ; tropical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Hydrochemical changes caused by slash-and-burnagricultural practices in a small upland catchment inthe central Amazon were measured. Soluteconcentrations were analyzed in wet deposition,overland flow, shallow throughflow, groundwater andbank seepage in a forested plot (about 5 ha) and anadjacent plot (about 2 ha) which had been deforestedin July 1989 and planted to manioc, and in streamwater in partially deforested and forested catchments. Measurements were made from November 1988 to June1990. The effects of slash-and-burn agriculturalpractices observed in the experimental plot includedincreased overland flow, erosion, and large losses ofsolutes from the rooted zone. Concentrations ofNO3 -, Na+, K+, SO4 2-,Cl- and Mn in throughflow of the experimentalplot were higher than those of the control plot bymore than a factor of 10. Extensive leaching occurredafter cutting and burning, but solute transfers werediminished along pathway stages of throughflow togroundwater, and particularly within the riparian zoneof the catchment. High concentrations of N and P inoverland flow indicate the importance of usingforested riparian buffers to mitigate solute inputs toreceiving waters in tropical catchments.
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    URL: http://dx.doi.org/10.1023/A:1005801303639
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  • 25
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    Nutrient limitation and soil development: Experimental test of a biogeochemical theory (1997)
    Springer
    Biogeochemistry 37 (1997), S. 63-75 
    Details
    ISSN: 1573-515X
    Keywords: nutrient limitation ; soil development ; nitrogen ; phosphorus ; chronosequence ; Hawai'i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Walker & Syers (1976) proposed a conceptual model that describesthe pattern and regulation of soil nutrient pools and availability during long-term soil and ecosystem development. Their model implies that plantproduction generally should be limited by N on young soils and by P on oldsoils; N and P supply should more or less equilibrate onintermediate-aged soils. We tested the application of this model to nutrientlimitation, using a well characterized substrate age sequence in Hawaiianmontane rain forest. Earlier experiments had evaluated nutrient limitationin forests on a young (300 y) and an old (4,100,000 y) substrate on the samedevelopmental sequence; N alone limited tree growth on the youngsubstrate, while P alone did so on the old one. An additional fertilizerexperiment based on replicated treatments with N, P, and all othernutrients combined, applied in individually and in all factorialcombinations, was established in an intermediate-aged site in theLaupahoehoe Forest Reserve, Hawaii. Here, diameter increments of thedominant tree Metrosideros polymorpha increased slightly with Nadditions, and nearly doubled when N and P were added together.Additions of elements other than N and P had no significant effecton growth. These results show that N and P had equilibrated (relativeto plant requirements) in the intermediate aged site. Together withthe earlier experiments, these results suggest that the Walker and Syersmodel provides a useful starting point for explaining the nature anddistribution of nutrient limitation in forest ecosystems.
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    URL: http://dx.doi.org/10.1023/A:1005757218475
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    The effects of ammonium sulphate deposition and root sinks on soil solution chemistry in coniferous forest soils (1997)
    Springer
    Biogeochemistry 38 (1997), S. 255-280 
    Details
    ISSN: 1573-515X
    Keywords: aluminium ; forest soils ; lysimeters ; nitrification ; nitrogen ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The effects of enhanced (NH4 2SO4deposition on soil solution cation and anion concentrations and annualionic fluxes were followed using a standardised experimental protocolin six European coniferous forests with contrasting soil types, pollutioninputs and climate. Native soil cores containing a ceramic suction cupwere installed in the field, roofed and watered every two weeks withlocal throughfall or local throughfall with added(NH4)2SO4 at 75 kgNH4 +-N ha-1 a-1. Livingroot systems were established in half of the lysimeters.Untreated throughfall NH4 +-N deposition at thesites ranged from 3.7 to 29 kg ha-1 a-1Soil leachates were collected at two weekly intervalsover 12 months and analysed for volume, andconcentrations of major anions and cations. Increasesin soil solution NO3 - concentrations inresponse to N additions were observed after 4–9months at three sites, whilst one sandy soil with highC:N ratio failed to nitrify under any of thetreatments. Changes in NO3 - concentrationsin soil solution controlled soil solution cationconcentrations in the five nitrifying soils, withAl3+ being the dominant cation in the more acidsoils with low base saturation. The acidification responses ofthe soils to the (NH4 2SO4additions were primarily related to the ability of thesoils to nitrify the added NH4 +. pH and soiltexture seemed important in controllingNH4 + leaching in response to the treatments,with two less acidic, clay/clay loam sites showingalmost total retention of added NH4 +, whilstnearly 75% of the added N was leached asNH4 + at the acid sandy soils. The presenceof living roots significantly reduced soil solutionNO3 - and associated cation concentrations attwo of the six sites. The very different responses of the sixsoils to increased (NH4)2SO4deposition emphasise that the establishment of N critical loadsfor forest soils need to allow for differences in N storagecapacity and nitrification potential.
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    URL: http://dx.doi.org/10.1023/A:1005875505591
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    Background concentration of 226Ra in terrestrial animals (1997)
    Springer
    Biogeochemistry 39 (1997), S. 1-13 
    Details
    ISSN: 1573-515X
    Keywords: 226Ra accumulation ; background level ; natural zones ; terrestrial animals ; nitrogen ; rain forest ; slash-and-burn agriculture ; solutes ; tropical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Radium (226Ra) accumulation by terrestrial animalswas studied in the territory of the former USSR. Concentrations of226Ra in different soils, plants and animals aresimilar to the background level. For soils it fluctuates in range0.5–1.5 × 10-12 gg-1 (18.3–55 Bq/kg), for plantsbetween 0.1–1.7 × 10-12 gg-1 (3.7–62.1 Bq/kg), and for animals– 0.02–1.5 ×10-12 g g-1(0.73–55 Bq/kg). There were no significant differences in226Ra concentration between animals of different groups. Themaximal 226Ra concentration is marked for the woodlouse Hemilepistus aphganicus from the Badkhyz reserve in Turkmenistan– 1.49 × 10-12g g-1 of dwt (54.4 Bq/kg), the minimal one– for Colorado beetle Leptinotarsadecemlineata from the vicinity of Moscow – 0.02× 10-12 gg-1 of dwt (0.73 Bq/kg). Concentration ratios for linkssoil – plant, plant – animal andprey – carnivore are usually close to 1. A hypothesison the similarity of 226Raconcentration in different animals is discussed.
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    URL: http://dx.doi.org/10.1023/A:1005857427940
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  • 28
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    Climate: Is the past the key to the future? (1997)
    Springer
    Geologische Rundschau 86 (1997), S. 471-491 
    Details
    ISSN: 0016-7835
    Keywords: Key words Climate change ; Paleoclimatology ; Cretaceous ; Holocene ; Quaternary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The climate of the Holocene is not well suited to be the baseline for the climate of the planet. It is an interglacial, a state typical of only 10% of the past few million years. It is a time of relative sea-level stability after a rapid 130-m rise from the lowstand during the last glacial maximum. Physical geologic processes are operating at unusual rates and much of the geochemical system is not in a steady state. During most of the Phanerozoic there have been no continental ice sheets on the earth, and the planet’s meridional temperature gradient has been much less than it is presently. Major factors influencing climate are insolation, greenhouse gases, paleogeography, and vegetation; the first two are discussed in this paper. Changes in the earth’s orbital parameters affect the amount of radiation received from the sun at different latitudes over the course of the year. During the last climate cycle, the waxing and waning of the northern hemisphere continental ice sheets closely followed the changes in summer insolation at the latitude of the northern hemisphere polar circle. The overall intensity of insolation in the northern hemisphere is governed by the precession of the earth’s axis of rotation, and the precession and ellipticity of the earth’s orbit. At the polar circle a meridional minimum of summer insolation becomes alternately more and less pronounced as the obliquity of the earth’s axis of rotation changes. Feedback processes amplify the insolation signal. Greenhouse gases (H2O, CO2, CH4, CFCs) modulate the insolation-driven climate. The atmospheric content of CO2 during the last glacial maximum was approximately 30% less than during the present interglacial. A variety of possible causes for this change have been postulated. The present burning of fossil fuels, deforestation, and cement manufacture since the beginning of the industrial revolution have added CO2 to the atmosphere when its content due to glacial-interglacial variation was already at a maximum. Anthropogenic activity has increased the CO2 content of the atmosphere to 130% of its previous Holocene level, probably higher than at any time during the past few million years. During the Late Cretaceous the atmospheric CO2 content was probably about four times that of the present, the level to which it may rise at the end of the next century. The results of a Campanian (80 Ma) climate simulation suggest that the positive feedback between CO2 and another important greenhouse gas, H2O, raised the earth’s temperature to a level where latent heat transport became much more significant than it is presently, and operated efficiently at all latitudes. Atmospheric high- and low-pressure systems were as much the result of variations in the vapor content of the air as of temperature differences. In our present state of knowledge, future climate change is unpredictable because by adding CO2 to the atmosphere we are forcing the climate toward a “greenhouse” mode when it is accustomed to moving between the glacial–interglacial “icehouse” states that reflect the waxing and waning of ice sheets. At the same time we are replacing freely transpiring C3 plants with water-conserving C4 plants, producing a global vegetation complex that has no past analog. The past climates of the earth cannot be used as a direct guide to what may occur in the future. To understand what may happen in the future we must learn about the first principles of physics and chemistry related to the earth’s system. The fundamental mechanisms of the climate system are best explored in simulations of the earth’s ancient extreme climates.
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    URL: http://dx.doi.org/10.1007/s005310050155
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