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  • 1
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    Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment (2010)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2010-10-29
    Description: Biodiversity is rapidly declining, and this may negatively affect ecosystem processes, including economically important ecosystem services. Previous studies have shown that biodiversity has positive effects on organisms and processes across trophic levels. However, only a few studies have so far incorporated an explicit food-web perspective. In an eight-year biodiversity experiment, we studied an unprecedented range of above- and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Scherber, Christoph -- Eisenhauer, Nico -- Weisser, Wolfgang W -- Schmid, Bernhard -- Voigt, Winfried -- Fischer, Markus -- Schulze, Ernst-Detlef -- Roscher, Christiane -- Weigelt, Alexandra -- Allan, Eric -- Bessler, Holger -- Bonkowski, Michael -- Buchmann, Nina -- Buscot, Francois -- Clement, Lars W -- Ebeling, Anne -- Engels, Christof -- Halle, Stefan -- Kertscher, Ilona -- Klein, Alexandra-Maria -- Koller, Robert -- Konig, Stephan -- Kowalski, Esther -- Kummer, Volker -- Kuu, Annely -- Lange, Markus -- Lauterbach, Dirk -- Middelhoff, Cornelius -- Migunova, Varvara D -- Milcu, Alexandru -- Muller, Ramona -- Partsch, Stephan -- Petermann, Jana S -- Renker, Carsten -- Rottstock, Tanja -- Sabais, Alexander -- Scheu, Stefan -- Schumacher, Jens -- Temperton, Vicky M -- Tscharntke, Teja -- England -- Nature. 2010 Nov 25;468(7323):553-6. doi: 10.1038/nature09492. Epub 2010 Oct 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Georg-August-University Gottingen, Department of Crop Sciences, Agroecology, Grisebachstrasse 6, 37077 Gottingen, Germany. christoph.scherber@agr.uni-goettingen.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20981010" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biodiversity ; *Models, Biological ; *Plant Physiological Phenomena ; Population Density
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Climate extremes and the carbon cycle (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-08-21
    Description: The terrestrial biosphere is a key component of the global carbon cycle and its carbon balance is strongly influenced by climate. Continuing environmental changes are thought to increase global terrestrial carbon uptake. But evidence is mounting that climate extremes such as droughts or storms can lead to a decrease in regional ecosystem carbon stocks and therefore have the potential to negate an expected increase in terrestrial carbon uptake. Here we explore the mechanisms and impacts of climate extremes on the terrestrial carbon cycle, and propose a pathway to improve our understanding of present and future impacts of climate extremes on the terrestrial carbon budget.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reichstein, Markus -- Bahn, Michael -- Ciais, Philippe -- Frank, Dorothea -- Mahecha, Miguel D -- Seneviratne, Sonia I -- Zscheischler, Jakob -- Beer, Christian -- Buchmann, Nina -- Frank, David C -- Papale, Dario -- Rammig, Anja -- Smith, Pete -- Thonicke, Kirsten -- van der Velde, Marijn -- Vicca, Sara -- Walz, Ariane -- Wattenbach, Martin -- England -- Nature. 2013 Aug 15;500(7462):287-95. doi: 10.1038/nature12350.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Biogeochemistry, 07745 Jena, Germany. markus.reichstein@bgc-jena.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23955228" target="_blank"〉PubMed〈/a〉
    Keywords: *Carbon Cycle ; *Climate Change ; *Ecosystem ; Plants/metabolism ; Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Timing of the compensation of winter respiratory carbon losses provides explanatory power for net ecosystem productivity of forests (2016)
    Wiley
    Details
    Publication Date: 2016-12-28
    Description: Accurate predictions of net ecosystem productivity (NEP c ) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEP c (e.g. climate, nutrients) are not entirely understood yet, particularly when considering the influence of past periods. Here we explored the explanatory power of the compensation day (cDOY) —defined as the day of year when winter net carbon losses are compensated by spring assimilation— for NEP c in 26 forests in Europe, North America, and Australia, using different NEP c integration methods. We found cDOY to be a particularly powerful predictor for NEP c of temperate evergreen needle-leaf forests (R 2  = 0.58) and deciduous broadleaf forests (R 2  = 0.68). In general, the latest cDOY correlated with the lowest NEP c . The explanatory power of cDOY depended on the integration method for NEP c , forest type, and whether the site had a distinct winter net respiratory carbon loss or not. The integration methods starting in autumn led to better predictions of NEP c from cDOY then the classical calendar method starting at January 1. Limited explanatory power of cDOY for NEP c was found for warmer sites with no distinct winter respiratory loss period. Our findings highlight the importance of the influence of winter processes and the delayed responses of previous seasons’ climatic conditions on current year's NEP c . Such carry-over effects may contain information from climatic conditions, carbon storage levels and hydraulic traits of several years back in time.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Atmospheric nitrogen deposition and canopy retention influences on photosynthetic performance at two high nitrogen deposition Swiss forests (2012)
    Co-Action Publishing
    In: Tellus B
    Details
    Publication Date: 2012-07-28
    Description: Portable chlorophyll fluorometry measurements, providing plant photosynthetic efficiency (PE) data, were carried out at two contrasting Swiss forests experiencing high nitrogen (N) deposition. Fluorometry data were obtained in conjunction with controlled N treatment applications within forest canopies to more realistically simulate deposition of plant-available N species. At the high N deposition Novaggio oak forest, growing season canopy N applications caused increases in PE and other photosynthetic measures. Similar N applications at the Lägeren mixed beech and spruce forest site indicated a possible PE decrease in beech leaves and no effect on spruce needles. N is considered a growth-limiting nutrient in temperate environments where low to moderate N deposition can benefit forest growth; however, high N deposition can have negative effects on forest health and growth due to nutrient imbalances. We conclude that the growth effect dominates at both sites, thereby increasing the potential for carbon sequestration. We found clear evidence of direct leaf-level canopy N uptake in combination with increased PE at the Novaggio oak forest site and no definitive evidence of negative N effects at the Lägeren site. We conclude that PE measurements with chlorophyll fluorometry is a useful tool to quantify N and carbon exchange aspects of deciduous forest dynamics. Keywords: atmospheric nitrogen deposition, fluorometry, canopy nitrogen uptake, photosynthetic efficiency, carbon storage (Published: 27 July 2012) Citation: Tellus B 2012, 64 , 17216, http://dx.doi.org/10.3402/tellusb.v64i0.17216
    Print ISSN: 0280-6509
    Electronic ISSN: 1600-0889
    Topics: Geography , Physics
    Published by Co-Action Publishing on behalf of The International Meteorological Institute in Stockholm.
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  • 5
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    Greenhouse gas fluxes over managed grasslands in Central Europe (2018)
    Wiley
    Details
    Publication Date: 2018-02-06
    Description: Central European grasslands are characterized by a wide range of different management practices in close geographical proximity. Site-specific management strategies strongly affect the biosphere-atmosphere exchange of the three greenhouse gases (GHG) carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and methane (CH 4 ). The evaluation of environmental impacts at site level is challenging, because most in-situ measurements focus on the quantification of CO 2 exchange, while long-term N 2 O and CH 4 flux measurements at ecosystem scale remain scarce. Here, we synthesized ecosystem CO 2 , N 2 O and CH 4 fluxes from 14 managed grassland sites, quantified by eddy covariance or chamber techniques. We found that grasslands were on average a CO 2 sink (-1783 to -91 g CO 2 m −2 yr −1 ), but a N 2 O source (18 – 638 g CO 2 -eq. m −2 yr −1 ), and either a CH 4 sink or source (-9 to 488 g CO 2 -eq. m −2 yr −1 ). The net GHG balance (NGB) of nine sites where measurements of all three GHGs were available was found between -2761 and -58 g CO 2 -eq. m −2 yr −1 , with N 2 O and CH 4 emissions offsetting concurrent CO 2 uptake by on average 21 ± 6% across sites. The only positive NGB was found for one site during a restoration year with ploughing. The predictive power of soil parameters for N 2 O and CH 4 fluxes was generally low and varied considerably within years. However, after site-specific data normalization we identified environmental conditions that indicated enhanced GHG source/sink activity (‘sweet spots’) and gave a good prediction of normalized overall fluxes across sites. The application of animal slurry to grasslands increased N 2 O and CH 4 emissions. The N 2 O-N emission factor across sites was 1.8 ± 0.5%, but varied considerably at site level among the years (0.1 – 8.6%). Although grassland management lead to increased N 2 O and CH 4 emissions, the CO 2 sink strength was generally the most dominant component of the annual GHG budget. This article is protected by copyright. All rights reserved.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 6
    Electronic Resource
    Electronic Resource
    Productivity overshadows temperature in determining soil and ecosystem respiration across European forests (2001)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 7 (2001), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: This paper presents CO2 flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1 (mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil respiration (SR) was 760 ± 340 gC m−2 y−1 (55% of GPP and 69% of TER).Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature.At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated fromthe relationship between annual SR (and TER) and GPP observed among the less-disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2001.00412.x
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  • 7
    Electronic Resource
    Electronic Resource
    Carbon isotope composition of C4 grasses is influenced by light and water supply (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The carbon isotope composition of C4 grasses has the potential to be used as an indicator of changes in the isotopic composition and concentration of atmospheric CO2, especially for climate reconstruction. The usefulness of C4 grasses for this purpose hinges on the assumption that their photosynthetic discrimination against 13C remains constant in a wide range of environmental conditions. We tested this assumption by examining the effects of light and water stress on the carbon isotope composition of C4 grasses using different biochemical subtypes (NADP-ME, NAD-ME, PCK) in glasshouse experiments. We grew 14 different C4 grass species in four treatments: sun-watered, sun-drought, shade-watered and shade-drought. Carbon isotope discrimination (Δ) rarely remained constant. In general, Δ values were lowest in sun-watered grasses, greater for sun-drought plants and even higher for plants of the shade-watered treatment. The highest Δ values were generally found in the most stressed grasses, the shade-drought plants. Grasses of the NADP-ME subtype were the least influenced by a change in environmental variables, followed by PCK and NAD-ME subtypes. Water availability affected the carbon isotope discrimination less than light limitation in PCK and NAD-ME subtypes, but similarly in NADP-ME subtypes.In another experiment, we studied the effect of increasing light levels (150 to 1500 μmol photons m−2 s−1) on the Δ values of 18 well-watered C4 grass species. Carbon isotope discrimination remained constant until photon flux density (PFD) was less than 700 μmol photons m−2 s−1. Below this light level, Δ values increased with decreasing irradiance for all biochemical subtypes. The change in A was less pronounced in NADP-ME and PCK than in NAD-ME grasses. Grasses grown in the field and in the glasshouse showed a similar pattern. Thus, caution should be exercised when using C4 plants under varying environmental conditions to monitor the concentration or carbon isotopic composition of atmospheric CO2 in field/glasshouse studies or climate reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00331.x
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  • 8
    Electronic Resource
    Electronic Resource
    15N-ammonium and 15N-nitrate uptake of a 15-year-old Picea abies plantation (1995)
    Springer
    Oecologia 102 (1995), S. 361-370 
    Details
    ISSN: 1432-1939
    Keywords: Picea abies (L.) Karst ; Ammonium ; Nitrate ; 15N ; Tracer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Throughfall nitrogen of a 15-year-old Picea abies (L.) Karst. (Norway spruce) stand in the Fichtelgebirge, Germany, was labeled with either 15N-ammonium or 15N-nitrate and uptake of these two tracers was followed during two successive growing seasons (1991 and 1992). 15N-labeling (62 mg 15N m-2 under conditions of 1.5 g N m-2 atmospheric nitrogen deposition) did not increase N concentrations in plant tissues. The 15N recovery within the entire stand (including soils) was 94%±6% of the applied 15N-ammonium tracer and 100%±6% of the applied 15N-nitrate tracer during the 1st year of investigation. This decreased to 80%±24% and 83%±20%, respectively, during the 2nd year. After 11 days, the 15N tracer was detectable in 1-year-old spruce needles and leaves of understory species. After 1 month, tracer was detectable in needle litter fall. At the end of the first growing season, more than 50% of the 15N taken up by spruce was assimilated in needles, and more than 20% in twigs. The relative distribution of recovered tracer of both 15N-ammonium and 15N-nitrate was similar within the different foliage age classes (recent to 11-year-old) and other compartments of the trees. 15N enrichment generally decreased with increasing tissue age. Roots accounted for up to 20% of the recovered 15N in spruce; no enrichment could be detected in stem wood. Although 15N-ammonium and 15N-nitrate were applied in the same molar quantities (15NH 4 + : 15NO 3 - =1:1), the tracers were diluted differently in the inorganic soil N pools (15NH 4 + /NH 4 + : 15NO 3 - /NO 3 - =1:9). Therefore the measured 15N amounts retained by the vegetation do not represent the actual fluxes of ammonium and nitrate in the soil solution. Use of the molar ammonium-to-nitrate ratio of 9:1 in the soil water extract to estimate 15N uptake from inorganic N pools resulted in a 2–4 times higher ammonium than nitrate uptake by P. abies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329803
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  • 9
    Electronic Resource
    Electronic Resource
    Interseasonal comparison of CO2 concentrations, isotopic composition, and carbon dynamics in an Amazonian rainforest (French Guiana) (1997)
    Springer
    Oecologia 110 (1997), S. 120-131 
    Details
    ISSN: 1432-1939
    Keywords: Key words Carbon discrimination  ;  δ13C  ;  δ18O  ;  Canopy CO2 profiles  ;  Soil respiration.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Canopy CO2 concentrations in a tropical rainforest in French Guiana were measured continuously for 5 days during the 1994 dry season and the 1995 wet season. Carbon dioxide concentrations ([CO2]) throughout the canopy (0.02–38 m) showed a distinct daily pattern, were well-stratified and decreased with increasing height into the canopy. During both seasons, daytime [CO2] in the upper and middle canopy decreased on average 7–10 μmol mol−1 below tropospheric baseline values measured at Barbados. Within the main part of the canopy (≥ 0.7 m), [CO2] did not differ between the wet and dry seasons. In contrast, [CO2] below 0.7 m were generally higher during the dry season, resulting in larger [CO2] gradients. Supporting this observation, soil CO2 efflux was on average higher during the dry season than during the wet season, either due to diffusive limitations and/or to oxygen deficiency of root and microbial respiration. Soil respiration rates decreased by 40% after strong rain events, resulting in a rapid decrease in canopy [CO2] immediately above the forest floor of about 50␣μmol mol−1. Temporal and spatial variations in [CO2]canopy were reflected in changes of δ13Ccanopy and δ18Ocanopy values. Tight relationships were observed between δ13C and δ18O of canopy CO2 during both seasons (r 2 〉 0.86). The most depleted δ13Ccanopy and δ18Ocanopy values were measured immediately above the forest floor (δ13C = −16.4‰; δ18O = 39.1‰ SMOW). Gradients in the isotope ratios of CO2 between the top of the canopy and the forest floor ranged between 2.0‰ and 6.3‰ for δ13C, and between 1.0‰ and 3.5‰ for δ18O. The δ13Cleaf and calculated c i/c a of foliage at three different positions were similar for the dry and wet seasons indicating that the canopy maintained a constant ratio of photosynthesis to stomatal conductance. About 20% of the differences in δ13Cleaf within the canopy was accounted for by source air effects, the remaining 80% must be due to changes in c i/c a. Plotting 1/[CO2] vs. the corresponding δ13C ratios resulted in very tight, linear relationships (r 2 = 0.99), with no significant differences between the two seasons, suggesting negligible seasonal variability in turbulent mixing relative to ecosystem gas exchange. The intercepts of these relationships that should be indicative of the δ13C of respired sources were close to the measured δ13C of soil respired CO2 and to the δ13C of litter and soil organic matter. Estimates of carbon isotope discrimination of the entire ecosystem, Δe, were calculated as 20.3‰ during the dry season and as 20.5‰ during the wet season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050140
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of stand structure on carbon-13 of vegetation, soils, and canopy air within deciduous and evergreen forests in Utah, United States (1997)
    Springer
    Oecologia 110 (1997), S. 109-119 
    Details
    ISSN: 1432-1939
    Keywords: Key words CO2  ;  δ13C  ;  Ecosystem discrimination  ;   Soil respiration  ;  Temporal and spatial variation 
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbon isotope ratios (δ13C) were studied in evergreen and deciduous forest ecosystems in semi-arid Utah (Pinus contorta, Populus tremuloides, Acer negundo and Acer grandidentatum). Measurements were taken in four to five stands of each forest ecosystem differing in overstory leaf area index (LAI) during two consecutive growing seasons. The δ13Cleaf (and carbon isotope discrimination) of understory vegetation in the evergreen stands (LAI 1.5–2.2) did not differ among canopies with increasing LAI, whereas understory in the deciduous stands (LAI 1.5–4.5) exhibited strongly decreasing δ13Cleaf values (increasing carbon isotope discrimination) with increasing LAI. The δ13C values of needles and leaves at the top of the canopy were relatively constant over the entire LAI range, indicating no change in intrinsic water-use efficiency with overstory LAI. In all canopies, δ13Cleaf decreased with decreasing height above the forest floor, primarily due to physiological changes affecting c i/c a (〉 60%) and to a minor extent due to δ13C of canopy air (〈 40%). This intra-canopy depletion of δ13Cleaf was lowest in the open stand (1‰) and greatest in the denser stands (4.5‰). Although overstory δ13Cleaf did not change with canopy LAI, δ13C of soil organic carbon increased with increasing LAI in Pinus contorta and Populus tremuloides ecosystems. In addition, δ13C of decomposing organic carbon became increasingly enriched over time (by 1.7–2.9‰) for all deciduous and evergreen dry temperate forests. The δ13Ccanopy of CO2 in canopy air varied temporally and spatially in all forest stands. Vertical canopy gradients of δ13Ccanopy, and [CO2]canopy were larger in the deciduous Populus tremuloides than in the evergreen Pinu contorta stands of similar LAI. In a very wet and cool year, ecosystem discrimination (Δe) was similar for both deciduous Populus tremulodies (18.0 ± 0.7‰) and evergreen Pinus contorta (18.3 ± 0.9‰) stands. Gradients of δ13Ccanopy and [CO2]canopy were larger in denser Acer spp. stands than those in the open stand. However, 13C enrichment above and photosynthetic draw-down of [CO2]canopy below tropospheric baseline values were larger in the open than in the dense stands, due to the presence of a vigorous understory vegetation. Seasonal patterns of the relationship δ13Ccanopy versus 1/[CO2]canopy were strongly influenced by precipitation and air temperature during the growing season. Estimates of Δe for Acer spp. did not show a significant effect of stand structure, and averaged 16.8 ± 0.5‰ in 1933 and 17.4 ± 0.7‰ in 1994. However, Δe varied seasonally with small fluctuations for the open stand (2‰), but more pronounced changes for the dense stand (5‰).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050139
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