Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Global variability in leaf respiration in relation to climate, plant functional types and leaf traits
    Atkin, O. ; Bloomfield, K. ; Reich, P.B. ; Tjoelker, M.G. ; Asner, G. ; Bonal, D. ; Bönisch, G. ; Poorter, L. - \ 2015
    New Phytologist 206 (2015)2. - ISSN 0028-646X - p. 614 - 636.
    elevated atmospheric co2 - terrestrial carbon-cycle - tropical rain-forests - dark respiration - thermal-acclimation - temperature sensitivity - vegetation models - photosynthetic capacity - nitrogen concentration - scaling relationships
    Leaf dark respiration (R-dark) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of R-dark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed-effects models were used to disentangle sources of variation in R-dark. Area-based R-dark at the prevailing average daily growth temperature (T) of each siteincreased only twofold from the Arctic to the tropics, despite a 20 degrees C increase in growing T (8-28 degrees C). By contrast, R-dark at a standard T (25 degrees C, R-dark(25)) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher R-dark(25) at a given photosynthetic capacity (V-cmax(25)) or leaf nitrogen concentration ([N]) than species at warmer sites. R-dark(25) values at any given V-cmax(25) or [N] were higher in herbs than in woody plants. The results highlight variation in R-dark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of R-dark in terrestrial biosphere models (TBMs) and associated land-surface components of Earth system models (ESMs).
    Ozone affects growth and development of Pieris brassicae on the wild host plant Brassica nigra
    Khaling, E. ; Papazian, S. ; Poelman, E.H. ; Holopainen, J.K. ; Albrectsen, B.R. ; Blande, J.D. - \ 2015
    Environmental Pollution 199 (2015). - ISSN 0269-7491 - p. 119 - 129.
    elevated atmospheric co2 - beetle epilachna-varivestis - betula-pendula roth - glucosinolate concentrations - secondary metabolites - feeding preference - oviposition preference - specialist herbivores - plutella-xylostella - leaf beetle
    When plants are exposed to ozone they exhibit changes in both primary and secondary metabolism, which may affect their interactions with herbivorous insects. Here we investigated the performance and preferences of the specialist herbivore Pieris brassicae on the wild plant Brassica nigra under elevated ozone conditions. The direct and indirect effects of ozone on the plant-herbivore system were studied. In both cases ozone exposure had a negative effect on P. brassicae development. However, in dual-choice tests larvae preferentially consumed plant material previously fumigated with the highest concentration tested, showing a lack of correlation between larval preference and performance on ozone exposed plants. Metabolomic analysis of leaf material subjected to combinations of ozone and herbivore-feeding, and focussing on known defence metabolites, indicated that P. brassicae behaviour and performance were associated with ozone-induced alterations to glucosinolate and phenolic pools.
    Going back to the roots: the microbial ecology of the rhizosphere
    Philippot, L. ; Raaijmakers, J. ; Lemanceau, P. ; Putten, W.H. van der - \ 2013
    Nature Reviews Microbiology 11 (2013)11. - ISSN 1740-1526 - p. 789 - 799.
    arbuscular mycorrhizal fungi - bacterial community structure - disease-suppressive bacteria - gradient gel-electrophoresis - plant-herbivore interactions - elevated atmospheric co2 - soil-borne pathogens - medicago-truncatula - food webs - arabidopsis-thaliana
    The rhizosphere is the interface between plant roots and soil where interactions among a myriad of microorganisms and invertebrates affect biogeochemical cycling, plant growth and tolerance to biotic and abiotic stress. The rhizosphere is intriguingly complex and dynamic, and understanding its ecology and evolution is key to enhancing plant productivity and ecosystem functioning. Novel insights into key factors and evolutionary processes shaping the rhizosphere microbiome will greatly benefit from integrating reductionist and systems-based approaches in both agricultural and natural ecosystems. Here, we discuss recent developments in rhizosphere research in relation to assessing the contribution of the micro- and macroflora to sustainable agriculture, nature conservation, the development of bio-energy crops and the mitigation of climate change.
    Simple additive effects are rare: a quantitative review of plant biomass and soil process responses to combined manipulations of CO2 and temperature
    Dieleman, W. ; Vicca, S. ; Dijkstra, F.A. ; Hoosbeek, M.R. - \ 2012
    Global Change Biology 18 (2012)9. - ISSN 1354-1013 - p. 2681 - 2693.
    elevated atmospheric co2 - global environmental-changes - carbon-cycle feedback - climate-change - terrestrial ecosystems - forest ecosystems - thermal-acclimation - heterotrophic respiration - semiarid grassland - nitrogen cycles
    In recent years, increased awareness of the potential interactions between rising atmospheric CO2 concentrations ([ CO2 ]) and temperature has illustrated the importance of multifactorial ecosystem manipulation experiments for validating Earth System models. To address the urgent need for increased understanding of responses in multifactorial experiments, this article synthesizes how ecosystem productivity and soil processes respond to combined warming and [ CO2 ] manipulation, and compares it with those obtained in single factor [ CO2 ] and temperature manipulation experiments. Across all combined elevated [ CO2 ] and warming experiments, biomass production and soil respiration were typically enhanced. Responses to the combined treatment were more similar to those in the [ CO2 ]-only treatment than to those in the warming-only treatment. In contrast to warming-only experiments, both the combined and the [ CO2 ]-only treatments elicited larger stimulation of fine root biomass than of aboveground biomass, consistently stimulated soil respiration, and decreased foliar nitrogen (N) concentration. Nonetheless, mineral N availability declined less in the combined treatment than in the [ CO2 ]-only treatment, possibly due to the warming-induced acceleration of decomposition, implying that progressive nitrogen limitation (PNL) may not occur as commonly as anticipated from single factor [ CO2 ] treatment studies. Responses of total plant biomass, especially of aboveground biomass, revealed antagonistic interactions between elevated [ CO2 ] and warming, i.e. the response to the combined treatment was usually less-than-additive. This implies that productivity projections might be overestimated when models are parameterized based on single factor responses. Our results highlight the need for more (and especially more long-term) multifactor manipulation experiments. Because single factor CO2 responses often dominated over warming responses in the combined treatments, our results also suggest that projected responses to future global warming in Earth System models should not be parameterized using single factor warming experiments.
    Increasing liana abundance and biomass in tropical forests: emerging patterns and putative mechanisms.
    Schnitzer, S.A. ; Bongers, F. - \ 2011
    Ecology Letters 14 (2011)4. - ISSN 1461-023X - p. 397 - 406.
    below-ground competition - barro-colorado island - ivy toxicodendron radicans - elevated atmospheric co2 - future climate-change - rain-forest - eastern amazonia - aboveground biomass - toxicity responses - temperate forests
    Tropical forests are experiencing large-scale structural changes, the most apparent of which may be the increase in liana (woody vine) abundance and biomass. Lianas permeate most lowland tropical forests, where they can have a huge effect on tree diversity, recruitment, growth and survival, which, in turn, can alter tree community composition, carbon storage and carbon, nutrient and water fluxes. Consequently, increasing liana abundance and biomass have potentially profound ramifications for tropical forest composition and functioning. Currently, eight studies support the pattern of increasing liana abundance and biomass in American tropical and subtropical forests, whereas two studies, both from Africa, do not. The putative mechanisms to explain increasing lianas include increasing evapotranspirative demand, increasing forest disturbance and turnover, changes in land use and fragmentation and elevated atmospheric CO2. Each of these mechanisms probably contributes to the observed patterns of increasing liana abundance and biomass, and the mechanisms are likely to be interrelated and synergistic. To determine whether liana increases are occurring throughout the tropics and to determine the mechanisms responsible for the observed patterns, a widespread network of large-scale, long-term monitoring plots combined with observational and manipulative studies that more directly investigate the putative mechanisms are essential.
    Plant molecular stress responses face climate change. Trends in Plants
    Ahuja, I. ; Vos, R.C.H. de; Bones, A.M. ; Hall, R.D. - \ 2010
    Trends in Plant Science 15 (2010)12. - ISSN 1360-1385 - p. 664 - 674.
    transgenic arabidopsis plants - elevated atmospheric co2 - drought-stress - abiotic stress - transcription factor - gene-expression - heat-stress - systems biology - carbon metabolism - plasma-membrane
    Environmental stress factors such as drought, elevated temperature, salinity and rising CO2 affect plant growth and pose a growing threat to sustainable agriculture. This has become a hot issue due to concerns about the effects of climate change on plant resources, biodiversity and global food security. Plant adaptation to stress involves key changes in the ‘-omic’ architecture. Here, we present an overview of the physiological and molecular programs in stress adaptation focusing on how genes, proteins and metabolites change after individual and multiple environmental stresses. We address the role which ‘-omics’ research, coupled to systems biology approaches, can play in future research on plants seemingly unable to adapt as well as those which can tolerate climatic change.
    Modelling impacts of changes in carbon dioxide concentration, climate and nitrogen deposition on carbon sequestration by European forests and forest soils
    Wamelink, G.W.W. ; Wieggers, H.J.J. ; Reinds, G.J. ; Kros, J. ; Mol-Dijkstra, J.P. ; Oijen, M. van; Vries, W. de - \ 2009
    Forest Ecology and Management 258 (2009)8. - ISSN 0378-1127 - p. 1794 - 1805.
    elevated atmospheric co2 - plant-growth - productivity - ecosystems - temperate - responses - canopy - face - metaanalysis - predictions
    Changes in the Earth's atmosphere are expected to influence the growth, and therefore, carbon accumulation of European forests. We identify three major changes: (1) a rise in carbon dioxide concentration, (2) climate change, resulting in higher temperatures and changes in precipitation and (3) a decrease in nitrogen deposition. We adjusted and applied the hydrological model Watbal, the soil model SMART2 and the vegetation model SUMO2 to asses the effect of expected changes in the period 1990 up to 2070 on the carbon accumulation in trees and soils of 166 European forest plots. The models were parameterized using measured soil and vegetation parameters and site-specific changes in temperature, precipitation and nitrogen deposition. The carbon dioxide concentration was assumed to rise uniformly across Europe. The results were compared to a reference scenario consisting of a constant CO2 concentration and deposition scenario. The temperature and precipitation scenario was a repetition of the period between 1960 and 1990. All scenarios were compared to the reference scenario for biomass growth and carbon sequestration for both the soil and the trees. The predicted effects of changes in climate, CO2 concentration and nitrogen deposition on carbon sequestration by trees depend largely on tree species and location (latitude). The assumed decrease in nitrogen deposition causes a decrease of carbon accumulation all over Europe and for all modelled tree species. A rise in carbon dioxide concentration gives a rise in carbon accumulation all over Europe. Climate change gives a mixed result, with a decrease in carbon accumulation in the South of Europe and an increase in the North. When the scenarios are combined, an increase in biomass accumulation is predicted at most of the sites, with a rise in growth rate mostly between 0 and 100%. The predicted effects of a change in climate, CO2 concentration and nitrogen deposition on soil carbon sequestration is generally lower than the effect on carbon sequestration by the trees. However, the magnitude is similar as is the location effect (latitude). A net carbon release was predicted at several sites in the south due to the effect of climate change. Overall, we conclude that where nitrogen deposition was a major driver for a change in forest growth in the past, it is climate change, and to a lesser extent CO2 change, that will influence forest growth in the future.
    Ectomycorrhizal fungi associated with Pinus sylvestris seedlings respond differently to increased carbon and nitrogen availability: implications for ecosystem responses to global change.
    Alberton, O. ; Kuyper, T.W. - \ 2009
    Global Change Biology 15 (2009)1. - ISSN 1354-1013 - p. 166 - 175.
    elevated atmospheric co2 - progressive n limitation - douglas-fir seedlings - terrestrial ecosystems - deposition gradient - mycorrhizal fungal - community change - soil biota - dioxide - metaanalysis
    The ectomycorrhizal (ECM) symbiosis can cause both positive and negative feedback with trees under elevated CO2. Positive feedback arises if the additional carbon (C) increases both nutrient uptake by the fungus and nutrient transfer to the plant, whereas negative feedback results from increased nutrient uptake and immobilization by the fungus and reduced transfer to the plant. Because species of ECM fungi differ in their C and nitrogen (N) demand, understanding fungal species-specific responses to variation in C and N supply is essential to predict impacts of global change. We investigated fungal species-specific responses of ECM Scots pine (Pinus sylvestris) seedlings under ambient and elevated CO2 (350 or 700 ¿L L¿1 CO2) and under low and high mineral N availability. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor and Suillus bovinus. The experiment lasted 103 days. During the final 27 days, seedlings were labeled with 14CO2 and 15N. Most plant and fungal parameters were significantly affected by fungal species, CO2 level and N supply. Interactions between fungal species and CO2 were also regularly significant. At low N availability, elevated CO2 had the smallest impact on the photosynthetic performance of seedlings inoculated with H. cylindrosporum and the largest impact on seedlings with S. bovinus. At ambient CO2, increasing N supply had the smallest impact on seedlings inoculated with S. bovinus and the largest on seedlings inoculated with H. cylindrosporum. At low N availability, extraradical hyphal length increased after doubling CO2 level, but this was significant only for L. bicolor. At ambient CO2, increasing N levels reduced hyphal length for both H. cylindrosporum and S. bovinus, but not for L. bicolor. We discuss the potential interplay of two major elements of global change, elevated CO2 and increased N availability, and their effects on plant growth. We conclude that increased N supply potentially relieves mycorrhiza-induced progressive N limitation under elevated CO2
    Coppicing shifts CO2 stimulation of poplar productivity to above-ground pools: a synthesis of leaf to stand level results from the POP/EUROFACE experiment
    Liberloo, M. ; Lukac, M. ; Calfapietra, C. ; Hoosbeek, M.R. ; Gielen, B. ; Miglietta, F. ; Mugnozza, G.S. ; Ceulemans, R. - \ 2009
    New Phytologist 182 (2009)2. - ISSN 0028-646X - p. 331 - 346.
    elevated atmospheric co2 - progressive nitrogen limitation - carbon-dioxide enrichment - short-rotation coppice - net primary production - warm-temperate forest - stomatal conductance - deciduous forest - n-fertilization - soil carbon
    A poplar short rotation coppice (SRC) grown for the production of bioenergy can combine carbon (C) storage with fossil fuel substitution. Here, we summarize the responses of a poplar (Populus) plantation to 6 yr of free air CO2 enrichment (POP/EUROFACE consisting of two rotation cycles). We show that a poplar plantation growing in nonlimiting light, nutrient and water conditions will significantly increase its productivity in elevated CO2 concentrations ([CO2]). Increased biomass yield resulted from an early growth enhancement and photosynthesis did not acclimate to elevated [CO2]. Sufficient nutrient availability, increased nitrogen use efficiency (NUE) and the large sink capacity of poplars contributed to the sustained increase in C uptake over 6 yr. Additional C taken up in high [CO2] was mainly invested into woody biomass pools. Coppicing increased yield by 66% and partly shifted the extra C uptake in elevated [CO2] to above-ground pools, as fine root biomass declined and its [CO2] stimulation disappeared. Mineral soil C increased equally in ambient and elevated [CO2] during the 6 yr experiment. However, elevated [CO2] increased the stabilization of C in the mineral soil. Increased productivity of a poplar SRC in elevated [CO2] may allow shorter rotation cycles, enhancing the viability of SRC for biofuel production
    Hierarchical saturation of soil carbon pools near a natural CO2 spring
    Kool, D.M. ; Chung, H. ; Tate, K.R. ; Ross, D.J. ; Newton, P.C.D. ; Six, J. - \ 2007
    Global Change Biology 13 (2007)6. - ISSN 1354-1013 - p. 1282 - 1293.
    elevated atmospheric co2 - long-term exposure - organic-matter - nitrogen limitation - no-tillage - aggregate stability - agricultural soils - grassland - dioxide - sequestration
    Soil has been identified as a possible carbon (C) sink to mitigate increasing atmospheric CO2 concentration. However, several recent studies have suggested that the potential of soil to sequester C is limited and that soil may become saturated with C under increasing CO2 levels. To test this concept of soil C saturation, we studied a gley and organic soil at a grassland site near a natural CO2 spring. Total and aggregate-associated soil organic C (SOC) concentration showed a significant increase with atmospheric CO2 concentration. An asymptotic function showed a better fit of SOC and aggregation with CO2 level than a linear model. There was a shift in allocation of total C from smaller size fractions to the largest aggregate fraction with increasing CO2 concentration. Litter inputs appeared to be positively related to CO2 concentration. Based on modeled function parameters and the observed shift in the allocation of the soil C from small to large aggregate-size classes, we postulate that there is a hierarchy in C saturation across different SOC pools. We conclude that the asymptotic response of SOC concentration at higher CO2 levels indicates saturation of soil C pools, likely because of a limit to physical protection of SOC.
    Specific root length as an indicator of environmental change
    Ostonen, I. ; Püttsepp, Ü. ; Biel, C. ; Alberton, O. ; Bakker, M.R. ; Löhmus, K. ; Majdi, H. ; Metcalfe, J.D. ; Olsthoorn, A.F.M. ; Pronk, A.A. ; Vanguelova, E. ; Weih, M. ; Brunner, I. - \ 2007
    Plant Biosystems 141 (2007)3. - ISSN 1126-3504 - p. 426 - 442.
    spruce picea-abies - elevated atmospheric co2 - pine pinus-sylvestris - soil solution chemistry - potential growth-rate - fine-root - norway spruce - l. karst. - nutrient availability - silver birch
    Specific root length (SRL, m g-1) is probably the most frequently measured morphological parameter of fine roots. It is believed to characterize economic aspects of the root system and to be indicative of environmental changes. The main objectives of this paper were to review and summarize the published SRL data for different tree species throughout Europe and to assess SRL under varying environmental conditions. Meta-analysis was used to summarize the response of SRL to the following manipulated environmental conditions: fertilization, irrigation, elevated temperature, elevated CO2, Al-stress, reduced light, heavy metal stress and physical disturbance of soil. SRL was found to be strongly dependent on the fine root classes, i.e. on the ectomycorrhizal short roots (ECM), and on the roots
    Total soil C and N sequestration in a grassland following 10 years of free air CO2 enrichment
    Kessel, C. van; Boots, B. ; Graaff, M.A. de; Harris, D. ; Blum, H. ; Six, J. - \ 2006
    Global Change Biology 12 (2006)11. - ISSN 1354-1013 - p. 2187 - 2199.
    elevated atmospheric co2 - trifolium-repens l - organic-matter - carbon-dioxide - lolium-perenne - n-15-labeled fertilizer - litter quality - nitrogen pools - forest soils - plant
    Soil C sequestration may mitigate rising levels of atmospheric CO2. However, it has yet to be determined whether net soil C sequestration occurs in N-rich grasslands exposed to long-term elevated CO2. This study examined whether N-fertilized grasslands exposed to elevated CO2 sequestered additional C. For 10 years, Lolium perenne, Trifolium repens, and the mixture of L. perenne/T. repens grasslands were exposed to ambient and elevated CO2 concentrations (35 and 60 Pa pCO(2)). The applied CO2 was depleted in delta C-13 and the grasslands received low (140 kg ha(-1)) and high (560 kg ha(-1)) rates of N-15-labeled fertilizer. Annually collected soil samples from the top 10 cm of the grassland soils allowed us to follow the sequestration of new C in the surface soil layer. For the first time, we were able to collect dual-labeled soil samples to a depth of 75 cm after 10 years of elevated CO2 and determine the total amount of new soil C and N sequestered in the whole soil profile. Elevated CO2, N-fertilization rate, and species had no significant effect on total soil C. On average 9.4 Mg new C ha(-1) was sequestered, which corresponds to 26.5% of the total C. The mean residence time of the C present in the 0-10 cm soil depth was calculated at 4.6 +/- 1.5 and 3.1 +/- 1.1 years for L. perenne and T. repens soil, respectively. After 10 years, total soil N and C in the 0-75 cm soil depth was unaffected by CO2 concentration, N-fertilization rate and plant species. The total amount of N-15-fertilizer sequestered in the 0-75 cm soil depth was also unaffected by CO2 concentration, but significantly more N-15 was sequestered in the L. perenne compared with the T. repens swards: 620 vs. 452 kg ha(-1) at the high rate and 234 vs. 133 kg ha(-1) at the low rate of N fertilization. Intermediate values of N-15 recovery were found in the mixture. The fertilizer derived N amounted to 2.8% of total N for the low rate and increased to 8.6% for the high rate of N application. On average, 13.9% of the applied N-15-fertilizer was recovered in the 0-75 cm soil depth in soil organic matter in the L. perenne sward, whereas 8.8% was recovered under the T. repens swards, indicating that the N-2-fixing T. repens system was less effective in sequestering applied N than the non-N-2-fixing L. perenne system. Prolonged elevated CO2 did not lead to an increase in whole soil profile C and N in these fertilized pastures. The potential use of fertilized and regular cut pastures as a net soil C sink under long-term elevated CO2 appears to be limited and will likely not significantly contribute to the mitigation of anthropogenic C emissions.
    Element interactions limit soil carbon storage
    Groenigen, K.J. van; Six, J. ; Hungate, B.A. ; Graaff, M.A. de; Breemen, N. van; Kessel, C. van - \ 2006
    Proceedings of the National Academy of Sciences of the United States of America 103 (2006)17. - ISSN 0027-8424 - p. 6571 - 6574.
    elevated atmospheric co2 - biological nitrogen-fixation - ecosystem responses - climate-change - fine roots - grassland - forest - model - cycles - metaanalysis
    Rising levels of atmospheric CO2 are thought to increase C sinks in terrestrial ecosystems. The potential of these sinks to mitigate CO2 emissions, however, may be constrained by nutrients. By using metaanalysis, we found that elevated CO2 only causes accumulation of soil C when N is added at rates well above typical atmospheric N inputs. Similarly, elevated CO2 only enhances N-2 fixation, the major natural process providing soil N input, when other nutrients (e.g., phosphorus, molybdenum, and potassium) are added. Hence, soil C sequestration under elevated CO2 is constrained both directly by IN availability and indirectly by nutrients needed to support N2 fixation.
    Climate change impacts on wheat production in a Mediterranean environment in Western Australia
    Ludwig, F. ; Asseng, S. - \ 2006
    Agricultural Systems 90 (2006)1-3. - ISSN 0308-521X - p. 159 - 179.
    elevated atmospheric co2 - carbon-dioxide - water-deficit - simulation-models - change scenarios - yield response - use efficiency - deep drainage - winter-wheat - temperature
    The environment in which crops will be grown in the future will change. CO2 concentrations [CO2] and temperatures (T) will probably increase and a decline of winter rainfall is predicted for south-west Australia. To be able to adapt crop systems to a changing climate it is important to know how different aspects of climate change affect agricultural production and how they interact. In a full factorial design we studied how higher T (2, 4 and 6 °C) elevated [CO2] (525 and 700 ppm) and five different rainfall scenarios affected wheat yield and grain protein. Effects of climate change were simulated with the Agricultural Production Systems Simulator (APSIM-Nwheat) using transformed historic weather data. Fifty years of yield and grain protein concentrations were simulated for three soil types at different locations on a north¿south transect within the wheatbelt of south-west Australia. Simulation results showed that there were complex interactions between different aspects of climate change on crop systems. Effects of higher temperatures, elevated [CO2] and changed rainfall were in general not linear and differed significantly between soil types and location. Higher [CO2] increased yield especially at drier sites while higher temperatures had a positive effect in the cooler and wetter southern part of the region. The main difference between soil types was that heavier clay soils are most vulnerable to reduced rainfall while sandy soils were more vulnerable to higher temperatures. Elevated [CO2] reduced grain protein concentration and lower rainfall increased protein levels at all sites. Higher temperatures could both increase and decrease protein concentrations. In the southern, higher rainfall part of south-western Australia, yield and gross margin will increase for all likely future climate scenarios. In the drier part of the region, negative effects of 15% reduced rainfall can be compensated for by a 2 °C increase in temperature and 50% higher [CO2] concentrations. However due to the non-linearity of climate change effects a 30% reduction in rainfall cannot be compensated for by higher temperatures and [CO2].
    Mycorrhizal hyphal turnover as a dominant process for carbon input into soil organic matter
    Godbold, D. ; Hoosbeek, M.R. ; Lukac, M. ; Francesca Cotrufo, M. ; Janssens, I.A. ; Ceulemans, R. ; Polle, A. ; Velthorst, E.J. ; Scarascia-Mugnozza, G. ; Angelis, P. de; Miglietta, F. ; Peressotti, A. - \ 2006
    Plant and Soil 281 (2006)1-2. - ISSN 0032-079X - p. 15 - 24.
    elevated atmospheric co2 - douglas-fir ecosystem - 1st growing-season - ectomycorrhizal fungi - forest ecosystems - external mycelium - root turnover - enrichment - nitrogen - patterns
    The atmospheric concentration of CO2 is predicted to reach double current levels by 2075. Detritus from aboveground and belowground plant parts constitutes the primary source of C for soil organic matter (SOM), and accumulation of SOM in forests may provide a significant mechanism to mitigate increasing atmospheric CO2 concentrations. In a poplar (three species) plantation exposed to ambient (380 ppm) and elevated (580 ppm) atmospheric CO2 concentrations using a Free Air Carbon Dioxide Enrichment (FACE) system, the relative importance of leaf litter decomposition, fine root and fungal turnover for C incorporation into SOM was investigated. A technique using cores of soil in which a C-4 crop has been grown (delta C-13 -18.1 parts per thousand) inserted into the plantation and detritus from C-3 trees (delta C-13 -27 to -30 parts per thousand) was used to distinguish between old (native soil) and new (tree derived) soil C. In-growth cores using a fine mesh (39 mu m) to prevent in-growth of roots, but allow in-growth of fungal hyphae were used to assess contribution of fine roots and the mycorrhizal external mycelium to soil C during a period of three growing seasons (1999-2001). Across all species and treatments, the mycorrhizal external mycelium was the dominant pathway (62%) through which carbon entered the SOM pool, exceeding the input via leaf litter and fine root turnover. The input via the mycorrhizal external mycelium was not influenced by elevated CO2, but elevated atmospheric CO2 enhanced soil C inputs via fine root turnover. The turnover of the mycorrhizal external mycelium may be a fundamental mechanism for the transfer of root-derived C to SOM.
    Global change and agro-forest ecosystems: Adaptation and mitigation in a FACE experiment on a poplar plantation
    Scarascia-Mugnozza, G. ; Angelis, P. de; Sabatti, M. ; Calfapietra, C. ; Miglietta, F. ; Raines, C. ; Godbold, D. ; Hoosbeek, M.R. ; Taylor, G. ; Polle, A. ; Ceulemans, R. - \ 2005
    Plant Biosystems 139 (2005)3. - ISSN 1126-3504 - p. 255 - 264.
    elevated atmospheric co2 - carbon-dioxide - enrichment popface - short-rotation - mycorrhizal colonization - betula-papyrifera - field - responses - growth - soil
    The objective of this research was to determine the functional responses of a cultivated, agro-forestry system, namely a poplar plantation, to actual and future atmospheric CO2 concentrations. Hence, this research has combined a fast growing, agro-forestry ecosystem, capable of elevated biomass production, with a large-scale Free Air Carbon Enrichment (FACE) system, one of the few available in the European Union on a forest tree stand. The FACE facility is located close to a natural CO2 source and is drawing scientists from several European countries, and from other continents, to closely cooperate and combine their scientific efforts on the same experimental system. Furthermore, this FACE apparatus utilizes a novel technology, originally developed by Italian institutions, based on the release into the atmosphere, at sonic velocity, of pure CO2 instead of an air-CO2 Mixture. The research activities conducted at the POPFACE site, on the responses of the tree plantation to future atmospheric conditions, have integrated observations at the leaf level, such as photosynthesis, respiration and transpiration, with measures carried out at the whole-tree and stand scale, such as canopy architecture, light interception and biomass production. Finally, the ecosystem dimension has also been analysed by studying root productivity and soil processes, host-parasite interactions, and carbon sequestration throughout a rotation. cycle of the stand.
    Global change alters the stability of food webs
    Emmerson, M. ; Bezemer, T.M. ; Hunter, M.D. ; Jones, T.H. - \ 2005
    Global Change Biology 11 (2005)3. - ISSN 1354-1013 - p. 490 - 501.
    elevated atmospheric co2 - insect herbivore interactions - capita interaction strength - carbon-dioxide atmospheres - prey body-size - primary productivity - ecosystem services - real ecosystems - deciduous trees - plant-growth
    Recent research has generally shown that a small change in the number of species in a food web can have consequences both for community structure and ecosystem processes. However `change¿ is not limited to just the number of species in a community, but might include an alteration to such properties as precipitation, nutrient cycling and temperature. How such changes might affect species interactions is important, not just through the presence or absence of interactions, but also because the patterning of interaction strengths among species is intimately associated with community stability. Interaction strengths encompass such properties as feeding rates and assimilation efficiencies, and encapsulate functionally important information with regard to ecosystem processes. Interaction strengths represent the pathways and transfer of energy through an ecosystem. We review the best empirical data available detailing the frequency distribution of interaction strengths in communities. We present the underlying (but consistent) pattern of species interactions and discuss the implications of this patterning. We then examine how such a basic pattern might be affected given various scenarios of `change¿ and discuss the consequences for community stability and ecosystem functioning. Keywords: community; ecosystems; food webs; herbivore; persistence; plant; predators; prey; resilience; stability
    Net carbon storage in a popular plantation (POPFACE) after three years of free-air CO2 enrichment
    Gielen, B. ; Calfapietra, C. ; Lukac, M. ; Wittig, V.E. ; Angelis, P. de; Janssens, I.A. ; Moscatelli, M.C. ; Grego, S. ; Cotrufo, M.F. ; Godbold, D. ; Hoosbeek, M.R. ; Long, S. ; Miglietta, F. ; Polle, A. ; Bernacchi, C. ; Davey, P.A. ; Ceulemans, R. ; Scarascia-Mugnozza, G. - \ 2005
    Tree Physiology 25 (2005)11. - ISSN 0829-318X - p. 1399 - 1408.
    temperature response functions - elevated atmospheric co2 - soil organic-matter - limited photosynthesis - dioxide enrichment - microbial biomass - turnover - forest - populus - dynamics
    A high-density plantation of three genotypes of Populus was exposed to an elevated concentration of carbon dioxide ([CO2]; 550 µmol mol¿1) from planting through canopy closure using a free-air CO2 enrichment (FACE) technique. The FACE treatment stimulated gross primary productivity by 22 and 11% in the second and third years, respectively. Partitioning of extra carbon (C) among C pools of different turnover rates is of critical interest; thus, we calculated net ecosystem productivity (NEP) to determine whether elevated atmospheric [CO2] will enhance net plantation C storage capacity. Free-air CO2 enrichment increased net primary productivity (NPP) of all genotypes by 21% in the second year and by 26% in the third year, mainly because of an increase in the size of C pools with relatively slow turnover rates (i.e., wood). In all genotypes in the FACE treatment, more new soil C was added to the total soil C pool compared with the control treatment. However, more old soil C loss was observed in the FACE treatment compared with the control treatment, possibly due to a priming effect from newly incorporated root litter. FACE did not significantly increase NEP, probably as a result of this priming effect.
    How does global change affect the strength of trophic interactions?
    Emmerson, M. ; Bezemer, T.M. ; Hunter, M.D. ; Jones, T.H. ; Masters, G.J. ; Dam, N.M. van - \ 2004
    Basic and Applied Ecology 5 (2004)6. - ISSN 1439-1791 - p. 505 - 514.
    insect herbivore interactions - capita interaction strength - elevated atmospheric co2 - real ecosystems - food webs - stability - responses - predator - environments - productivity
    Recent research has generally shown that a small change in the number of species in a food web can have consequences both for community structure and ecosystem processes. However `change` is not limited to just the number of species in a community, but might include an alteration to such properties as precipitation, nutrient cycling and temperature, all of which are correlated with productivity. Here we argue that predicted scenarios of global change will result in increased plant productivity. We model three scenarios of change using simple Lotka-Volterra dynamics, which explore how a global change in productivity might affect the strength of local species interactions and detail the consequences for community and ecosystem level stability. Our results indicate that (i) at local scales the average population size of consumers may decline because of poor quality food resources, (ii) that the strength of species interactions at equilibrium may become weaker because of reduced population size, and (iii) that species populations may become more variable and may take longer to recover from environmental or anthropogenic disturbances. At local scales interaction strengths encompass such properties as feeding rates and assimilation efficiencies, and encapsulate functionally important information with regard to ecosystem processes. Interaction strengths represent the pathways and transfer of energy through an ecosystem. We examine how such local patterns might be affected given various scenarios of `global change` and discuss the consequences for community stability and ecosystem functioning.
    More new carbon in the mineral soil of a poplar plantation under Free Air Carbon Erichment (POPFACE): Cause of increased priming effect?
    Hoosbeek, M.R. ; Lukac, M. ; Dam, D. ; Godbold, D. ; Velthorst, E.J. ; Bondi, F.A. ; Peressotti, A. ; Cotrufo, M.F. ; Angelis, P. de; Scarascia-Mugnozza, G. - \ 2004
    Global Biogeochemical Cycles 18 (2004)1. - ISSN 0886-6236 - 7 p.
    elevated atmospheric co2 - organic-matter - terrestrial ecosystems - turnover - forest - storage - system - decomposition - mechanisms - feedbacks
    [1] In order to establish suitability of forest ecosystems for long-term storage of C, it is necessary to characterize the effects of predicted increased atmospheric CO2 levels on the pools and fluxes of C within these systems. Since most C held in terrestrial ecosystems is in the soil, we assessed the influence of Free Air Carbon Enrichment (FACE) treatment on the total soil C content (C-total) and incorporation of litter derived C (C-new) into soil organic matter (SOM) in a fast growing poplar plantation. C-new was estimated by the C3/C4 stable isotope method. C-total contents increased under control and FACE respectively by 12 and 3%, i.e., 484 and 107 gC/m(2), while 704 and 926 gC/m(2) of new carbon was sequestered under control and FACE during the experiment. We conclude that FACE suppressed the increase of C-total and simultaneously increased C-new. We hypothesize that these opposite effects may be caused by a priming effect of the newly incorporated litter, where priming effect is defined as the stimulation of SOM decomposition caused by the addition of labile substrates.
    How litter quality affects mass loss and N loss from decomposing Sphagnum
    Limpens, J. ; Berendse, F. - \ 2003
    Oikos 103 (2003)3. - ISSN 0030-1299 - p. 537 - 547.
    increased nitrogen deposition - elevated atmospheric co2 - swedish raised bog - vascular plants - heathland ecosystems - northern peatlands - potential decay - central alberta - carbon-dioxide - growth
    Nitrogen (N) deposition may affect litter decomposition and may thus have an impact on the rate of carbon (C) sequestration in Sphagnum peatlands. We present results from four separate experiments aimed at delineating the effects of litter N-enrichment, Sphagnum species, stem part of Sphagnum, and place of incubation on decomposition rate and N release. We measured mass loss and N loss from litterbags incubated at 10-15 cm in the field for one year. Mass loss was positively related to the N/C quotient of the litter, but depended strongly on the range in N/C quotients observed; only a distinct difference in N/C quotients affected mass loss. Although hummock species decayed at a slower rate than hollow species, the differences between the species became less pronounced for old stem parts and for N-enriched litter. Old stem parts decayed at a slower rate than young stem parts, except for S. papillosum. Neither position of incubation (low hummock or hollow), nor the inorganic N concentration of the incubation environment affected mass loss. N loss was mainly determined by, and positively related to, the N/C quotient of the litter; species and stem part had minor effects. Above a N/C quotient of about 0.015, net N loss was observed for all species. We conclude that decomposition of Sphagnum is stimulated by N deposition. As the latter also affects litter N concentration and thus N release, we think that positive feedbacks through changing litter quality should be taken into account when modelling the effects of N deposition on Sphagnum peatlands and C sequestration in these systems.
    Free-air CO2 enrichment (FACE) enhances biomass production in a short-rotation poplar plantation
    Calfapietra, C. ; Gielen, B. ; Galema, A.N.J. ; Lukac, M. ; Angelis, P. de; Moscatelli, M.C. ; Ceulemans, R. ; Scarascia-Mugnozza, G. - \ 2003
    Tree Physiology 23 (2003). - ISSN 0829-318X - p. 805 - 814.
    elevated atmospheric co2 - carbon-dioxide enrichment - net primary production - light-use efficiency - soil n-availability - hybrid poplar - populus-grandidentata - crown architecture - pinus-sylvestris - fine roots
    This paper investigates the possible contribution of Short Rotation Cultures (SRC) to carbon sequestration in both current and elevated atmospheric CO2 concentrations ([CO2]). A dense poplar plantation (1 x 1 m) was exposed to a [CO2] of 550 ppm in Central Italy using the free-air CO2 enrichment (FACE) technique. Three species of Populus were examined, namely P. alba L., P. nigra L. and P. x euramericana Dode (Guinier). Aboveground woody biomass of trees exposed to elevated [CO2] for three growing seasons increased by 15 to 27%, depending on species. As a result, light-use efficiency increased. Aboveground biomass allocation was unaffected, and belowground biomass also increased under elevated [CO2] conditions, by 22 to 38%. Populus nigra, with total biomass equal to 62.02 and 72.03 Mg ha(-1) in ambient and elevated [CO2], respectively, was the most productive species, although its productivity was stimulated least by atmospheric CO2 enrichment. There was greater depletion of inorganic nitrogen from the soil after three growing seasons in elevated [CO2], but no effect of [CO2] on stem wood density, which differed significantly only among species.
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