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【Nature 等】补偿性水效应联系温度与全球陆地碳汇年际变化 等
发布时间:2017-02-14  来源:土壤与农业可持续发展国家重点实验室  浏览:310

【土壤微生物群落与麋鹿觅食强度】Lauren C. Cline1,*, Donald R. Zak2,3, Rima A. Upchurch2, Zachary B. Freedman4 and Anna R. Peschel5. Soil microbial communities and elk foraging intensity: implications for soil biogeochemical cycling in the sagebrush steppe. Ecology Letters Volume 20, Issue 2, pages 202–211, February 2017

Abstract

Foraging intensity of large herbivores may exert an indirect top-down ecological force on soil microbial communities via changes in plant litter inputs. We investigated the responses of the soil microbial community to elk (Cervus elaphus) winter range occupancy across a long-term foraging exclusion experiment in the sagebrush steppe of the North American Rocky Mountains, combining phylogenetic analysis of fungi and bacteria with shotgun metagenomics and extracellular enzyme assays. Winter foraging intensity was associated with reduced bacterial richness and increasingly distinct bacterial communities. Although fungal communities did not respond linearly to foraging intensity, a greater β-diversity response to winter foraging exclusion was observed. Furthermore, winter foraging exclusion increased soil cellulolytic and hemicellulolytic enzyme potential and higher foraging intensity reduced chitinolytic gene abundance. Thus, future changes in winter range occupancy may shape biogeochemical processes via shifts in microbial communities and subsequent changes to their physiological capacities to cycle soil C and N.


【土壤生物地球化学循环】Robert W. Buchkowski1,*, Mark A. Bradford1, Andrew Stuart Grandy2, Oswald J. Schmitz1 and William R. Wieder3,4. Applying population and community ecology theory to advance understanding of belowground biogeochemistry. Ecology Letters Volume 20, Issue 2, pages 231–245, February 2017

 

Abstract

Approaches to quantifying and predicting soil biogeochemical cycles mostly consider microbial biomass and community composition as products of the abiotic environment. Current numerical approaches then primarily emphasise the importance of microbe–environment interactions and physiology as controls on biogeochemical cycles. Decidedly less attention has been paid to understanding control exerted by community dynamics and biotic interactions. Yet a rich literature of theoretical and empirical contributions highlights the importance of considering how variation in microbial population ecology, especially biotic interactions, is related to variation in key biogeochemical processes like soil carbon formation. We demonstrate how a population and community ecology perspective can be used to (1) understand the impact of microbial communities on biogeochemical cycles and (2) reframe current theory and models to include more detailed microbial ecology. Through a series of simulations we illustrate how density dependence and key biotic interactions, such as competition and predation, can determine the degree to which microbes regulate soil biogeochemical cycles. The ecological perspective and model simulations we present lay the foundation for developing empirical research and complementary models that explore the diversity of ecological mechanisms that operate in microbial communities to regulate biogeochemical processes.


【土地利用变化引起的历史二氧化碳变化】A. Arneth, S. Sitch, J. Pongratz, B. D. Stocker, P. Ciais, B. Poulter, A. D. Bayer, A. Bondeau, L. Calle, L. P. Chini, T. Gasser, M. Fader, P. Friedlingstein, E. Kato, W. Li, M. Lindeskog, J. E. M. S. Nabel, T. A. M. Pugh, E. Robertson, N. Viovy, C. Yue & S. Zaehle. Historical carbon dioxide emissions caused by land-use changes are possibly larger than assumed. Nature Geoscience 10, 79–84 (2017) doi:10.1038/ngeo2882

Abstract

The terrestrial biosphere absorbs about 20% of fossil-fuel CO2 emissions. The overall magnitude of this sink is constrained by the difference between emissions, the rate of increase in atmospheric CO2 concentrations, and the ocean sink. However, the land sink is actually composed of two largely counteracting fluxes that are poorly quantified: fluxes from land-use change and CO2 uptake by terrestrial ecosystems. Dynamic global vegetation model simulations suggest that CO2 emissions from land-use change have been substantially underestimated because processes such as tree harvesting and land clearing from shifting cultivation have not been considered. As the overall terrestrial sink is constrained, a larger net flux as a result of land-use change implies that terrestrial uptake of CO2 is also larger, and that terrestrial ecosystems might have greater potential to sequester carbon in the future. Consequently, reforestation projects and efforts to avoid further deforestation could represent important mitigation pathways, with co-benefits for biodiversity. It is unclear whether a larger land carbon sink can be reconciled with our current understanding of terrestrial carbon cycling. Our possible underestimation of the historical residual terrestrial carbon sink adds further uncertainty to our capacity to predict the future of terrestrial carbon uptake and losses.


【表层土壤水分的全球分布与动态】Kaighin A. McColl, Seyed Hamed Alemohammad, Ruzbeh Akbar, Alexandra G. Konings, Simon Yueh & Dara Entekhabi. The global distribution and dynamics of surface soil moisture. Nature Geoscience 10, 100–104 (2017) doi:10.1038/ngeo2868

Abstract

Surface soil moisture has a direct impact on food security, human health and ecosystem function. It also plays a key role in the climate system, and the development and persistence of extreme weather events such as droughts, floods and heatwaves. However, sparse and uneven observations have made it difficult to quantify the global distribution and dynamics of surface soil moisture. Here we introduce a metric of soil moisture memory and use a full year of global observations from NASA’s Soil Moisture Active Passive mission to show that surface soil moisture—a storage believed to make up less than 0.001% of the global freshwater budget by volume, and equivalent to an, on average, 8-mm thin layer of water covering all land surfaces—plays a significant role in the water cycle. Specifically, we find that surface soil moisture retains a median 14% of precipitation falling on land after three days. Furthermore, the retained fraction of the surface soil moisture storage after three days is highest over arid regions, and in regions where drainage to groundwater storage is lowest. We conclude that lower groundwater storage in these regions is due not only to lower precipitation, but also to the complex partitioning of the water cycle by the surface soil moisture storage layer at the land surface.


【极端气候条件下减少CO2施肥对温带C3草原的影响】W. A. Obermeier, L. W. Lehnert, C. I. Kammann, C. Müller, L. Grünhage, J. Luterbacher, M. Erbs, G. Moser, R. Seibert, N. Yuan & J. Bendix. Reduced CO2 fertilization effect in temperate C3 grasslands under more extreme weather conditions. Nature Climate Change 7, 137–141 (2017) doi:10.1038/nclimate3191

Abstract

The increase in atmospheric greenhouse gas concentrations from anthropogenic activities is the major driver of recent global climate change1. The stimulation of plant photosynthesis due to rising atmospheric carbon dioxide concentrations ([CO2]) is widely assumed to increase the net primary productivity (NPP) of C3 plants—the CO2 fertilization effect (CFE)1, 2, 3, 4, 5, 6, 7. However, the magnitude and persistence of the CFE under future climates, including more frequent weather extremes, are controversial1, 2, 3, 8, 9, 10, 11, 12. Here we use data from 16 years of temperate grassland grown under ‘free-air carbon dioxide enrichment conditions to show that the CFE on above-ground biomass is strongest under local average environmental conditions. The observed CFE was reduced or disappeared under wetter, drier and/or hotter conditions when the forcing variable exceeded its intermediate regime. This is in contrast to predictions of an increased CO2 fertilization effect under drier and warmer conditions13. Such extreme weather conditions are projected to occur more intensely and frequently under future climate scenarios1. Consequently, current biogeochemical models might overestimate the future NPP sink capacity of temperate C3 grasslands and hence underestimate future atmospheric [CO2] increase.


【滨海湿地生态系统】Christopher A. Gabler, Michael J. Osland, James B. Grace, Camille L. Stagg, Richard H. Day, Stephen B. Hartley, Nicholas M. Enwright, Andrew S. From, Meagan L. McCoy & Jennie L. McLeod. Macroclimatic change expected to transform coastal wetland ecosystems this century. Nature Climate Change 7, 142–147 (2017) doi:10.1038/nclimate3203

Abstract

Coastal wetlands, existing at the interface between land and sea, are highly vulnerable to climate change1, 2, 3. Macroclimate (for example, temperature and precipitation regimes) greatly influences coastal wetland ecosystem structure and function4, 5. However, research on climate change impacts in coastal wetlands has concentrated primarily on sea-level rise and largely ignored macroclimatic drivers, despite their power to transform plant community structure6, 7, 8, 9, 10, 11, 12 and modify ecosystem goods and services5, 13. Here, we model wetland plant community structure based on macroclimate using field data collected across broad temperature and precipitation gradients along the northern Gulf of Mexico coast. Our analyses quantify strongly nonlinear temperature thresholds regulating the potential for marsh-to-mangrove conversion. We also identify precipitation thresholds for dominance by various functional groups, including succulent plants and unvegetated mudflats. Macroclimate-driven shifts in foundation plant species abundance will have large effects on certain ecosystem goods and services5, 14, 15, 16. Based on current and projected climatic conditions, we project that transformative ecological changes are probable throughout the region this century, even under conservative climate scenarios. Coastal wetland ecosystems are functionally similar worldwide, so changes in this region are indicative of potential future changes in climatically similar regions globally.


【补偿性水效应联系温度与全球陆地碳汇年际变化】Martin Jung, Markus Reichstein, Christopher R. Schwalm, Chris Huntingford, Stephen Sitch, Anders Ahlström, Almut Arneth, Gustau Camps-Valls, Philippe Ciais, Pierre Friedlingstein, Fabian Gans, Kazuhito Ichii, Atul K. Jain, Etsushi Kato, Dario Papale, Ben Poulter, Botond Raduly, Christian Rödenbeck, Gianluca Tramontana, Nicolas Viovy, Ying-Ping Wang, Ulrich Weber, Sönke Zaehle & Ning Zeng. Compensatory water effects link yearly global land CO2 sink changes to temperature. Nature 541, 516–520 (26 January 2017) doi:10.1038/nature20780

Abstract

Large interannual variations in the measured growth rate of atmospheric carbon dioxide (CO2) originate primarily from fluctuations in carbon uptake by land ecosystems1, 2, 3. It remains uncertain, however, to what extent temperature and water availability control the carbon balance of land ecosystems across spatial and temporal scales3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. Here we use empirical models based on eddy covariance data15 and process-based models16, 17 to investigate the effect of changes in temperature and water availability on gross primary productivity (GPP), terrestrial ecosystem respiration (TER) and net ecosystem exchange (NEE) at local and global scales. We find that water availability is the dominant driver of the local interannual variability in GPP and TER. To a lesser extent this is true also for NEE at the local scale, but when integrated globally, temporal NEE variability is mostly driven by temperature fluctuations. We suggest that this apparent paradox can be explained by two compensatory water effects. Temporal water-driven GPP and TER variations compensate locally, dampening water-driven NEE variability. Spatial water availability anomalies also compensate, leaving a dominant temperature signal in the year-to-year fluctuations of the land carbon sink. These findings help to reconcile seemingly contradictory reports regarding the importance of temperature and water in controlling the interannual variability of the terrestrial carbon balance3, 4, 5, 6, 9, 11, 12, 14. Our study indicates that spatial climate covariation drives the global carbon cycle response.


【海拔改变全球温带林线生态系统性质】Jordan R. Mayor, Nathan J. Sanders, Aimée T. Classen, Richard D. Bardgett, Jean-Christophe Clément, Alex Fajardo, Sandra Lavorel, Maja K. Sundqvist, Michael Bahn, Chelsea Chisholm, Ellen Cieraad, Ze’ev Gedalof, Karl Grigulis, Gaku Kudo, Daniel L. Oberski & David A. Wardle. Elevation alters ecosystem properties across temperate treelines globally. Nature 542, 91–95 (02 February 2017) doi:10.1038/nature21027

Abstract

Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries1, 2. Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics3, 4. Elevational gradients, as thermoclines, also enable prediction of long-term ecological responses to climate warming5, 6, 7. One of the most striking manifestations of increasing elevation is the abrupt transitions from forest to treeless alpine tundra8. However, whether there are globally consistent above- and belowground responses to these transitions remains an open question4. To disentangle the direct and indirect effects of temperature on ecosystem properties, here we evaluate replicate treeline ecotones in seven temperate regions of the world. We find that declining temperatures with increasing elevation did not affect tree leaf nutrient concentrations, but did reduce ground-layer community-weighted plant nitrogen, leading to the strong stoichiometric convergence of ground-layer plant community nitrogen to phosphorus ratios across all regions. Further, elevation-driven changes in plant nutrients were associated with changes in soil organic matter content and quality (carbon to nitrogen ratios) and microbial properties. Combined, our identification of direct and indirect temperature controls over plant communities and soil properties in seven contrasting regions suggests that future warming may disrupt the functional properties of montane ecosystems, particularly where plant community reorganization outpaces treeline advance.


【土壤生态系统结构与土壤碳循环】Elly Morrien et al. Soil networks become more connected and take up more carbon as nature restoration progresses. Nature Communications 8, Article number: 14349 (2017) doi:10.1038/ncomms14349

Abstract

Soil organisms have an important role in aboveground community dynamics and ecosystem functioning in terrestrial ecosystems. However, most studies have considered soil biota as a black box or focussed on specific groups, whereas little is known about entire soil networks. Here we show that during the course of nature restoration on abandoned arable land a compositional shift in soil biota, preceded by tightening of the belowground networks, corresponds with enhanced efficiency of carbon uptake. In mid- and long-term abandoned field soil, carbon uptake by fungi increases without an increase in fungal biomass or shift in bacterial-to-fungal ratio. The implication of our findings is that during nature restoration the efficiency of nutrient cycling and carbon uptake can increase by a shift in fungal composition and/or fungal activity. Therefore, we propose that relationships between soil food web structure and carbon cycling in soils need to be reconsidered.

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