المؤلفون: Crowther, TW, Todd-Brown, KEO, Rowe, CW, Wieder, WR, Carey, JC, Machmuller, MB, Snoek, BL, Fang, S, Zhou, G, Allison, SD, Blair, JM, Bridgham, SD, Burton, AJ, Carrillo, Y, Reich, PB, Clark, JS, Classen, AT, Dijkstra, FA, Elberling, B, Emmett, BA, Estiarte, M, Frey, SD, Guo, J, Harte, J, Jiang, L, Johnson, BR, Kröel-Dulay, G, Larsen, KS, Laudon, H, Lavallee, JM, Luo, Y, Lupascu, M, Ma, LN, Marhan, S, Michelsen, A, Mohan, J, Niu, S, Pendall, E, Peñuelas, J, Pfeifer-Meister, L, Poll, C, Reinsch, S, Reynolds, LL, Schmidt, IK, Sistla, S, Sokol, NW, Templer, PH, Treseder, KK, Welker, JM, Bradford, MA

المصدر: Nature. 540(7631)

مصطلحات موضوعية: Carbon, Soil, Models, Statistical, Reproducibility of Results, Ecosystem, Temperature, Atmosphere, Geography, Feedback, Databases, Factual, Global Warming, Carbon Cycle, Models, Statistical, Databases, Factual, General Science & Technology

الوصف: The majority of the Earth's terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances carbon fluxes to and from the soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon-climate feedback that could accelerate climate change.

وصف الملف: application/pdf

URL الوصول: https://escholarship.org/uc/item/2jd320d9

المؤلفون: Luo, Y, Ahlström, A, Allison, SD, Batjes, NH, Brovkin, V, Carvalhais, N, Chappell, A, Ciais, P, Davidson, EA, Finzi, A, Georgiou, K, Guenet, B, Hararuk, O, Harden, JW, He, Y, Hopkins, F, Jiang, L, Koven, C, Jackson, RB, Jones, CD, Lara, MJ, Liang, J, McGuire, AD, Parton, W, Peng, C, Randerson, JT, Salazar, A, Sierra, CA, Smith, MJ, Tian, H, Todd-Brown, KEO, Torn, M, Van Groenigen, KJ, Wang, YP, West, TO, Wei, Y, Wieder, WR, Xia, J, Xu, X, Zhou, T

المصدر: Global Biogeochemical Cycles. 30(1)

مصطلحات موضوعية: Meteorology & Atmospheric Sciences, Atmospheric Sciences, Geochemistry, Oceanography

الوصف: Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.

وصف الملف: application/pdf

URL الوصول: https://escholarship.org/uc/item/1pw7g2r2

المؤلفون: Peter J. Jacobson, Sarah E. Evans, Todd-Brown Keo, Kathryn M. Jacobson

مصطلحات موضوعية: Substrate type, geography, geography.geographical_feature_category, Moisture, Humidity, Environmental science, Dew, Atmospheric sciences, Arid, Grassland, Carbon flux, High humidity

الوصف: Models assume that rainfall is the major source of moisture driving decomposition. Non-rainfall moisture (NRM: high humidity, dew, and fog) can also induce standing litter decomposition, but there have been few standard measurements of NRM-mediated decompositions across sites, and no efforts to extrapolate the contribution of NRM to larger scales to assess whether this mechanism can improve model predictions. Here we show that NRM is an important, year-round source of moisture in grassland sites with contrasting moisture regimes using field measurements and modeling. We first characterized NRM frequency and measured NRM-mediated decomposition in sites on the extreme dry and wet end of grassland systems: at two sites in the Namib Desert, Namibia (hyperarid desert) and at one site in Iowa, USA (tallgrass prairie). NRM was frequent at all sites (85-99% of hours that litter was likely to be wet were attributed to NRM) and tended to occur in cool, high-humidity periods for several hours or more at a time. NRM also caused respiration of standing litter at all sites when litter became sufficiently wet (>5% for fine litter and >13% for coarse), and contributed to mass loss, even in the Namib West site that had almost no rain. When we modeled annual mass loss induced by NRM and rain, and extrapolated our characterization of NRM decomposition to a final site with intermediate rainfall (Sevilleta, New Mexico, semiarid grassland), we found that models driven by rainfall alone underestimated mass loss, while including NRM produced estimates within the range of observed mass loss. Together these findings suggest that NRM is an important missing component in quantitative and conceptual models of litter decomposition, but there is nuance involved in modeling NRM at larger scales. Specifically, temperature and physical features of the substrate emerge as factors that affect the common microbial response to litter wetting under NRM across grasslands sites, and require further study. Hourly humidity can provide an adequate proxy of NRM frequency, but site-specific calibration with litter wetness is needed to accurately attribute decomposition to periods when NRM wets litter. Greater recognition of NRM-driven decomposition and its interaction with other processes (e.g. photodegradation) is needed, especially since fog, dew, and humidity are likely to shift under future climates.Manuscript highlightsNon-rainfall moisture (NRM; humidity, fog, dew) induces decomposition in grasslandsNRM decomposition depends on substrate type, and occurs at colder times than rainIncluding NRM (instead of rain alone) improved predictions of litter decomposition

URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::59fe0375a60c5a29be2804d377a30bb7
https://doi.org/10.1101/696666

المؤلفون: Vahsen ML; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA., Blum MJ; Department of Ecology & Evolutionary Biology, University of Tennessee, Knoxville, TN, USA., Megonigal JP; Smithsonian Environmental Research Center, Edgewater, MD, USA., Emrich SJ; Department of Ecology & Evolutionary Biology, University of Tennessee, Knoxville, TN, USA.; Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA., Holmquist JR; Smithsonian Environmental Research Center, Edgewater, MD, USA., Stiller B; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA., Todd-Brown KEO; Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL, USA., McLachlan JS; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.

المصدر: Science (New York, N.Y.) [Science] 2023 Jan 27; Vol. 379 (6630), pp. 393-398. Date of Electronic Publication: 2023 Jan 26.

نوع المنشور: Journal Article

بيانات الدورية: Publisher: American Association for the Advancement of Science Country of Publication: United States NLM ID: 0404511 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1095-9203 (Electronic) Linking ISSN: 00368075 NLM ISO Abbreviation: Science Subsets: MEDLINE

مواضيع طبية MeSH: Plants*/genetics , Sea Level Rise* , Wetlands*, Soil

مستخلص: Rapid evolution remains a largely unrecognized factor in models that forecast the fate of ecosystems under scenarios of global change. In this work, we quantified the roles of heritable variation in plant traits and of trait evolution in explaining variability in forecasts of the state of coastal wetland ecosystems. A common garden study of genotypes of the dominant sedge Schoenoplectus americanus , "resurrected" from time-stratified seed banks, revealed that heritable variation and evolution explained key ecosystem attributes such as the allocation and distribution of belowground biomass. Incorporating heritable trait variation and evolution into an ecosystem model altered predictions of carbon accumulation and soil surface accretion (a determinant of marsh resilience to sea level rise), demonstrating the importance of accounting for evolutionary processes when forecasting ecosystem dynamics.

المؤلفون: Bailey VL; Pacific Northwest National Laboratory, Richland, WA, USA., Bond-Lamberty B; Pacific Northwest National Laboratory, Joint Global Change Research Institute, University of Maryland, College Park, MD, USA., DeAngelis K; Department of Microbiology, University of Massachusetts Amherst, Amherst, MA, USA., Grandy AS; Department of Natural Resources and Environment, University of New Hampshire, Durham, NH, USA., Hawkes CV; Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA., Heckman K; Northern Research Station, USDA Forest Service, Houghton, MI, USA., Lajtha K; Department of Crop and Soil Sciences, Oregon State University, Corvallis, OR, USA., Phillips RP; Department of Biology, Indiana University Bloomington, Bloomington, IN, USA., Sulman BN; Program in Atmospheric and Oceanic Sciences, Department of Geosciences, Princeton University, Princeton, NJ, USA., Todd-Brown KEO; Pacific Northwest National Laboratory, Richland, WA, USA., Wallenstein MD; Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, USA.

المصدر: Global change biology [Glob Chang Biol] 2018 Mar; Vol. 24 (3), pp. 895-905. Date of Electronic Publication: 2017 Nov 13.

نوع المنشور: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

بيانات الدورية: Publisher: Blackwell Pub Country of Publication: England NLM ID: 9888746 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1365-2486 (Electronic) Linking ISSN: 13541013 NLM ISO Abbreviation: Glob Chang Biol Subsets: MEDLINE

مواضيع طبية MeSH: Carbon Cycle* , Climate Change*, Carbon/*chemistry , Soil/*chemistry, Carbon/metabolism ; Models, Theoretical ; Soil Microbiology

مستخلص: The complexity of processes and interactions that drive soil C dynamics necessitate the use of proxy variables to represent soil characteristics that cannot be directly measured (correlative proxies), or that aggregate information about multiple soil characteristics into one variable (integrative proxies). These proxies have proven useful for understanding the soil C cycle, which is highly variable in both space and time, and are now being used to make predictions of the fate and persistence of C under future climate scenarios. However, the C pools and processes that proxies represent must be thoughtfully considered in order to minimize uncertainties in empirical understanding. This is necessary to capture the full value of a proxy in model parameters and in model outcomes. Here, we provide specific examples of proxy variables that could improve decision-making, and modeling skill, while also encouraging continued work on their mechanistic underpinnings. We explore the use of three common soil proxies used to study soil C cycling: metabolic quotient, clay content, and physical fractionation. We also consider how emerging data types, such as genome-sequence data, can serve as proxies for microbial community activities. By examining some broad assumptions in soil C cycling with the proxies already in use, we can develop new hypotheses and specify criteria for new and needed proxies.
(© 2017 John Wiley & Sons Ltd.)