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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 6
Geosci. Model Dev., 8, 1789-1808, 2015
https://doi.org/10.5194/gmd-8-1789-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Geosci. Model Dev., 8, 1789-1808, 2015
https://doi.org/10.5194/gmd-8-1789-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Model description paper 17 Jun 2015

Model description paper | 17 Jun 2015

Representing life in the Earth system with soil microbial functional traits in the MIMICS model

W. R. Wieder1,2, A. S. Grandy3, C. M. Kallenbach3, P. G. Taylor2,4, and G. B. Bonan1 W. R. Wieder et al.
  • 1Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, USA
  • 2Institute for Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
  • 3Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA
  • 4Nicholas School of the Environment, Duke University, Durham, NC, USA

Abstract. Projecting biogeochemical responses to global environmental change requires multi-scaled perspectives that consider organismal diversity, ecosystem processes, and global fluxes. However, microbes, the drivers of soil organic matter decomposition and stabilization, remain notably absent from models used to project carbon (C) cycle–climate feedbacks. We used a microbial trait-based soil C model with two physiologically distinct microbial communities, and evaluate how this model represents soil C storage and response to perturbations. Drawing from the application of functional traits used to model other ecosystems, we incorporate copiotrophic and oligotrophic microbial functional groups in the MIcrobial-MIneral Carbon Stabilization (MIMICS) model; these functional groups are akin to "gleaner" vs. "opportunist" plankton in the ocean, or r- vs. K-strategists in plant and animal communities. Here we compare MIMICS to a conventional soil C model, DAYCENT (the daily time-step version of the CENTURY model), in cross-site comparisons of nitrogen (N) enrichment effects on soil C dynamics. MIMICS more accurately simulates C responses to N enrichment; moreover, it raises important hypotheses involving the roles of substrate availability, community-level enzyme induction, and microbial physiological responses in explaining various soil biogeochemical responses to N enrichment. In global-scale analyses, we show that MIMICS projects much slower rates of soil C accumulation than a conventional soil biogeochemistry in response to increasing C inputs with elevated carbon dioxide (CO2) – a finding that would reduce the size of the land C sink estimated by the Earth system. Our findings illustrate that tradeoffs between theory and utility can be overcome to develop soil biogeochemistry models that evaluate and advance our theoretical understanding of microbial dynamics and soil biogeochemical responses to environmental change.

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Projecting biogeochemical responses to environmental change requires multi-scaled perspectives. However, microbes, the drivers of soil organic matter decomposition and stabilization, remain notably absent from models used to project carbon cycle–climate feedbacks. Here, we apply and evaluate representations of microbial functional diversity across scales and find that such representations may be critical to accurately project soil carbon dynamics in a changing world.
Projecting biogeochemical responses to environmental change requires multi-scaled perspectives....
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