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Simulating Global Terrestrial Carbon and Nitrogen Biogeochemical Cycles with Implicit and Explicit Representations of Soil Microbial Activity
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  • William R Wieder,
  • Melannie Hartman,
  • Emily Kyker-Snowman,
  • Brooke Eastman,
  • Katerina Georgiou,
  • Derek Pierson,
  • Katherine Rocci,
  • stuart grandy
William R Wieder
National Center for Atmospheric Research

Corresponding Author:[email protected]

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Melannie Hartman
Natural Resource Ecology Laboratory
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Emily Kyker-Snowman
University of New Hampshire
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Brooke Eastman
Division of Forestry and Natural Resources, West Virginia University
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Katerina Georgiou
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Derek Pierson
Rocky Mountain Research Station Forest and Woodland Ecosystems
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Katherine Rocci
University of Colorado Boulder
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stuart grandy
University of New Hampshire
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Nutrient limitation is widespread in terrestrial ecosystems. Accordingly, representations of nitrogen (N) limitation in land models typically dampen rates of terrestrial carbon (C) accrual, compared with C-only simulations. These previous findings, however, rely on soil biogeochemical models that implicitly represent microbial activity and physiology. Here we present results from a biogeochemical model testbed that allows us to investigate how an explicit vs. implicit representation of soil microbial activity, as represented in the MIcrobial-MIneral Carbon Stabilization (MIMICS) and Carnegie–Ames–Stanford Approach (CASA) soil biogeochemical models, respectively, influence plant productivity and terrestrial C and N fluxes at initialization and over the historical period. When forced with common boundary conditions, larger soil C pools simulated by the MIMICS model reflect longer inferred soil organic matter (SOM) turnover times than those simulated by CASA. At steady state, terrestrial ecosystems experience greater N limitation when using the MIMICS-CN model, which also increases the inferred SOM turnover time. Over the historical period, however, higher rates of N mineralization were fueled by warming-induced acceleration of SOM decomposition over high latitude ecosystems in the MIMICS-CN simulation reduce this N limitation, resulting in faster rates of vegetation C accrual. Moreover, as SOM stoichiometry is an emergent property of MIMICS-CN, we highlight opportunities to deepen understanding of sources of persistent SOM and explore its potential sensitivity to environmental change. Our findings underscore the need to improve understanding and representation of plant and microbial resource allocation and competition in land models that represent coupled biogeochemical cycles under global change scenarios.
08 Dec 2023Submitted to ESS Open Archive
10 Dec 2023Published in ESS Open Archive