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Trophic interactions decouple soil carbon temperature response from that of microbial decomposers
  • Benjamin Sulman,
  • Jean P Gibert
Benjamin Sulman
Oak Ridge National Laboratory

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Jean P Gibert
Duke University
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Soil organic carbon (SOC) stocks represent a large component of the global carbon cycle that is sensitive to warming. Modeling and empirical studies often assume that temperature responses of microbial physiological functions and extracellular enzymatic reactions are predictive of ecosystem-scale SOC decomposition responses to warming. However, temperature-dependent soil trophic interactions such as predation of microbial decomposers by other organisms have not yet been incorporated into quantitative SOC models. Here, we incorporated a microbial predator into a tri-trophic population ecology model and a global-scale predictive SOC model to determine how predation would affect soil community population dynamics and temperature sensitivity of SOC stocks. Predators increased SOC stocks and their dependence on substrate input rates. Top-down controls of predators on microbial biomass caused SOC warming responses to diverge from microbial temperature responses, with warming-induced SOC losses reduced or reversed when predators were more temperature-sensitive. Our results suggest that higher trophic levels can reduce the sensitivity of SOC to warming, and that differences in temperature sensitivity across trophic levels may be a key determinant of SOC warming responses.