Trophic interactions decouple soil carbon temperature response from that
of microbial decomposers
Abstract
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.