Modeling microbial dynamics and heterotrophic soil respiration: Effect of climate change

Microbial respiration is the largest flux of carbon (C) out of the soil. The responses of microbes to climate change will determine the amplitude of the feedbacks between the carbon cycle and climate. Carbon models linking soil organic carbon turnover and microbial ecophysiology can predict better transient and long-term responses of soil C stocks and respiration to climate change. Yet microbial models are not used in Earth system models. We propose here a roadmap for how to build simple mechanistic microbial carbon models sensitive to climate conditions and provide a toolbox of functions and parameters used in current models. We show that they can predict general empirical patterns of responses to warming and give better predictions of global C stocks. Because there is still a gap to fill in C stock global distributions, we discuss directions to complexify microscale microbial models and the challenges to tackle when scaling them up from the micro- to the macroscale. We aim for this overview to clarify the properties and utilities of microbial models, and to expose the opportunities for future work to better assess the uncertainty of future carbon cycle projections.