Observational and experimental constraints on global scale microbial models to improve climate prediction

Background/Question/Methods

Mesocosm-based incubation decomposition experiments using radio-labeled substrates have proved to be a useful source of data for constraining global-scale litter-soil biogeochemistry model structure and for deriving model parameters.  Field based decomposition experiments have provided further constraints and opportunities for independent evaluation of such models. A new generation of process knowledge regarding microbial communities, their actions in litter and soil, and controls on microbial activity from thermal, hydrologic, mineralogical, and biotic interactions with other microbes and with plants has emerged since the models currently deployed in global climate prediction frameworks were developed. We are developing a new generation of microbial modeling capability with the land component of a global coupled Earth system model, for the purpose of improved prediction of greenhouse gas budgets, plant-microbe interactions, and long-term dynamics of carbon and nutrients in plant-litter-soil systems.

Results/Conclusions

We have integrated a detailed belowground reactive transport model within the Community Land Model (CLM), and have added a broad range of litter and soil biogeochemical reactions to the reaction network. We have also integrated a new model of microbial dynamics that considers bacterial and fungal populations as separate and interacting communities. We have introduced a detailed representation of methane cycling, and expanded an existing capability for carbon-nitrogen cycle coupling to include carbon-nitrogen-phosphorus interactions.  We are currently designing new incubation experiments that would allow for the rigorous definition of model reaction network structure and would also provide a basis for reaction network parameterizations. Global-scale results from our new model show that structural choices have an important impact on the timing, magnitude, and sign of global-scale biogeochemistry feedbacks.