Merging microbial traits and soil physiochemical interactions with the MIMICS (MIcrobial-MIneral Carbon Stabilization) model

Background/Question/Methods

In global land surface models, greater attention has been given to improving ecological representations of the autotrophic, or “green”, carbon (C) cycle, whereas comparatively less attention has been given to revising ecologically driven representations of the soil heterotrophic, or “brown”, C cycle.  A growing body of literature calls for significant revisions to the theoretical basis for modeling soil C dynamics and highlights the need to explicitly simulate the microbial processes responsible for decomposition and stabilization of organic matter.  To more rigorously evaluate dynamics between microbial physiology, soil environmental conditions and soil organic matter (SOM) formation we present the MIMICS (MIcrobial-MIneral Carbon Stabilization) model.  MIMICS is a process-based modeling framework that explores the potential role of microbial physiology and the stabilization of microbial biomass at the soil-mineral interface as key drivers in the formation of SOM. 

Results/Conclusions

We evaluate models based upon theories of chemical recalcitrance vs. microbial control over SOM turnover through their response to global change scenarios. The soil C responses simulated by MIMICS show better agreement with observational data, suggesting that MIMICS marks a notable improvement in the numerical representation of contemporary soil ecological theory.  We highlight key uncertainties in our representation and parameterization of processes relating to microbial physiological traits and soil C – mineral interactions.  Resolving these uncertainties presents unique opportunities to merge experimental and modeling activities that will significantly advance our understanding of the world beneath our feet.