Department of Energy • Office of Science • Biological and Environmental Research1 BER Climate Research

Representing Complex Consumer-Substrate Networks: Development for ESM Land Models with an Application to Litter Decomposition

ObjectiveCurrent ESM land models lack mechanistic representation of substrate (e.g., C and N) competition and the resulting decomposition kinetics. Our goals were to develop a new concept for representing these dynamics (using the total quasi-steady state assumption and perturbation theory) in a manner applicable to CLM4.5.

Research• We developed a new formulation for the

competitive environment in which soil organic matter dynamics occur, including interactions between microbial groups, plants, and abiotic factors (e.g., minerals).• We applied the model to a guild-based

microbial litter decomposition experiment and compared to observations and previous methods.

Impacts• We accurately explained lignin

decomposition dynamics with substrate competition between microbial guilds.•Decomposition is co-regulated by both

the litter chemistry and microbial community structure.•We are integrating these developments

in CLM4.5.Reference: Tang, J. Y. and Riley, W. J.: A total quasi-steady-state formulation of substrate uptake kinetics in complex networks and an example application to microbial litter decomposition, Biogeosciences, 10, 8329–8351, 2013, doi:10.5194/bg-10-8329-2013.

Figure. Comparison between model predictions and observations.

Figure. The new substrate kinetics structure.