Objective

1. Representing Complex Consumer-Substrate Networks: Development for ESM Land Models with an Application to Litter Decomposition Objective Current 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. Figure. The new substrate kinetics structure. Figure. Comparison between model predictions and observations. • 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.