Modeling the influence of soil-plant residue contact on carbon mineralization: Comparison of a compartmental approach and a 3D spatial approach

The contact between soil and plant residues has a major effect on the fate of carbon in soil. In this study, we used published data on soil and plant residue incubations. Results showed that larger residues decomposed more slowly because it provides less surface area in contact with the soil. We tested two models with these data. The first was a simple C–N compartmental model with no spatial dimension, in which the contact factor is a multiplicative function of the decomposition constant. The second was an individual-based model that explicitly describes the 3D distribution of organic matter, microbial biomass and inorganic N and their spatial interactions. In this model, we hypothesized that each soil aggregate was a microbial habitat. Both models gave simulated results close to the data. The second, without fitting, reproduced similar results to the empirical macroscopic parameter of the first and indicated that the slower decomposition rate of larger residues was partly because less inorganic nitrogen was available to microorganisms.