Comment on egusphere-2022-359

Abstract

Understanding the coupling of nitrogen (N) and carbon (C) cycles of land ecosystems, requires understanding microbial element use efficiencies of soil organic matter (SOM) decomposition. Whereas important controls of those efficiencies by microbial community adaptations have been shown at the scale of a soil pore, a simplified representation of those controls is needed at the ecosystem scale. However, without abstracting from the many details, models are not identifiable, i.e. can not be fitted without ambiguities to observations. There is a need to find, implement, and validate abstract simplified formulations of theses processes. Therefore, we developed the SESAM model as an ab- straction of the more detailed soil enzyme allocation model (SEAM) model and tested, whether it can provide the same decadal-term predictions. SEAM explicitly models community adaptation strategies of resource allocation to extracellular enzymes and enzyme limitations on SOM decomposition. It thus provides a scaling from representing several microbial functional groups to a single holistic microbial community. Here we further abstracted the model using quasi-steady-state assumption for extracellular enzyme pools to derive the SESAM model. SESAM reproduced the priming effect, the SOM banking mechanism, and the damping of fluctuations of carbon use efficiency with microbial competition as predicted by SEAM and other more detailed models. This development is an important step towards more parsimonious representation of soil microbial effects in global land surface models.