Incorporating microbial ecology concepts into global soil mineralization models to improve predictions of carbon and nitrogen fluxes

“Global models of soil carbon (C) and nitrogen (N) fluxes become increasingly needed to describe
climate change impacts, yet they typically have limited ability to reflect microbial activities that may affect
global-scale soil dynamics. Benefiting from recent advances in microbial knowledge, we evaluated critical
assumptions on microbial processes to be applied in global models. We conducted a sensitivity analysis of soil
respiration rates (Cmin) and N mineralization rates (Nmin) for different model structures and parameters
regarding microbial processes and validated them with laboratory incubation data of diverse soils. Predicted
Cmin was sensitive tomicrobial biomass, and themodel fit to observed Cmin improved when using site-specific
microbial biomass. Cmin was less affected by the approach of microbial substrate consumption (i.e., linear,
multiplicative, or Michaelis-Menten kinetics). The sensitivity ofCmin to increasing soil N fertility was idiosyncratic
and depended on the assumed mechanism of microbial C:N stoichiometry effects: a C overflow mechanism
upon N limitation (with decreasedmicrobial growth efficiency) led to the bestmodel fit. Altogether, inclusion of
microbial processes reduced prediction errors by 26% (for Cmin) and 7% (for Nmin) in our validation data set.
Our study identified two important aspects to incorporate into global models: site-specific microbial biomass
and microbial C:N stoichiometry effects. The former requires better understandings of spatial patterns of
microbial biomass and its drivers, while the latter urges for further conceptual progress on C-N interactions.
With such advancements, we envision improved predictions of global C and N fluxes for a current and
projected climate.”
(Citaat: Fujita, Y., Witte, J.P.M., van Bodegom, P.M. Incorporating microbial ecology concepts into global soil mineralization models to improve predictions of carbon and nitrogen fluxes – Global Biogeochemical cycles 28(2014)3, p.223-238 – Open Access)