It is well understood that decomposition is largely driven by extracellular enzymes produced by microorganisms, but  traditional decomposition models have included neither microbes nor their enzymes as explicit drivers of decomposition. To date, patterns of leaf litter decay have largely been approximated by empirical relationships that do not include driving mechanisms and thus lack the generality to adequately address perturbations such as N deposition.  Most predictive models of decomposition are driven by initial litter chemistry and environmental conditions , rather than microbial dynamics, and fail to capture impacts arising from “bottom up” changes in microbial community composition or function, that play a critical role in the stabilization of organic matter.  

Results/Conclusions

When enzymes and the groups of microorganisms that produce them, with enzyme activities and affinities for substrates varying by group, are added to decomposition models , several phenomena emerge that qualitatively change the behavior of the models and the conclusions that can be drawn from them. The accuracy of such models is currently limited, however, by the availability of data on microbial enzyme production, enzyme stabilization and loss, as well as reaction product formation and substrate availability. Recent advances in genomics and proteomics have the potential to make a significant contribution toward the creation of decomposition models that include different microbial groups and the enzymes they produce, which in turn will improve our ability to predict decomposition and elucidate the mechanisms controlling C sequestration and loss.