Integrating Microbial Community Composition With Biogeochemical Carbon and Nitrogen Dynamics: Examples From Lignin and Polyphenol Decomposition

Biogeochemical models conceptually utilize box and arrow diagrams to explain the rates of carbon cycling in soil. Within these models, labile, intermediate, and recalcitrant pools of carbon are linked to each other, to respiration, and dissolved organic carbon (DOC) flux using parameterized rate functions. These models have often been successful at predicting carbon cycling rates, but they often have to be parameterized to new environmental conditions. This may occur in part because biogeochemical models do not explicitly include the underlying biological mechanisms controlling decomposition. Biogeochemical models may be improved by advances in our understanding the distribution, biomass, and activity of decomposer functional groups. It is especially useful to understand the dynamics of decomposer functional groups and enzyme systems that breakdown recalcitrant soil carbon such as lignin and condensed polyphenolics. Quantitative PCR (QPCR) is an advance in molecular biology that can target decomposer functional groups and functional genes that holds promise for understanding the landscape-level variability in microbial communities controlling the flow and fate of carbon. Here we provide examples of how the abundance and distribution of soil fungi in grassland, temperate and boreal forests predicts the enzymatic capacity of the soil community to decompose recalcitrant soil C. Moreover, the abundance of soil fungi has important implications for the response of decomposers to soil N availability.