Eco-enzymatic stoichiometry and enzymatic vectors reveal differential C, N, P dynamics in decaying litter along a land-use gradient

To evaluate carbon (C), nitrogen (N), and phosphorus (P) dynamics during the decomposition process, we investigated the temporal variability of extracellular enzymatic activities (EEA) associated with C, N, and P acquisition in microbial communities from different land uses. We hypothesized that EEA ratios would reveal different primary resource requirements with respect to microbial demand, depending on soil properties, litter type and the relative proportion of bacteria:fungi in the microbial community. To test this hypothesis, we implemented an experiment using four litters (Triticum aestivum, Fagus sylvatica, Festuca arundinacea and Robinia pseudoacacia) in four soils (cropland, plantation, prairie and forest) located in close proximity to one another on the same parent material. Analyses of EEA showed that overall N requirement increased relative to P during litter decay, but C requirement increased more rapidly than either N or P in most of these ecosystems. Soil type was the main factor controlling N versus P requirement whereas litter type was the primary driver of C versus nutrient requirement. Shifts in EEA were related to changes in metabolic quotient (C respired per unit biomass) but there was no evidence that the relative proportion of fungi:bacteria drove changes in EEA. We concluded that the use of EEA as a proxy of microbial resource demand improved our understanding of temporal shifts in resource requirements to microbial communities, their associated respiration efficiency and dynamics of C and nutrients among different ecosystems.