Temporal soil enzyme patterns provide new insights into the nutrient economy of acidic hardwood forests

Ecosystem nutrient economies are commonly studied from the perspective of primary productivity in relation to nutrient availability, but a plant-specific view limits our ability to predict broader-scale patterns related to nutrient economics, such as ecosystem carbon turnover and storage controlled by soil microbial communities. Viewing nutrient economics from the heterotrophic decomposer community perspective can provide an additional perspective on ecosystem nutrient economics. We used microbial investment in extracellular enzyme production and ecoenzymatic stoichiometry theory as a conceptual framework to study nutrient economics in forest soils of the Northeast United States. Two years after experimentally increasing soil pH and phosphorus availability to offset the effects of chronic acid and nitrogen deposition, we found that belowground microbial communities were consistently investing more energy into phosphorus acquisition relative to nitrogen, in both space and time, suggesting that ecosystem demand for phosphorus might be high relative to nitrogen. Moreover, soil age and weathering, quantified by comparing glaciated vs non-glaciated regions, might not be useful predictors of nutrient economics in these forest systems. This study offers important insight into controls on ecosystem nutrient dynamics and soil microbial resource investment, information that can inform efforts to model soil microbial interactions and ecosystem carbon dynamics.