Abstract

Soil organic matter (SOM) is a dynamic entity. The amount (stock) of organic matter in a given soil can increase or decrease depending on numerous factors including climate, vegetation type, nutrient availability, disturbance, land use, and management practices. But even when stocks are at equilibrium, SOM is in a continual state of flux; new inputs cycle—via the process of decomposition—into and through organic matter pools of various qualities and replace materials that are either transferred to other pools or mineralized. An understanding of SOM turnover is crucial for quantifying carbon and nutrient cycles and for determining the quantitative and temporal responses of local, regional, or global carbon and nutrient budgets to perturbations caused by human activities or climate change.