A Process-Based Experimental Framework for Simulating Soil Organic Carbon Dynamics and Evaluating the Sustainability of Land Management Practices in Intensively Managed Landscapes

摘要

Changes in land cover can significantly affect the spatial and temporal heterogeneity of water-driven soil erosion and deposition in Intensively Managed Landscapes (IMLs), and hence the redistribution of soil organic carbon (SOC) along a hillslope. In IMLs, erosion and deposition are typically more prominent than in grassland and forested ecosystems, while exhibiting higher spatial heterogeneity and temporal variability due to the intensive management. However, the degree to which erosion and deposition affect the carbon budget is not fully understood, and in many cases, it is unclear whether or not these processes lead to net carbon emissions or sequestration. This is, in part, due to the lack of a comprehensive model that accounts for many key processes at the landscape scale. A framework that adequately accounts for such landscape processes would significantly improve model predictions of carbon fluxes and lead to a better understanding of the role of soil redistribution on carbon fluxes. Such a framework would also produce comprehensive carbon budgets that shed light on the sustainability of different management practices in IMLs. Initial steps have been taken to account for the increased role of erosion and deposition on SOC redistribution through the coupling of soil biogeochemical models, like CENTURY, and process-based, upland erosion models, like the Water Erosion Prediction Project (WEPP). The coupled WEPP-CENTURY model will serve as an effective tool for managing and evaluating best management practices that can conserve and replenish SOC. One limitation of this model, however, is the inability to determine the fate of SOC during transport. In this study, changes in SOC in soil aggregates were explored through their interaction with rainfall and runoff and quantified via enrichment ratio and aggregate stability experiments. Soil aggregates encapsulate SOC and act as either sinks of carbon or sources to the atmopshere, so the fate of aggregates during transport greatly impacts the SOC budget. These experiments were performed under different management practices in the Clear Creek, IA watershed, an intensively managed landscape of the U.S. Midwest. The results herein show differences in the stability of aggregates and enrichment ratios for the different management practices in Clear Creek.