Redistribution Effects on Changes in Soil Carbon Storage Potential in Intensely Managed Landscapes

摘要

Currently, biogeochemical models lack the ability to simulate accurately soil organic carbon (SOC) dynamics, especially in intensely managed landscapes (IMLs) located throughout much of the U.S. Midwest, as they do not account for lateral and downslope redistribution of soil and SOC. This limitation can increase the uncertainty in predicting SOC sequestration potential (SOC-SP) when quantifying carbon budgets for a landscape. In this study, the limitation was addressed by complementing event-based and seasonal SOC observations for a hillslope within the Clear Creek, IA watershed with the development of a coupled modeling framework focused on SOC redistribution by vertical mixing and downslope/lateral mobilization. The framework links an off-the-shelf, spatially distributed, hillslope erosion model (Water Erosion Prediction Project, WEPP) with a biogeochemical model CENTURY. Specifically, key physical and biogeochemical parameters were monitored throughout several growing seasons, while soil samples were collected along various hillslope positions and measured for SOC. Results show heterogeneous stocks of SOC across the hillslope, with eroding zones having lower SOC concentrations than depositional zones. Accounting for the spatial heterogeneity and temporal variability of SOC within a landscape will lead toward improved SOC-SP predictions as well as the development of more sustainable agricultural practices.