Impacts of Soil Redistribution on the Landscape and Soil Organic Carbon of the Temperate Prairies Ecoregion of the United States

Increases of global demand for agricultural production and global warming affect fragile lands. Cultivated lands in the United States have been affected by accelerated erosion causing soil organic carbon (SOC) redistribution and other agricultural and environmental problems. For example, the U.S. Temperate Prairies ecoregion (ecoregion 9.2) have been altered by intensive and conventional agricultural practices. This study assessed the impacts of soil and SOC redistribution from water and tillage erosion at local and regional scales. At the local scale, a model framework (USPED +TEP-A) and the LAPSUS model were evaluated using 137Cs information in two agricultural fields. The results showed that the model framework had better agreement statistically and spatially than the LAPSUS model in both fields. Then, the model framework results were used to estimate SOC redistribution. The results showed SOC loss in eroded areas (negative values) and SOC gain (positive values) in deposition areas. At the regional scale, the model framework estimated soil and SOC redistribution during a baseline period (1992- 2005) and a future projected period (2006-2050). The results during the baseline period showed changes in precipitation affected the overall regional erosion amount. Besides, topography also played an important role in soil erosion. The baseline and future projected results provided information about sensitivity and potential effects of climate and land use and land cover changes in soil and SOC redistribution in the ecoregion. These overall regional results helped to identify places with high net soil redistribution rates, and it supported arguments that SOC dynamics and soil erosion are associated, where water and tillage erosion can influence SOC removal in eroded areas, subsequent carbon sequestration in deposition areas, SOC export from the system, and reduce the SOC pool by an increase in the oxidation rate and losses. Hence, this study will be useful to improve information about the spatial distribution of soil redistribution across agricultural landscapes and its impact on the productivity and soil C balance. This may lead to a better understanding of SOC dynamics within soil redistributed areas, to provide assessments of the impact of water and tillage erosion, and to control accelerated erosion in the future