Assessment of Predictability of Erosion in Intensively Managed Agroecosystems: Implications for sediment transport

In the era of the Anthropocene, organic-rich landscapes of the Upper Midwest in the US previously covered by prairie plants and forests have been ideal candidates for agricultural production and are characterized by increasing adoption rates of agricultural practices and energy inputs, aiming at the short-term maximization of crop productivity. Land use intensification has led to excessive runoff and sediment yields, which are the major contributors to soil and water quality degradation, in addition to adverse effects on ecosystem services. Research in the context of erosion models has been mostly focused on empirical and lumped approaches, while there is lack of fundamental understanding of the physical mechanisms and feedbacks between land use, runoff, and sediment. The goal of the present study is to decipher the role of land use in flow and sediment response. Rainfall simulator experiments were conducted at four contrasting land use types of the Upper Midwest. Flow and sediment time series were obtained at the plot outlets, while flow hydraulics were measured along the plots and throughout the experiments.

Results demonstrate that the feedbacks between land use-induced geomorphic features, flow, and sediment dictate the dominant erosion mechanisms and affect the characteristic timescales of flow and sediment response. Bare settings represent the worst-case scenarios in terms of runoff and sediment fluxes and are characterized by a rainsplash dominated zone and a turbulent rill flow dominated zone. In agroecosystems with ridge tillage, the direction of the oriented roughness plays an important role, either by providing preferential flow pathways or by retarding the flow. The restored prairie landscapes serve as reference comparison sites, having experienced minimal disturbance, and provide insight into the effects of the wake interference roughness regime resulting from the densely packed vegetation elements. The grain stream power concept is borrowed from fluvial geomorphology to predict the erosion rates for contrasting land use settings, as well as develop a taxonomy of erosion mechanisms that explains how these settings have distinct sediment budgets. This study serves as a tool for more accurate prediction of sediment fluxes and identification of erosion hotspots.