Simulation of soil thickness evolution in a complex agricultural landscape at fine spatial and temporal scales

Abstract

Hedgerow networks in the landscape are adapted objects that can be used to study soil redistribution processes within the landscape. In hedged landscapes, water erosion redistributes soil, but hedges act as barriers to the physical transfers of soil particles. The most systematic effect is the increase in the thickness of A-horizons uphill from the hedges. A field experiment was carried out within an old agricultural area with a high density of hedges. A high resolution digital elevation model and a soil thickness map were created to investigate the effect of hedges on soil reorganization. The aims of this paper are to use this pedological knowledge for a better understanding of process dynamics, to simulate quantitatively the effect of hedgerow network on soil organization and redistribution, and to test different scenarios of land management on soil redistribution dynamics. The simulation uses a mechanistic model where the change in soil thickness over time depends on the transport of soil through a diffusive transport and a water erosion process. We tested the suitability of the model to operate on a DEM with grid size of 1 m and a simulation time of less than 1200 years. We performed the simulations on theoretical and actual DEMs with and without the hedgerow network. The effect of different land use and management scenarios on soil redistribution was tested. Those scenarios were applied on a DEM of real landscape, with the addition and removal of hedge on the DEM. The results suggest that the combination of diffusive transport and water erosion could significantly modify the topography and soil redistribution over a few centuries. The simulations show that hedges modify soil distribution and landforms by favouring deposition in the uphill position and soil erosion in the downhill position in agreement with field observations.