Soil degradation caused by a high-intensity rainfall event: implications for medium-term soil sustainability in Burgundian vineyards.

International audience

English. The purpose of this paper is to provide a sediment-flux quantification in a vineyard context (Vosne-Romanée, Burgundy, France) where medium-term soil budget and sustainability are controlled by complex interactions between natural processes (rill erosion) and anthropogenic processes (earth supply transferred back into the rills by the winegrowers). Concentrated overland flows during the rainfall event resulted in the incision of 13 major rills in the inter-rows, carrying a sediment volume of about 4.77 m3. Most of the rills were rectilinear and displayed a U shape with strong vertical walls. Rill incision began about 30 m from the upper plot boundary. In the buffer zone located at the lower border of the plot, seven fan systems developed from the material originating in one or two contributory rows. Accumulated volume is estimated at 1.6 m3. Data from grain-size distribution, and rill and fan volumes, show that erosion is dominated by rilling (70% of the sediment yield) over sheet process (30% of the sediment yield). The net exported soil loss, corresponding to the balance between natural soil loss and anthropogenic supply, ranges between 24±3 t ha−1 and 48 t ha−1, over the plot during one hydrologic event. Analyses of the grain-size distribution in the reference soil sample and in the fans reveal that size selectivity has occurred, with preferential export of the fine material (<63 μm) out of the plot, and preservation of the coarsest fractions (>2 mm) in the fans. To evaluate the relative importance in grain-size distribution of natural processes (material loss) over anthropogenic processes (rill-filling by winegrowers), we simulated the temporal evolution of grain-size distribution in surface soil during five successive rainfall events. Our results clearly show that more than 30% of fine material in surface soil was lost in these few events, despite anthropogenic rill filling. This fine-fraction removal may have considerable impact on vineyard sustainability.