HEDGES, COLLUVIUM AND LYNCHETS ALONG A REFERENCE TOPOSEQUENCE (HABSHEIM, ALSACE, FRANCE): HISTORY OF EROSION IN A LOESS AREA

Lynchets are topographic ledges that are formed by the accumulation of colluvium behind a hedge grown perpendicular to the slope of a hillside. This colluvium constitutes a natural archive for the analysis of agricultural erosion over time, as we demonstrate in this study of a toposequence characterized by two lynchets along a loess slope. The detailed description of the soil catena coupled with OSL dating records the major erosional phases. The earliest phase begins during the late Neolithic at ca. 5,760 +/- 500 yr. The upslope hedge is installed at ca. 2,710 +/- 200 yr, at the very end of the Bronze Age or the beginning of the Early Iron Age and the downslope hedge is planted during the Early Middle Ages. Therefore, onwards from 2,710 +/- 200 yr, erosion only affects individual plots or sections rather than the entire slope. Our dates also show that the soils on the uppermost portion of the slope had undergone a complete ablation prior to 2,710 perpendicular to 200 yr. This early erosional phase, likely Neolithic in age, is consistent with other dates obtained in the northern Alsace region.