Effectiveness of carbon isotopic signature for estimating soil erosion and deposition rates in Sicilian vineyards

Abstract

Traditional methods for measurement of soil erosion provide information on erosion rates and mechanisms but fail to determine the spatial distribution of sediment redistribution. Recent studies have used carbon (C) stable isotopes to trace sediment and to monitor soil organic carbon (SOC) redistribution. The difference in δ13C values in a slope-transect or in a watershed provides information about the source of suspended organic matter and sediment removal and deposition, but miss enough information to quantify sediment loss. The objective of this research was to develop a method to estimate soil erosion using the natural discrimination of δ13C-SOC with soil depth, comparing δ13C variation in different profiles sampled along a slope. The method was developed in a Sicilian vineyard, where soil losses were previously measured by means of Gerlach collectors and by pole methods. δ13C was measured in different soil profiles in the top, middle and bottom of the slope. The variation of δ13C with soil depth in the profiles along the slope was compared to the δ13C values of the near flat area, in order to reconstruct the original topography of slope transect. δ13C increased with depth and decreased from the top to the bottom of the slope in all pedons. The soil δ13C signature ranged from -26.7‰ to -25.7‰, from -26.2‰ to -25.3‰, and from -27.0‰ to -24.8‰ in the profiles at the top, middle, and bottom of the slope, respectively. The rates of δ13C enrichment along the slope could be explained as different rates of detachment and deposition. The erosion value estimated with δ13C method was 77Mgha-1y-1. The comparison of different methods (102Mgha-1y-1 with the pole method and 89.6Mgha-1y-1 with the Gerlach method) indicate that carbon isotopic signature is a reliable indicator of short- and long-term soil erosion processes.