Stable carbon isotopes as an indicator for soil degradation in an alpine environment (Urseren Valley, Switzerland)

Analyses of soil organic carbon (SOC) content and stable carbon isotope signatures (δ13C) of soils were assessed for their suitability to detect early stage soil erosion. We investigated the soils in the alpine Urseren Valley (southern central Switzerland) which are highly impacted by soil erosion. Hill slope transects from uplands (cambisols) to adjacent wetlands (histosols and histic to mollic gleysols) differing in their intensity of visible soil erosion, and reference wetlands without erosion influence were sampled. Carbon isotopic signature and SOC content of soil depth profiles were determined. A close correlation of δ13C and carbon content (r > 0.80) is found for upland soils not affected by soil erosion, indicating that depth profiles of δ13C of these upland soils mainly reflect decomposition of SOC. Long‐term disturbance of an upland soil is indicated by decreasing correlation of δ13C and SOC (r ≤ 0.80) which goes in parallel with increasing (visible) damage at the site. Early stage soil erosion in hill slope transects from uplands to adjacent wetlands is documented as an intermediate δ13C value (−27.5‰) for affected wetland soil horizons (0–12 cm) between upland (aerobic metabolism, relatively heavier δ13C of −26.6‰) and wetland isotopic signatures (anaerobic metabolism, relatively lighter δ13C of −28.6‰). Carbon isotopic signature and SOC content are found to be sensitive indicators of short‐ and long‐term soil erosion processes. Copyright © 2009 John Wiley & Sons, Ltd.