Combining 137Cs, 210Pb and dendrochronology for improved reconstruction of erosion–sedimentation events in a loess gully system (southern Poland)

Abstract

AbstractDetailed knowledge on the past events of erosion and redeposition is necessary to assess the frequency and magnitude of soil degradation and to provide more complete data, among all, to calculate rainfall thresholds and to develop strategies for controlling erosion. Therefore, in this study, we aimed to obtain a more comprehensive and accurate reconstruction of erosion–sedimentation events in a gully system by combining analyses of 137Cs and 210Pb with dendrochronological dating in the same sediment profiles. We aimed to precisely determine the number and the age of erosion–sedimentation events, which led to the development of study deposits and to determine the type of erosion providing material for deposition in particular events. To this purpose, 136 soil samples and 62 roots and tree stems samples were collected in eight research profiles at the gully bottom. We compared the results obtained with the two methods. Isotope analysis allowed us to estimate more general age of sediments and the type of erosion that provided material for individual layers. Dendrochronology provided a more precise reconstruction of the age of soil degradation events. By combining both techniques, we determined rainfall events responsible for erosion and sedimentation in the studied gully since 1980s and a rainfall threshold of 60 mm day−1 for soil erosion and redeposition in the study area.