Detecting Anthropogenic Disturbance on Weathering and Erosion Processes

Abstract:

Anthropogenic disturbance of natural vegetation can profoundly alter the physical, chemical and biological processes within soils. Rapid removal of topsoil during intense farming can result in an imbalance between soil production through chemical weathering and physical erosion, with direct implications on local biogeochemical cycling. However, the feedback mechanisms between soil erosion, chemical weathering and biogeochemical cycling in response to anthropogenic forcing are not yet fully understood.

In this paper, we analyze dynamic soil properties for a rapidly changing anthropogenic landscape in the Spanish Betic Cordillera; and focus on the coupling between physical erosion, soil production and soil chemical weathering. Modern erosion rates were quantified through analysis of sediment deposition volumes behind check dams, and represent catchment-average erosion rates over the last 10 to 50 years. Soil production rates are derived from in-situ produced ¹⁰Be nuclide concentrations, and represent long-term flux rates. In each catchment, soil chemical weathering intensities were calculated for two soil-regolith profiles.

Although Southeast Spain is commonly reported as the European region that is most affected by land degradation, modern erosion rates are low (140 t ha⁻¹ yr⁻¹). About 50 % of the catchments are losing soils at a rate of less than 60 t km⁻² yr⁻¹. Our data show that modern erosion rates are roughly of the same magnitude as the long-term or cosmogenically-derived erosion rates in the Betic Cordillera. Soils developed on weathered metamorphic rocks have no well-developed profile characteristics, and are generally thin and stony. Nevertheless, soil chemical weathering intensities are high; and question the occurrence of past soil truncation.