Exploring the potential of using 7Be measurements to estimate soil redistribution rates in semi-arid areas: results from Western Iran and Southern Italy

Abstract

The need for further research to investigate the possibility of using 7Be as a soil erosion tracer under a range of climatic conditions, specifically in arid and semi-arid agro-environments, has been emphasised in the literature. In this context, this paper reports research conducted in two semi-arid areas located in Western Iran and Southern Italy in order to assess the potential of using 7Be measurements for estimating soil erosion over short timescales. The two study sites differ in terms of land use. More specifically, the area in Western Iran, under cultivation, is cropped mostly under wheat, barley and pea rotation. The area in Southern Italy has never been cultivated, has few eucalyptus trees, resulting from re-afforestation conducted in 1966 and retains a sparse grass cover. Soil sampling required two field campaigns undertaken in April 2011 and April 2016 in Western Iran and Southern Italy, respectively. In Western Iran, the 7Be reference inventory was estimated at 326 ± 40 Bq m−2 and the corresponding value of the shape factor was equal to 3.57 kg m−2. The soil loss was calculated to be 6.8 Mg ha−1, resulting in a Sediment Delivery Ratio (SDR) of ca. 80%. In Southern Italy, the 7Be reference inventory was equal to 180 ± 20 Bq m−2, emphasising a lower penetration of 7Be into the soil that is documented by a lower value of the shape factor (2.45 kg m−2). The overall results provided a net soil loss of ca. 20.7 Mg ha−1. In this case, no deposition was documented and a SDR value of ca. 100% was calculated. The magnitude of soil erosion reflects, for both sites, the steep topography, the different management system and the heavy rainfall occurring during a period that coincides with the absence of vegetative cover. The results obtained in this study are in line with similar studies carried out in other countries and suggest that, in cultivated areas, care must be taken when traditional cultivation systems are applied; in re-afforested areas, the presence of a uniform vegetative cover is crucial in protecting soil from erosion. However, there still is a need for further work to assess the feasibility of using 7Be in different areas and under different land uses or vegetation covers. Also, further refining of the conversion model, which is based here on the simple exponential function, are still possible.