Research Info

This study investigated the impacts of two land uses, namely natural oak forests and abandoned rainfed farming, on the long-term redistribution of soil properties in the hilly regions of the semi-arid western part of Iran. We assessed cesium-137 (137Cs) levels in the soil to determine soil erosion and sedimentation rates. We explored the consequences of deforestation and the conversion of an oak forest to rainfed farmland abandoned for over a decade. We measured various soil properties, including magnetic susceptibility, aggregate stability, and soil organic carbon (SOC) levels in different soil fractions. For both forest and abandoned rainfed farming land uses, three slope positions (upper, mid, and lower) were selected. Two soil samples were collected from a depth of 0–20 cm from each slope position. 137Cs analysis revealed that the greatest 137Cs loss occurred at the upper-slope position in both the natural forest (14.5 %) and abandoned rainfed farming (74.1 %) land use. A simplified mass balance model demonstrated average erosion rates of 109 and 706.2 t ha􀀀 1 yr􀀀 1 in the natural forest and abandoned rainfed farming areas, respectively. The highest erosion rates were recorded at the upper-slope positions of both land-use areas, which was primarily attributed to lower soil organic matter (SOM) and vegetation. Furthermore, we observed lower magnetic susceptibilities in the upper-slope position of both land uses, coinciding with the areas experiencing the highest levels of soil loss. Particulate organic carbon and total nitrogen contents in the sand-sized and larger aggregates in the natural forest land use were significantly higher compared to those in the abandoned rainfed farming land use (p < 0.05). A similar trend was observed for the SOC content associated with various aggregate sizes. In conclusion, the conversion of forest land use to abandoned rainfed farming land use on slopes can lead to soil degradation and redistribution due to accelerated soil erosion and deposition.