دور الطبوغرافيا واستخدام الأراضي في الانجراف المائي لترب المنحدرات الجنوبية للجبل الأخضر

Abstract

The role of topography and land use in water erosion of the southern slopes of Al-Jabal Al-Akhdar was studied. The experiment was carried out in agricultural and pastoral areas of Al-Jabal Al-Akhdar in eastern Libya, specifically in the regions of Marawa, Al-Masaylaba - Madur Al-Zaitoun, and Al-Qadida. Eight slopes were selected in each area, with a total of 24 different slopes in terms of slope intensity (moderate, gentle) and vegetation cover (natural, cultivated). Soil samples were taken from each slope with three replicates to estimate soil texture, soil structure, bulk density, moisture content, organic matter, calcium carbonate, pH, and electrical conductivity. Some field measurements were also taken for each slope, such as soil depth, infiltration rate, slope length, slope intensity, slope shape, slope direction, and vegetation cover ratio. The study aimed to compare the effect of topography and land use on soil erosion rates. The study did not find a significant difference between moderate and gentle slopes in terms of their physical and chemical properties, as only relative differences were recorded. Similarly, the study did not find a clear difference between natural vegetation and cultivated land in terms of their physical and chemical properties, as only relative differences were recorded, with a preference for agricultural land in terms of organic matter and infiltration rate. The annual soil loss rate was also calculated using the Universal Soil Loss Equation (USLE) for the study slopes, and the study found that annual soil loss rates were higher on moderate slopes than on gentle slopes. As for soil loss rates with different vegetation cover, the study found that annual soil loss rates were higher on agricultural land than on natural vegetation land. Geographic Information Systems (GIS) were also used to prepare soil erosion risk assessment maps for the study area.