Impact of Forest, Rangeland and Agriculture Land Uses and Climate on Soil Physical and Chemical Properties in Ilam Province

Climate and land use are two important factors which are greatly influence on soil physical and chemical properties. This research was conducted to study the effects of climate and land use on physical and chemical properties of soil in Ilam province in 2016. After initial studies, Ivan area with semi-humid climate and Ganjavan with semi-arid climate in Ilam province were selected. In each region, three land uses including forest, rangeland and agricultural were considered. After field studies in each land use, five soil samples were taken from 0-10cm and 10-30cm depths and collected randomly. The results showed that the highest amount of soil lime (47.85%) and soil silt (31.75%) were obtained in semi-arid climate of Ganjvan. The soils of Ayvan as a semi-humid climate had the highest amount of clay and K available. The highest bulk density (1.87 g.cm-3) was obtained in semi-arid climate of Ganjavan under the effect of agricultural use at lower soil depth. The lowest amount of bulk density (1.08 g.cm-3) was observed in semi-humid climate of Ayvan in the soil surface depth under forest land use. The highest amount of organic matter was obtained in forest land use in semi-humid climate in Ayvan, (42.85 %) which was more than semi-arid climate of Ganjvan. Agricultural land use had the lowest amount of organic matter (4.37%). The highest amount of N (0.514%) and P (35.04 mg kg-1) concentrations were obtained in forest land use in the semi-humid climate of Ayvan. The amount of Ca and Mg concentration in subsoil solution (10-30cm) layer was higher than topsoil solution (0-10cm) layer in Ayvan. In general, by changing land use from forest to farm, the percentage of clay, organic matter, nitrogen, phosphorus, and potassium available decreased in semi-arid climates of Ganjvan. Therefore, proper land use management in semiarid climates is essential for optimal preservation of soil properties.