تغییرپذیری برخی از خصوصیات کیفی خاک سطحی در مقیاس زمین‌نما در اراضی مرتعی اطراف شهرستان سمیرم

Understanding the variability of pedological properties as well as the soil quality attributes on different landscape positions in hummocky terrains would result in a better land management in such areas. Despite the importance of such studies, no research has been couducted on the landscape-scale variability of soil quality indices in Iran and most researchers have so far focussed on pedological aspects of soil variability. The objective of this study was to understand the variability of selected soil quality indices at different landscape positions. A systematic grid including 120 points (12x10) with a distance of 30m was laid out in a hummocky rangeland around the city of Semirom. Surface soil samples were taken from 120 points on grid nodes and their organic carbon, microbial respiration rate, phosphatase activity, pH and EC were measured. Also, the thickness of A horizon and the soil moisture content were measured on grid nodes in the field. The results indicated that the lower slope positions including footslope and toeslope had the highest amount of phosphatase activity, microbial respiration, A horizon thickness, organic carbon, and EC. In contrast, soils occuring on shoulder had the least amount of the above-mentioned properties. Soils on summit and backslope seem to have been moderately degraded. Soil pH showed the opposite trend, as compared to other properties studied. The presence of a great variability in soil quality attributes at the landscape scale can be attributed to differenes in effective moisture that various landscape positions receive, as well as the differenes in soil erosion and deposition rates. This can also be an indication of a severe land degradion due to poor management practices. Since applying different management practices on different landscape positions are practically impossible, to be on the safe side, it is highly recommended to plan conservation practices based on soil quality of the most degraded landscape positions.