ASSESSING SOIL QUALITY THROUGH SOIL CHEMICAL PROPERTIES AND ENZYME ACTIVITIES IN SEMIARID AREA, IRAN

Semiarid ecosystems are more sensitive to environmental changes than other terrestrial ecosystems, which makes their monitoring very important. Determining soil quality is critical to precise monitoring of semiarid area, and its evaluation involves the assessment of soil properties. In this study, the soil chemical properties and enzyme activities were measured and compared in order to determine soil quality. Four plots were chosen in the cold and warm sites in the Khabr national park and Ruchun wildlife refuge with grazed and not grazed areas. Samples of surface soil (0-10 cm) were collected in spring and autumn. The results showed that chemical properties of the soils were significantly affected by site (soil organic carbon, total nitrogen, available phosphorus and soil moisture) and season (pH, total nitrogen, available phosphorus and soil moisture) but not by grazing. All assayed enzyme activities were significantly influenced by site and season. Alkaline phosphatase activity was affected by grazing, too. Soil chemical properties (soil organic carbon, total nitrogen, and available phosphorus content and soil moisture) and enzyme activities (acid phosphatase, alkaline phosphatase, invertase, beta-glucosidase, urease and arylsulfatase) showed higher value at cold sites. The positive correlation between all assayed enzymes and soil organic carbon (r= 0.189-0.639) indicated the important role of soil organic carbon availability in soil enzyme activities. Seasonal variation was observed in soil chemical properties except for electrical conductivity. In addition, temporal variation was observed in enzyme activities with more activity in spring samples except for arylsulfatase activity. According to more value in nutrient content and enzyme activities, it can be concluded that soil at cold sites have higher quality than warm sites. In conclusion, the warm sites with poor soil quality need more concern to be protected.