Effects of fire on activity of some rangeland soil enzymes

Fire can severely affect vegetation and soil and prevent different cycles of ecosystems. Enzymes quantities are sensitive indices for soil quality, and the changes in their activity can affect the ability of ecosystem and alter nutrient uptake by plants. This investigation was carried out in Kordan rangeland in spring and autumn for two years. Soil was sampled from 0-20 cm depth. Three enzymes including acid phosphatase, alkaline phosphatase and dehydrogenase were assessed by reaction with substrate. Our results showed that the activities of all studied enzymes were significantly higher in soils in September at both areas. However, this difference was not high for alkaline phosphatase. Two years after fire, the activity of all studied enzymes was higher at control site. The reasons for this decrease may be due to the destruction of enzymatic system and increasing inorganic phosphate because of fire. Three years after fire, the activity of enzymes increased and for alkaline phosphatase and dehydrogenase was more than control site. These enzymes are considered as biological indices for soil microorganisms therefore, it can be expected that its increase indicates increasing microbial biomass in fire area.