Variability of Soil Nutrients and Aggregate Stability in Different Times after Fire in Zagros Forests (Case Study: Paveh Forests)

The changes in soil nutrients and aggregate stability either in short-term or in long-term after fire is very important in forest ecosystems due to their key role in plants growth and preventing soil erosion. In the present investigation the short, medium, and long-term effect of fire was surveyed on these properties for the first time in Iran. For this purpose a plot of Zagros forests was selected where included three places with 1, 3, and 10 years after fire (treatments). Soil water repellency (WR), aggregate stability (AS), soil nutrients such as N, P, K, Na, Ca, and soil organic matter (SOM) content were measured. Results showed that water repellency and aggregate stability was significantly increased in one and three years treatments compared to control part. A significant decrease was in SOM, N, K and N in all fire treatments compared to their control. No changes were observed in soil texture while soil pH and EC significantly increased one year after fire. Soil P was significantly increased 1 year after fire, however, it was significantly decreased in 3 and 10 years after fire compared to their control. In contrast, no significant changes were observed 1, 3 and 10 years after fire compared to their control. It was concluded that depending on the time after fire, the significance increase in water repellency and consequently nutrient leaching can result in loss of soil fertility in long-term.