The effects of habitat characteristics and human destructions on understory plant species biodiversity and soil in Zagros forest ecosystem

The stability and health of natural ecosystems can be dependent on plant species diversity. So determination the factors that control the diversity and have positive or negative effect on plant species diversity are very important in the ecology. With this aim four Oak (Quercous persica) sites in Ilam city were selected on the basis of history of management and disturbance: conservation management for 5 years, conservation management for 20 years, highly disturbed and undisturbed. The area of each site is approximately 100 hectare. Systematic-random sampling method (100×200 m) was used to gather data from 50 plots (400 m2) within each site. Three soil samples at the depths of 0–30 cm were randomly taken around the center of each sampling plot using soil auger, and then mixed to obtain 1 composite sample for laboratory analysis. Shannon index was used to determine the plant diversity. In this study the direct and indirect effects of each independent variable on the dependent variable evaluated using path analysis. Result showed that CEC, K, mg, NH4 and percent tree canopy had a positive direct effect on of Plant species diversity. Between these factors NH4 had the greatest influence. The most important factor in changing the Plant species diversity has been destruction, but it has a negative role by changing some soil properties and tree canopy.