Assessment of forest cover change trends and determination of the main physiographic factors on forest degradation in Ilam province (case study: Sirvan county)

Monitoring of the changes in land uses and forest degradation is an important issue in evaluation and management of the natural resources. In order to investigate the forest cover degradation trends and determination of the main environmental factors on forest degradation in Sirvan county of Ilam province, satellite images for the years 1987 and 2014 of MMS (80 m spatial resolution) and OLI (30 m spatial resolution) were used. To survey the spatial relationship of forest cover reduction with the main environmental factors, regression logistic statistics method was used. The results revealed that about 5910.15 ha of the forest cover has been reduced Sirvan county during 27 years. In addition, the results of modelling demonstrated that altitude, slope and aspect variables (α≤0.01) were the most affecting factors on forest degradation in the studied area, respectively. While distance to road and distance to villages had no significant effects (α>0.01) on forest degradation in this area. Assessment of regression model fitted with ROC (0.9045) and Pseudo-R2 (0.3275) indices indicated the ability of the model to describe the changes and to identify the areas prone to change.