Identifying the most important factors affecting the distribution of Ash (Fraxinus excelsior L.) and detect potential habitats areas in Kherudkanar Nowshahr forest

The aim of this research was to identify the optimal habitat areas of ash species (Fraxinus excelsior L.) in Kheyrud Nowshahr forest, which covers an area of approximately 8,224 hectares. We recorded the geographical coordinates of 1004 ash individuals using a GPS device, along with environmental variables such as climate variables and primary and secondary topographic predictors extracted from DEM. We used the predictors with the least degree of correlation as input in the Generalized Linear Model, Generalized Additive Model, Random Forest, and maxent models. We prepared and analyzed the variables in ArcGIS, SAGA, and R software. To compare the performance of the four models, we considered the input variables in all models to be the same. We evaluated the models using kappa coefficient (K), Area Under Curve (AUC), and True Skill Statistic (TSS) measures. The RF model had the highest K (0.973), AUC (0.997), and TSS (0.973), indicating the best performance among the models. According to the RF model, the most important variables were valley depth, profile curvature, slope, and topographic position index. These variables indicate the areas with rich soil, sufficient moisture, proper drainage (non-stagnant water), slope less than 45%, and sufficient light (suitable for the vegetative stage). We identified the most suitable areas in the Baharbon, Chelir, and Menia-Sang districts due to optimal conditions for these effective variables.