Quantification of the Distribution and Changing Trend of the Ecological Niche of Brown Bear (Ursus arctos Linnaeus, 1758) in Ilam province

Ecological niche is an area of one or more of the environmental factors in which the growth, reproduction and survival of a living organism is possible. In this study, Maximum entropy method was used to model the distribution and quantification of bear ecological niche in Ilam province. To select the background points, the network bias was used using the kernel density method. 70 percent of the points were used for training and 30 percent were used for the test. The results showed that the model was successful in its running (AUC = 0.97) and had a significant difference with randomized design in all thresholds (P<0.05). In order to determine the variation of the ecological niche of the species in the distribution range, a 50% threshold (0.5) was applied to the habitat suitability map and the output of this map was used to determine the grid range. Grid selection was made according to the home range. For each network, the suitability map was cut and entered the ENMtools software to determine the ecological niches breadth. Non-parametric Mann-Kendall test was used to determine the process of ecological nest width changes. The results showed that altitude, NDVI and distance from semi-dense forests had the most effect on species distribution and bears in Manesht and Qalarang areas have the highest ecological niche breadth. The trend of ecological niche showed that the breadth of ecological niche of species from the northwest of the province to the south east has a significant decreasing trend.