Vegetation and Forest Complexity Analysis of the Caucasian Grouse (Lyrurus mlokosiewiczi) Habitats in the Lesser Caucasus Mountain

Species composition can vary among different types of habitat and is defined by the dependency of species on resources. The positive relationship between species composition and forest functions is of increasing interest to researchers. In this study, we focused on the species composition and structural complexity index (SCI) of the Caucasian grouse (Lyrurus mlokosiewiczi) habitat, which is an indicator species in mountain forest habitats in the Arasbaran biosphere reserve, Iran. Data were collected from the previously identified presence and pseudo-absence locations of this species. A total of 18 sample plots were surveyed systematically randomly in each area with 800 m distance from each other (36 sample plots in total). The main parameters were type of species, diameter and height of trees, shrubs and regeneration, and number and diameter of coarse woody debris. Overstorey tree species richness per ha differed in the pseudo-absence and presence locations, with 16 and 20 species, respectively. The Caucasian grouse was observed in the site with trees smaller than 10 cm DBH and a balanced density of trees smaller than 5 cm DBH. Overall, the SCI was higher in the presence location than in the pseudo-absence location with no significant difference (t = 1.491, p-value= 0.154). The heterogeneity of the stand structure in grouse habitats was high. The area where the Caucasian grouse was present was characterized by high numbers of dead trees and also high log volume. Maintaining a heterogenous forest structure is important for protecting this species. Conservation of fruit trees that are fed on by the grouse is also recommended.