Quantitative analysis of woody plants within the habitat of Caucasian black grouse (Lyrurus mlokosiewiczi Taczanowski) in the Arasbaran Forests, Iran

The Arasbaran Forests are the main habitat of Caucasian black grouse (Lyrurus mlokosiewiczi Taczanowski) as one of the most important endangered avian species in Iran. Quantitative analysis of the structure and composition of woodlands provides an appropriate basis for conservation programs in its habitat. This research was conducted to quantify the structural characteristics of woody communities in the Caucasian black grouse habitats in Iran. For this purpose, after determining the absence and presence regions, three one-hectare plots in each region were selected, in which all trees were inventoried. Results revealed that the greater amount of relatively large trees (DBH > 20 cm) and the vast range of tree diameter were observed in the presence area. The mean comparison showed that the mean of DBH (11.1±0.6 cm) in the bird's presence was significantly greater than that in the bird absences region (8.5±0.7 cm). The coefficient of variation of DBH, tree size diversity, tree species richness, tree height class richness, and tree heights in overstory were similar in both presence and absence areas. However, the tree and shrub heights in the understory were significantly greater in the presence area (1.5±0.06 m) compared with the absence area (1±0.02 m). Moreover, the abundance of dead trees was significantly different in those areas. In conclusion, the habitats with the relatively higher dominance of Quercus macranthera Fisch. & C.A.Mey. and the presence of dog rose (Rosa canina L.) and black currant (Ribes biebersteinii Berland.) are favorable for the black grouse. The relatively homogeneous structure with the presence of large diameter oak trees and the least amount of fallen dead trees provides suitable conditions for this species. This should be considered in the reconstruction of bird habitats and the restoration of previously manipulated habitats.