In order to investigate structural diversity of oak forest, Blake forest in the Baneh region, Kurdistan Province was selected. Inventory sampling by random method and three sample plots (100 m by100 m) were sampled. In every sample plot the number of tree and shrub species, diameter at breast height (DBH) and height (m) was recorded. Analyses of biodiversity were done using heterogeneity indicators of Shannon Wiener (H‫)׳‬ and Simpson (1-D) as well as evenness using Margalef (R 1 ) indices. The

more »

... diameter divided in 10 cm classes and the height divided in 4 m height classes and dominant height. Anova was used to analysis all indices means differences in the DBH classes and high classes. To analysis data use the Pest software. Results indicated that Rosacae families have the highest number of species. Quercus libani Oliv and Quercus infectoria Oliv were the most dominant woody plants. The results showed with increase of diameter and height classes species diversity decreased. A significant different was observed between tree diversity of the diameter and height classes (level of 1%). Thus, the study of biodiversity changes in different diameter and height category cause ecologically precise perspective in management of forest stands.