Selective cutting (single and group selection method) is most usual forest harvesting method in the Hyrcanian forests. In order to investigate impact of single selection method on the Hyrcanian forest two logged and unlogged sites in the Kheyrud forest research station of Tehran University, Mazandaran province, were selected. In each site 30 circle sample plots (1000 m2) by randomized-systematic method in a net of 100 m × 100 m were collected. In every sample plot the data including the species, number of trees, diameter at breast height (cm) and height (m) were recorded. Afterward, in each sample plots the micro plots of 10 m × 10 m (100 m2) were designed to record of shrub information. Species diversity index including Shannon Wiener (H ׳), Simpson (1-D) and Margaleff (R1) was used to diversity analysis. To data analyzing, used was made of the Ecological Methodology software (V.7) and SPSS18 software. The results showed the numbers of 9 and 11 in the logged forest and 5 and 7 in the unlogged forest for the species richness of trees and shrubs, respectively. Fagus orientalis Lipsky and Carpinus betulus L were the most dominant tree plants and Ilex spinigera (Loes). Loes. and Rubus persicus Boiss has dominant shrub plants in this area. Tree and shrub diversity in the unlogged area has higher means diversity index and differences between tree and shrub diversity indexes in the two areas were statistically significant. Results showed that shrub layer had the higher diversity indices (richness, diversity and evenness). In total Single selection method Logging has negative effect in the tree and shrub diversity.
