Frequencies evaluation in estimation of tree species diversity in degraded forests Case study: Kouhmian forests, Azadshahr, Golestan province

Aim of this research was evaluated and compared of density (number tree per hectare), basal area and volume characteristics for estimation of tree species diversity in degraded forests. In order to, 73 hectares of Kouhmian forests was inventory based on random systematic pattern with circular plots (10R and 26 plots). In each plot species, DBH and number of tree were measured and recorded. To estimate of tree species diversity was used from Simpson, Hill’s N2, Shannon-Wiener and Mc Arthur’s N1 indices and for calculation of evenness and species richness were used from Wilson- Smith’s and Margalef indices respectively. Also species importance value (SIV) was calculated. The results showed that forest structure is irregular and uneven structure. Also the results showed that in calculation of diversity and evenness indices, if density is selected as calculation criteria, amount of these indices is more than to volume and basal area that are selected as calculation criteria. The results of SIV showed that the highest value of SIV belonged to Carpinus betulus (212.52%) and the lowest value belonged to Zelkova carpinifolia (6.82%). Also Margalef index showed that amount of richness is equal to 1.13.