Evaluation of Plant Diversity Due to Natural Disturbance and SmallScale Harvesting in Sari Forests

Species composition and structure of forest stands change through time due to natural and artificial disturbances. Considering the importance of plant diversity, the present study intends to evaluate changes in species composition following disturbance in a natural ecosystem in the south of Sari city, Ojasarak. For this purpose, tree canopy in 58 sample plots with 400 m2 area were randomly measured in two regions. One 1 m2 plot at the center and Four 1 m2 plots at the corners of the sampling plot were marked to measure and collect the herbal plants. To evaluate biodiversity, Shannon-Wiener and Simpson diversity indices, species richness, curves of rank-abundance, K-dominance and rarefaction were used. The results showed that except Simpson index in biodiversity indices, there is not any significant difference between indices in two natural and artificial disturbances. Based on the results of rank-abundance curve, K-dominance and rarefaction, the diversity in natural disturbance is more than artificial disturbance, but richness in artificial disturbance is more than natural one.