Relationship Between Plant Biodiversity and Topographical Factors in Forests of West Mazandaran (Case study: Research forest of Tarbiat Modares University)

Diversity is one of the most important issues in studies of vegetation ecology. This study was carried out in research forest of Tarbiat Modares University for surveying herbaceous and woody species diversity in relation to topographical factors (altitude، slope and aspect). For this purpose، 48 plots 400 m2 (20×20 m) were established in the region using selective sampling method. Then، the names and canopy cover of all herbaceous and woody species were recorded in the plots. In total، 137 herbaceous and 50 woody species were recognized which belonged to 167 genera and 72 families. In the case of herbaceous species، results showed that elevation factor had a significant effect on species richness، Margalef and Simpson indices. The species richness and Margalef’s index were highest in high altitudes (1450-1700 m a. s. l.)، and Simpson index was highest in high elevations (1200-1450 m a. s. l.). Slope had a significant effect on diversity and richness. Richness and Margalef index were higher in 60-90% slopes، and Simpson’s index was higher in low slopes (0-30%). In the case of woody species، results showed that elevation factor had a strong effect on all diversity indices. The results of correlations showed that indices of species richness، Margalef and Menhenick indices were reduced with an increase in altitude. Higher altitudes (1450-1700 m a. s. l.) showed higher amount of evenness. Also، the effects of slope and aspect were not significant on any woody species diversity indices.