Assessing the edge effect of forest road geometric plan in various forest types on plants biodiversity of adjacent stands (Case study: district No. 1 Dr. Bahram-nia forest- Gorgan)

The aim of this research was to assess the effect and range of each forest road geometric plans on biodiversity and composition of plants on its two sides. To this end, to study the biodiversity of species of lateral stands and the effects of environmental variables in the situation of establishment of plant species at different distances of the road, the comparison of Shannon biodiversity Index (H), Menhinick species richness and Smith-Wilson’s index of evenness, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used respectively, according to its geometric plans. Results of the comparison between biodiversity indexes showed that in both sides of the straight road to switch back, Shannon index and Menhinik richness increased, while Smith-Wilson evenness had an inverse trend. The results of DCA and CCA analysis showed that the distribution of demanding species was positively correlated with increasing light intensity and temperature on the road verge. The effect of the road on these species was up to a depth of 10 meters from its edge as well. Shade tolerant species were more in-depth of forest than the road.