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چکیده
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Forest roads are among the most important preconditions for management of forest ecosystems. The Kheiroud investigation forest, Northern, Iran has about 50 kilometers of road network since 1960. In order to evaluate the ecological effect of forest roads on adjacent vegetation, we selected a part of the main branch of this road network (22 km). Vegetation sampling was carried out using 22 transects, placed at two kilometer distances, perpendicular to the road axis. In each transect, six sample plots (2×10 m) were placed at 0, 5, 10, 25, 50 and 100 meters form road edge (132 plots in total). In each sample plot, environmental variables and vegetation data were collected in April-May 2013. TWINSPAN, indicator species analysis and direct ordination (CCA) were used to analyze the effect of road and environmental variables on vegetation composition. Among 100 plant taxa recorded, 20 species have been found only in roadside sites. The TWINSPAN run resulted in seven distinct groups. The first group consists of 19 plots, with Mentha aquatica as the main indicator species, merely belonging to adjacent and wet roadsides (zero distance to the road). Indicator species analysis also resulted in 26 species, among them 23 species represented zero distance from the road side, one species (Ulmus glabra seedlings) represented 10 meters and two species (Epimedium pinnatum and Euphorbia amygdaloide) represented 100 meters distance from the road edge. Forward selection in CCA analysis resulted in 10 significant variables out of the initial set of 38 variables. Among them; zero distance from the road, litter depth, relative light intensity, inclination, elevation and forest type had the most influence on plant composition (22.44 % of total variation). Our result show that roads can change vegetation composition up to 10 meters distance from the road edge, promoting light demanding, ruderal and exotic plants like Mentha aquatica, Equisetum telmateia, Rumex sanguineus, Prunella vulgaris, Sa
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