Impact of forest roads on flora, life forms, and chorology of plants in Hornbeam-beech Kheyrud forest

Constructing forest roads network is a kind of human intervention that causes disturbances in the forest. The aim of this study was to determine the effective distance of secondary forest roads on flora, life forms and chorology of plants in Hornbeam-beech Kheyrud forest in Nowshahr. For this purpose, 36 transects with a length of 100 m (eighteen transects at each fill slope and cut slope) were selected from the road edge into forest interior. Along each transect, 8 plots of 2 × 1 m were collected by intervals of zero (road edge), 5, 10, 15, 20, 30, 45 and 100 meters. The results showed that the maximum effective distance of road on the flora was 15 meters, because in other distances, the frequency of Fagaceae and Betulaceae plants became dominant, and moreover, presence of Rosaceae, Cyperaceae and Poaceae plants decreased. Furthermore, the maximum effective distance on life form was 20 meters, as a result, after this interval percentage of geophytes and hemicryptophytes decreased, however, there was an increase in percentage of phanerophytes. Also, the forest roads effect on chorology were up to a maximum distance of 15 m. Cosmopolitan and sub-cosmopolitan chorotypes were not exist in higher distances and the presence of multiregional species was declined. Dominant form of distribution altered in the form of Europe-Siberia or Europe-Siberia and Mediterranean. Using the excavator instead of bulldozer for the road constructing that provide less environment disturbance and strict compliance with longitudinal and transverse profiles of forest roads can reduce the negative effects of roads on ecosystem.