Abstract: Forest road has far-reaching effects on plant species diversity across varying scales, and the estimation of its effect distance and effect zone is a key issue to integrate the road effect and ecological processes in forest area. In this paper, ten transects，2 m wide and extending 50 m from varying grade roads including main road, main line for wood transportation, and secondary line for wood transportation in Huzhong forest area of Great Hing’an Mountains were set. The plant composition was investigated in twentyfive 2 m×2 m plots of each transect. The road-effect distance on plant species diversity identified by moving window analysis in terms of the important value of each plot. The results showed that in study area, the effect distance reached up to 20-34 m, regardeless of  the roads grade. The plant species diversity of shrub stratum and herb stratum within the effect zone was greater than that in adjacent habitat, with the Shannon-Weiner index increased by 21% and 60%, respectively. The response of shrub stratum to the road effect was more stable than herb stratum, but no significant change was observed in tree stratum. Chamaenerion angustifolium was the indicative species of road-effect zone communities. Based on the estimation of road-effect distance, the road area in Huzhong Forestry Bureau and Great Hing’an Mountains occupied about 0.10%, and its effect zone on vegetation occupied 1.79% and 1.53%, respectively.

Key words: Great Hing’an Mountains, forest landscape, road, plant , diversity, effect distance, effect zone, water potential, gas exchange, chlorophyll fluorescence, stomatal limitation, non-stomatal limitation.