Results/Conclusions  Our results showed that wide and narrow roads had different edge effects.  For the wide roads, plant diversity and soil moisture tended to increase, whereas herbaceous biomass tended to decrease, from the road edge to the forest interior.   Tree biomass and soil pH at the road edges were significantly higher than those in the forest interior.  No significant difference between the edge and the interior was found, however, in terms of soil microbial biomass carbon, available phosphorus, organic matter content, and total soil nitrogen.  For the narrow roads, none of the measured variables showed a statistically significant difference between the edge and the interior.  Our study suggests that forest roads tend to increase plant biomass mainly because of increased light availability, but reduce plant diversity probably due to increased competition, in the edge zone of a forest.  It also suggests a threshold width of roads for edge effects to take place, which is between 2 and 8 m for the study forests.  These findings have important implications for forest conservation and landscape planning in this region so as to maximize biodiversity and minimize habitat fragmentation and edge effects.