Abstract:Forests not only play an important role in hydrological processes but affect biochemical circles on the small watershed scale.Through canopy interception, litter and soil infiltration, as well as riparian vegetation strips, forest ecosystems have effective functions.These functions include sediment removal, soil erosion control, moderation of shade and temperature of stream, and improvement of water quality resulting from filtering, absorbing, and purifying sediments, organic matters, and pollutants from surface runoff.This paper reviews effects of forest vegetation change on small watershed hydrochemical circles, especially the impacts of forest harvesting on water temperature, sediments, and dissolved nutrients.Most of past studies in literature suggest that water temperature can be influenced by various forest harvesting patterns and that dissolved nutrients relate closely to harvesting patterns, sites, and catchment types.In forest watershed, riparian vegetation strips play a very important role in improving water quality.Riparian vegetation strips can maintain water temperature, prevent or reduce sediments, pollutants, and organic matters from entering stream channels.In order to provide better guidance for the national forest management, more researches on the effects of forest vegetation change（such as forest harvesting）on water quality are needed in China.