Abstract: From July 2007 to May 2008, an investigation was made on the hydrology, physical form, streamside zone, water quality, and benthic organisms in several streams that flow to the Danjiangkou Reservoir. By using a river health comprehensive assessment index, the river ecosystem health of the streams was assessed. In upstream reaches, the river ecosystem health was good; while in downstream reaches, the river ecosystem health was bad, because of the physical form change, increased autotrophic index, and decreased macro-benthic invertebrate diversity. It was suggested that to maintain the river ecosystem health of the streams flowing to the Danjiangkou Reservoir, the eco-environment in upstream reaches should be protected, and the destroyed physical form in middle reaches should be restored.

Key words: Gap, Regeneration, Tree seedling, Evergreen broad-leaved forest, Ailao Mountains