Abstract: Despite of the significance in energy supply and society- and economy development,dam has been vehemently criticized because of its various ecological and environmental effects,especially the negative ones.The ecological effects of dam involve in wide range and long term,which cause certain influence on the ecology and environment through the changes in aquatic ecosystem and hydrological condition.Based on the characters of dam and watershed ecosystem,the latest researches were focused on the ecological effects of dam in regulating hydrological process and local ecological condition,barrier effects and insularity,intercepting effects,edge effects,and water thermal effects.Deriving from the concepts of food chain and web,this paper defined the ecological effect chain and web of dam,on the basis of analyzing the conception and connotation of ecological effect,and firstly,its history,and put forward the research directions on the ecological effects of dam,i.e.,1) what the ecological positive effects and the ecological effect chains and webs are,and how to explore,build and assess them,2) how to identify and underline the ecological effects on the ecosystem process and condition,3) how to address and distinguish the characteristics of each ecological effect at different temporal and spatial scale,make the relationships between them clear,and to scale down and up.These researches would avail our serious consideration to the planning,building,operating and managing of dams.

Key words: Oryza sativa, Heavy metal pollution, Genetic diversity, Corresponding analysis