Abstract: The transferring of heavy metals in poplar tree during its leaf fallen mainly occurs in the parts of leaf-branch, root and trunk. 8～48% of As and Zn in leaf is transferred to bark and timber, and the storage of Cu, Ph and Cd is increased. The internal cycling rate of As and Zn occupies 40%, and the external one of Cd, Ph and Cu occupies 17～27% of their storage. The purification efficiency of soil heavy metals by plants is also discussed in this paper.

Key words: Poplar tree, Heavy metals, Cycling, Purification efficiency, dissolved organic nitrogen, rhizosphere, dissolved organic carbon, nitrogen addition, elevated CO₂ concentration