Abstract: To reveal the effects of different restoration modes after returning farmland to lake on the soil biological characteristics in Dongting Lake area, the activities of soil saccharase, urease, phosphatase, and catalase at three typical sites (Xiaojicheng, Guanyuan, and Qingshanyuan) were studied. At the Xiaojicheng site where poplar was planted, soil catalase activity increased significantly, but the activities of other three test enzymes had no significant change. At the Guanyuan site where reed was planted, the activities of soil saccharase and phosphatase had somewhat decrease, and those of urease and catalase had less change. At the Qingshanyuan site where natural water area was restored, the test enzyme activities had less changes except that the phosphatase activity decreased. Correlation analysis showed that the test enzyme activities had significant positive correlations with soil organic matter content (P<001), illustrating that the changes in the soil organic matter content under different restoration modes could be the main cause inducing the changes in soil enzyme activity.

Key words: returning farmland to lake, enzyme activity, restoration, soil organic matter, non-structural carbohydrates, xylem, radial and axial variation,  Betula platyphylla, Tilia amurensis, shade tolerance.