Abstract: Cyclobalanopsis glauca is a constructive or dominant species of forest vegetation in karst region of south China, which has strong adaptability to rocky desertification mountain area. An experiment was conducted to explore the effects of three pioneer tree species, i.e.,Delavaya toxocarpa, Leucaena leucocephala, and Zenia insignis, on seedlinggrowth and twig and leaf traits of 1-3 years old C. glauca seedlings in rocky desertification area of southwest Guangxi, China. The results showed that the facilitative effect of three pioneer species on the survival and growth ofC. glauca seedlings were distinct, which was enhanced with the increases of seedling age. The facilitative effect on seedling height growth was greater than on basal diameter growth. The facilitation by D. toxocarpa was greater than by Z. insignis. Some parameters of C. glauca seedlings such as ratio of plant height to basal diameter, average internode length of stems, SPAD value of leaves, average area of single leaves and N content of leaves were larger under three pioneer tree species canopy than that outside canopy, whereas the C/N ratio of leaves was smaller. All these parameters of C. glauca seedlings were significantly different (P<0.05) between beneath D. toxocarpa or L. leucocephala and outside canopy. The specific leaf area of C. glauca seedlings was significantly greater beneathD. toxocarpa than outside canopy. According to the results of this study and previous studies, D. toxocarpa, L. leucocephala and Z. insignis can be chosen as the nurse plants to improve the establishment of C. glauca seedlings and thus the efficiency of vegetation restoration in rocky desertification region of southwest Guangxi, China.

Key words: stable isotope, bioaccumulation., food web, heavy metal