Abstract: Employing standard tree regression analysis (for trees) and harvest method,the biomass of tropical secondary forest dominated byMallotus paniculatus in Xishuangbanna was studied. Total biomass of a 10-year-old community was 57.819 t穐m^-2,with the biomass of tree,shrub,inter-layer and herb layers 51.019 t穐m^-2 (88.24% of community biomass),5.644 t穐 m^-2 (9.76%),1.013 t穐m^-2 (1.75%) and 0.143 t穐m^-2 (0 25%),respectively. From the 5-year-old to 10-year-old plant community,biomass of tree,shrub and inter-layer layers increased by 105.04%,122.73% and 93.32%,respectively,while that of the herb layer decreased by 83.53%. The biomass was mainly concentrated in a few dominant species in the tree layer. Biomass of Mallotus paniculatus,Litsea sp. and Ficus sp. reached 26.170 t穐m^-2,accounting for 51.29% of tree layer biomass. The smaller DBH classes mainly contributed to the biomass of tree layer,and organs in the tree layer ranked in order of stem>branch>root>leaf.

Key words: Bird island, Qinghai Lake, Species diversity, Soil environmental factors