Abstract: Mixedspecies forest plantations have been established in a large area in the tropics of China, playing an important role in carbon sequestration. To understand the changes in annual growth and biomass allocation, we investigated height (H), diameter at breast height (D) and basal diameter (BD) from different aged rubber plantations (8-, 11- and 20-year-old) mixed with Rauvolfia vomitoria and Flemingia macrophylla (RM) and adjacent pure rubber plantations (CK) in Xishuangbanna, in December 2013 and 2014. Also, the biomass regression models were established. The annual growth in D or BD and biomass increment of different trees in RM decreased with increasing stand age. The D’s annual growth of rubber trees in 8-, 11- and 20-year-old RM was 1.16, 1.01 and 1.17 times of that in CK, with annual biomass increment being 1.13, 1.08 and 1.49 times, respectively. The total biomass was 111.16, 112.53 and 119.53 t·hm^-2 in the 8-, 11- and 20-year-old RM, respectively, being 1.35, 0.60 and 0.17 times higher than that in CK. However, the total biomass increment decreased with stand age, ranging from 53.20 t·hm^-2 in 8-year-old RM, 33.64 t·hm^-2 in 11yearold RM to 11.18 t·hm^-2 in 20-year-old RM, which were 5.13, 4.48 and 2.63 times of that in CK respectively. The relative contributions of stems and branches to total biomass increased with stand age in both RM and CK, while the contributions of leaves and roots decreased. The results suggest that biomass accumulation will be greatly enhanced by constructing mixed-species rubber plantation.

Key words: oriented object, multi-resolution segmentation, vegetation classification, vegetation index.