Abstract: In order to quantify the potential carbon (C) sink of the rubber plantations in Xishuangbanna and to understand the implication of the C sink to the regional C budget and future forest management, six age classes (5, 9, 14, 19, 23, and 26 years old) rubber plantations in suitable (low elevation, 550-600 m) and less suitable (high elevation, 950-1050 m) planting regions of Xishuangbanna were selected to estimate their biomass C stocks. In suitable planting region, 19-year-old plantation had the highest aboveground net primary productivity (16.22±3.47 t·hm^-2·a^-1), while in less suitable planting region, 23-year-old plantation had the highest one (8.65±3.46 t·hm^-2·a^-1). The maximum total aboveground biomass of the plantations in suitable and less suitable planting regions was 205.82 and 139.76 t·hm^-2, and the corresponding intrinsic rate of natural increase of biomass was 21% and 14%, respectively. The maximum total biomass carbon stock of the plantations in suitable and less suitable planting regions was 123.49 and 83.86 t C·hm^-2, respectively, being obviously lower than that (311.41±66.46 t C·hm^-2) of the local tropical seasonal rain forests. The total biomass carbon stock of the plantations in suitable planting region was slightly higher than the average value (121 t C·hm^-2) of the tropical forests in the world. By 2008, the total biomass carbon stock of the rubber plantations in Xishuangbanna was 16.54×10⁶ t C.

Key words: Macrophytes, Community pattern, Semivariogram, Fractal theory