Abstract:

Carbon accumulation and distribution were studied in three plots of a 13 years old Chinese fir (Cunninghamia lanceolata) forest in Daqingshan, Guangxi. The results showed that the average carbon concentration in all organs was in the following order: leaf (510.5)>bark (501.8)>wood (485.1)>root (476.5)>branch(462.1) (g·kg^-1). The carbon concentration of soil (to 60 cm depth) ranged from 11.4 to 21.1 (g·kg^-1), with an average of 16.6 (g·kg^-1). Carbon concentration of surface soil (to 20 cm) was higher than the other layer. The average carbon concentrations (g·kg^-1) in different layers were in the order as: trees (497)> shrub (437.5) >standing litters (437.5)>herb (407.8). The carbon storage of the forest ecosystem was in order of soil layer>vegetation >standing litter. Of total average carbon, 23.87% was in vegetation component, 74.27% in soil (60 cm depth), and only 1.86% in standing ground litter layer. The tree layer occupied 22.93% of total carbon storage in the ecosystem and 96.07% of carbon storage in the vegetation layer. The carbon storage in different organs was positively related to the biomass of corresponding organs. Trunk accumulated the highest carbon storage, comprising 58.40% of carbon storage in tree layer. Secondly, root made up 20.09% of total tree carbon. The annual net productivity of Chinese fir plantation was 10.10 t·hm^-2a^-1, stored carbon up to 4.67 t·hm^-2a^-1, equal to 17.13 t·hm^-2a^-1 of CO₂. Chinese fir plantation was an important sink of atmospheric CO₂. But its capacity of C sequestration decreased gradually in this region.

Key words: biomass, carbon storage, spacial distribution, Cunninghamia lanceolata plantation, extreme zone, lower subtropical area