Abstract: To transform large area pure conifer plantations by planting indigenous and valuable broad-leaved tree species has been advocated as an effective close-to-nature forest management in sub-tropical China. Taking the 10-, 20- and 27-year-old Castanopsis hystrix plantations in Guangxi of South China as test objects and by the methods of plot investigation and biomass measurement, this paper studied the carbon content in different plant organs, litter layers, and soil layers and the carbon storage and its allocation in tree layer, litter layer and soil layer. For the test plantations, the carbon content in different C. hystrix organs ranged from 49.7% to 57.9%, and that in litter layer was 40.8%-50.5%, being higher in fresh litter layer than in semi-decomposed litter layer. The carbon storage in the soil profiles (0-60 cm) increased with plantation age but decreased with soil depth. The total carbon storage in the 10-, 20- and 27-year-old plantations was 18242, 23475 and 26975 t·hm-2, respectively, among which, tree layer, litter layer and soil layer occupied 19.8%, 32.0% and 32.8%, 1.5%, 1.6% and 1.3%, and 78.7%, 664% and 659%, respectively. The annual net carbon sequestration of the 10-, 20- and 27-year-old plantations was 4.70, 5.64 and 5.18 t·hm-2, respectively. It was considered that C. hystrix had a high capability in carbon sequestration, being able to be an ideal tree species for multi-purpose forest management with large and valuable timber production.

Key words: Castanopsis hystrix plantation, carbon content, carbon storage, carbon allocation