Abstract: By using combustion method, this paper measured the carbon density in the tree, shrub, herb, and litter layers of six tree species plantations in a subtropical area of China. For the six plantations, the carbon density in different parts of trees varied, being the highest in leaf and trunk, followed by in branch, and the lowest in root and bark. Among the tree species, Pinus massoniana had the highest carbon density, while Mytilaria laosensis and Castanopsis hystrix had the lower one. The carbon density in different parts of understory shrubs had significant difference, with a similar pattern to that in different parts of trees, i.e., being the highest in leaf and branch, and the lowest in root. With the increasing density of the stands, the carbon density of understory shrubs presented a decreasing trend. In herb layer, the carbon density was higher in aboveground part than in belowground part, and had a similar distribution pattern to that in different parts of understory shrubs. In litter layer, the carbon density decreased rapidly from un-decomposed layer to semi-decomposed layer to humus layer. In the stand components, the carbon density was in the order of tree layer > shrub layer > herb layer > litter layer.

Key words: stock-scion, ¹⁵N, distribution, apple, nitrogen level, ¹³C, utilization.