Abstract: We explored the effects of different stand densities on calorific value in each component and the standing energy of community of Cunninghamia lanceolata under three stand densities (1800, 3000 and 4500 plants·hm^-2), in Xinkou Teaching Forest Farm of Fujian Agriculture and Forestry University, Sanming City, Fujian Province. The distribution of calorific value and energy in each component of ecosystem was quantified by measuring calorific value and biomass. The results showed that, on the vertical space, calorific value and the standing energy of each component of C. lanceolata changed with height, while the standing energy of the trunk and bark decreased with increasing height. The calorific value of the remaining dead branches and leaves increased with increasing height, while standing energy of the remaining dead leaves increased and then decreased with increasing height. The calorific value and standing energy of other components did not depend on height. As for the roots of different diameterclasses, the calorific value and standing energy of stump were the largest, while those of fine roots were the smallest. The distribution of calorific value in each component and the standing energy of ecosystem showed close correlation with stand densities. The calorific values of remaining dead branches, remaining dead leaves, litter and roots increased with increasing stand densities, while the opposite was true for understory vegetation, fresh branches and fresh leaves. The calorific value of trunk, bark, and remaining dead leaves first increased and then decreased with increasing stand densities. The standing energy of ecosystem exhibited an increasing tendency with increasing stand densities. As for the standing energy in different components of the ecosystem across different stand densities, trunk accounted for the largest proportion, followed by roots and barks, and the proportion of other components were all less than 10%. The calorific values of fresh leaves, branches, and understory were significantly negatively correlated with stand densities, while the calorific values of other components were not correlated with stand densities. The standing energy of understory vegetation was significantly negatively correlated with stand densities, the standing energy of remaining dead branches and litter was significantly positively correlated with stand densities, while the standing energy of other components was not correlated with stand densities. In conclusion, from the perspectives of ecology, economics and longterm development, a stand density of 3000 plants·hm^-2 is the most suitable for full use of biological resources and the growth of C. lanceolata.

Key words: stand density, Cunninghamia lanceolata plantation, standing energy stock, calorific value, component.