Abstract:

Carbon content values of eight tree species in the region,i.e.,Pinus massoniana,fast growing acacia,chinese fir,eucalyptus,slashpine,hardwood,softwood,and Castanopsis fissa,were measured based on the wet burning approach.In addition,carbon content of these trees with respect to several potential influencing factors,i.e.,tree species,tree organs,diameter grades,and vertical trunk positions,were analyzed.Experimental results showed that:1)with respect to tree species,the carbon contents in descending order are:slash pine > chinese fir > Pinus massoniana > fast growing acacia > hardwood > eucalyptus > softwood > Castanopsis fissa .2)With respect to tree organs,the descending carbon contents are:leaves>branches>bark>trunks>roots,and the carbon content decreased when the positions of these organs located from top to bottom or from outside to inside.3)With respect to vertical trunk positions,the carbon contents of all eight species are very close,and coefficients of variation for those species are all less than 3.64%. 4)With respect to diameter grades,variation amplitudes of carbon contents of sampled trees in Guangdong are relatively small.However,for the same tree species,the carbon contents of different organs from the same tree species varied with their diameter grades,and the carbon content increased firstly and then decreased along with the increasing of diameter grades or vertical trunk positions.No correlations were observed between the rates of diameter grades and that of vertical trunk positions.For samples under the same vertical trunk positions,the carbon content rised in the beginning and then descended with the rises of diameter grades.In general,significant differences in carbon content were perceived among different tree species,or different tree organs of the same species,or distinct influencing factors of the same species.The accurate determination of carbon contents in various areas,tree species and forest ecosystems can provide a scientific basis for improving the accuracy of estimating their carbon reserves.

Key words: trees, carbon content, tree organs, vertical positions, diameter grades