Abstract: Based on field investigation and laboratory data,spatial distribution and temporal variations of biomass carbon density(BCD)in Pinus armandi forest ecosystem in Qinling Mountains were studied in this paper.The results showed:1) the organ distribution of BCD was 47.91％ for trunk,22.80％ for branch and 6.20％for bark,and BCD of different Pinus armandi organ ranged from 0.4916 to 0.5298,with the order as follows:barks>leaf>branch>trunk>root;2) the total BCD in Pinus armandi ecosystem was 183.26 t·hm^-2,about 2/3 of which was stored in the plant(including root) and 1/3 in the soil;3) the highest BCD values,70.48 t·hm^-2,occurred at the elevation ranging from 1?700 m to 1?800m;below the elevation of 1?500m or above the elevation of 1?900m the BCD values were 50.26 t·hm^-2　and 46.57 t·hm^-2 respectively;4) the highest and lowest BCD values were found in 50a and 20a respectively among the five age grades;and 5) comparing data of the two periods,biomass of forest Pinus armandi and BCD for 5 years increased by 3.12 t·hm^-2 and 1.61t·hm^-2 respectively.

Key words: Pinus armandi, biomass carbon density, Qinling Mountains