Abstract:

The forest biomass provides an important information for forest carbon storage estimation and carbon source sink assessment. Based on the consecutive forest resource inventory data，the biomass carbon density (BCD) of dark coniferous forests（DCF） in the upper reaches of Minjiang River was calculated by using biomass expansion factors (BEF) method and its variation with age class，elevation and aspects were also examined. The results showed: The higher BCD was found in mature and overmature DCF and the lower BCD in young and middle aged DCF; For the same age class，the BCD values of the mature and overmature DCF were higher than those of the national average，while the BCD values of the middle age and premature DCF were lower than those of the national average，the BCD value of the young forest was similar to the national average; The annual increment rates of BCD in middleage，young and overmature DCF were 1.3%，0.8% and 0.7%，respectively; The higher BCD values occurred at the site with the elevation ranging from 3 600 to 3 800 m; The annual increment rate of BCD was found to be highest (1.03%) at the site with the elevation between 3 200 and 3 600 m; The higher BCD and its annual increment rate of BCD occurred on both north facing aspects and southwest and southeast aspects，while the lower values occurred on south facing aspects; The BCD of DCF in the upper reaches of the Minjiang River have been increasing over the past 20 years，the annual increment rate of BCD was 1.15% from 1997 to 2002, which was the highest among the five inventory periods.

Key words: dark coniferous forest, biomass carbon density, biomass expansion factors, Minjiang River