Biomass expansion factor of aged sugi (Cryptomeria japonica) stands in the University of Tokyo Chiba Forest

Abstract

Change of biomass expansion factor (BEF) by stand age was analyzed using the published data of aboveground biomass of Cryptomeria japonica stands. The BEF tended to become small according to stand age and mean height. The relationships between BEF and stand age or mean height of the University of Tokyo Chiba Forest weren't different from those of other prefectures. The mean BEF of the stands older than 80 years old was 1.14 ± 0.05 (mean ± sd), which was smaller than 1.23 of the BEF used in the IPCC report for the stands older than 21 years old. Leaf biomass of the old stand tended to be same or less than that of young stand. Branch biomass of the old stand tended to be same or more than that of young stand. On the relationship between the stem biomass and the leaf and branch biomass which determines BEF, mean leaf and branch biomass of the stands with stem biomass less than 100 t ha^－1, 100 to 200 t ha^－1 and more than 200 t ha^－1 were 31.7 ± 6.6 t ha^－1, 36.4 ± 6.1 t ha^－1, 49.6 ± 9.5 t ha^－1, respectively. On the leaf and branch biomass of the stands with stem biomass more than 200 t ha^－1, there wasn't a tendency to increase with stem biomass. Although large branch biomass of old stand mitigates the decrease in BEF, the effect on BEF was limited. BEF of old stands with large stem volume seemed to be smaller than that of young stands.