2015 Volume 57 Issue 1 Pages 33-42
To assess the community structural change and to document temporal trends in biomass accumulation of an old-growth forest over a period of 17 years, we surveyed the forest structure and tree diameter in a 1-ha plot established in a cool-temperate deciduous forest on the eastern slope of Mt. Hakusan in 1995 and 2012. In a stand dominated by Fagus crenata (beech) and Quercus mongolica var. crispula (oak), the largest diameter at breast height (DBH) in 2012 was 100.3 and 194.7 cm, respectively. Although the tree density (DBH ≥ 5 cm) increased from 908 to 940 stems ha^<-1> from 1995 to 2012, nine large dead trees were found in this period. Because of dead canopy trees, the gap enlarged and a change in the forest structure occurred in the tree and subtree layers according to mean tree weight-weight of individual trees (M-w) diagrams. The forest biomass was estimated to be 537.8 and 536.7 t ha^<-1> for 1995 and 2012, respectively. The biomass in this forest was extremely high compared with those in old-growth beech forests studied elsewhere in Japan because of the existence of some huge oak trees. The loss of biomass (73.7 t ha^<-1>), partly because of large dead oak trees, was compensated by the growth of beech. Thus, the change in biomass in the 17-year period was very small. The results of the present study indicated that this old-growth beech-oak forest showed nonequilibrium in forest community dynamics; however, the forest biomass was at a steady state.
