Changes in forest structure and composition on Changbai Mountain in Northeast China

Introduction Long-term ecological studies are essential for understanding the dynamics of natural systems. However, describing long-term dynamics in old-growth forests is often hindered by a lack of archival data. Methods In this study, we investigated (1) changes in forest structure and tree species composition and (2) population dynamics of the dominant tree species over a 29-year period (1981-2010) in two old-growth forests with stand ages exceeding 200 years on Changbai Mountain in Northeast China. Results Results showed that the stem density of the broad-leaved/conifer mixed forest at 740 m asl increased slightly from 510 to 515 trees per hectare and the total basal area increased significantly from 36.19 to 46.53 m(2) ha(-1), suggesting that the forest was still maturing over the study period. However, the coniferous forest at 1,680 m asl displayed structural changes in the form of a significantly decrease in both stem density and total basal area over the study period. No changes in tree species composition in the two forests were observed. Discussion Wind was considered to be a frequent natural disturbance affecting the forest structure and dynamics, especially for the coniferous forest at the higher altitude. Dominant tree species in the two forests exploited different biological characteristics in maintaining their respective populations.