Gaps and their natural disturbance characteristics in mid-subtropical evergreen broad-leaved forest in Wanmulin
中亚热带常绿阔叶林林隙及其自然干扰特征的研究

Through field investigation on 96 gaps in some permanent plots of mid-subtropical evergreen broad-leaved forest in Wanmulin Natural Reserve of Fujian Province, this paper dealt with the gap characteristics and their natural disturbance. The results showed that the area percentage of expanded gap (EG) and canopy gap (CG) in the forest landscape was 50.86% and 16.66%, and the natural disturbance frequency for EG and CG was 0.85% x yr(-1) and 0.28% x yr(-1), respectively. The return interval of canopy gaps was about 357 years. The most popular manner of gap formation in the forest was stem breakage (58.04% of the total), and the second was uprooting (33.48%). Most gaps were formed by two trees, averaging 2.33 trees per gap. The size of most expanded gaps was in the range of 100 - 300m2, the gaps of 200 - 300m2 occupied the biggest percentage in area, and those of 100 - 200m2 occupied the biggest percentage in number. The size of most canopy gaps was under 100m2, and the gaps of < 50m2 had the biggest percentage in area and number. The diameter at breast height of most gap makers was 20 - 30cm.