Abstract:

Through field investigation of 53 gaps in some permanent plots of virgin tropical montane rain forest in Bawangling nature reserve of Hainan island, this paper deals with gap characteristics and their natural disturbance regimes in tropical montane rain forest of Hainan island. Gaps in the tropical montane rain forest are elliptic in horizontal forms, the ratio of long axis/short axis for each gap is about 1.4. The area percentage of expanded gap(EG) and canopy gap(CG) in the forest landscape is 53.52 % and 25.22 % respectively. The natural disturbance frequency for EG and CG is 1.34 %·a^-1 and 0.63 %·a^-1 respectively, the return interval of canopy gaps is about 160 a. The size of most EG in the tropical montane rain forest range from 30 m² through 500 m², averaged about 160 m². And the size of most CG in the forest range from 15 m² through 200 m², averaged about 80 m². Most gaps were formed 40 years ago, and most of which aged 10~30 a. Most gaps were made by 1~4gap makers, of which two gap maker gaps are the majority. The percentage of different dead gap makers are as follow:uprooting 16.88 %, standing die 14.29 %, breakage at trunk base 36.36 % and breakage on trunk 32.47 %. Most gaps were formed by some combination of gap makers of different die manners. Major gap makers are about 20 tree species, in which there are not only tree species in the first canopy layer, but also tree species in the second and third layers. Finally, based on the study of gap dynamics in the tropical montane rain forest in Hainan island, some suggestions were made about management in the tropical montane rain forest.

Key words: Tropical montane rain forest, Gaps, Natural disturbance, Hainan island