Effects of dwarf bamboo on the regeneration of dominant tree species in gaps of subalpine dark coniferous forest

The effects of gap size and dwarf bamboo coverage on the regeneration of subalpine dark coniferous forest were examined in Wolong Giant Panda Nature Reserve,Sichuang Province. The gaps (≤50 m2,50-150 m2 and150 m2) were selected, there are 3 dwarf bamboo coverage (20%,20%-50% and50%) in each gap area type,and three contrasting understory bamboo cover conditions (≤20%,20%-50% and50%) were contained in the same sized gaps,as well. The results showed that:(1)no matter what gap area,the number of tree seedlings in gaps was more than that in understory,gap regeneration is the primary approach of the community regeneration of Abies faxoniana; (2)the gaps which we selected were all at early phase,so the specific composition and quantity of seedlings among every gap are obviously different. The seedlings and saplings abundance of Betula utilis increased with gap enlarged,and this demonstrated that it needed larger gaps to regenerate than Abies faxoniana; (3)there were significant differences in number of seedlings among the gaps with different bamboo coverage,and dense bamboo evidently impeded the forest regeneration process; (4)with the increasing of gap size,the degree of dispersion of Fargesia nitida decreased,and average height and basal diameter tended to increase.