小径竹对亚高山暗针叶林优势 树种林窗更新的影响

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

关键词:  小径竹  林窗  更新  岷江冷杉  幼苗

Key words:  dwarf bamboo  gap  regeneration  Abies faxoniana  seedling

摘要:

在亚高山岷江冷杉林中选取面积≤50 m²,50～150 m²,>150 m²的林窗,每种类型内均包含3种小径竹盖度(≤20%、20%～50%、>50%),共调查林窗9个,并调查包含这3种小径竹盖度的三块林下对照样地,研究了该类森林林窗更新与小径竹生长的关系。结果表明:(1)无论林窗大小,林窗内的更新幼苗数量都比林下的多,林窗更新是岷江冷杉群落更新的主要途径;(2)所选林窗均为发育早期,林窗对更新树种的种类组成和数量的影响主要表现在幼苗上。糙皮桦幼树及幼苗数量随林窗面积的增加而急速增加,它的更新更需要较大的林窗;(3)不同小径竹盖度下幼苗的密度呈现显著性变化,小径竹的生长明显抑制了森林幼苗的更新及填充的进程;(4)华西箭竹的分散程度随林窗面积的增大而降低,而平均高度和基径则有增加的趋势。

Abstract:

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 and>150 m²)were selected, there are 3 dwarf bamboo coverage(20%,20%-50% and>50%)in each gap area type,and three contrasting understory bamboo cover conditions(≤20%,20%-50% and>50%)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.