华西箭竹对卧龙亚高山森林不同演替阶段物种多样性与乔木更新的影响

比较阔叶林、针阔混交林与针叶林有竹与无竹环境下的物种多样性与更新状况.结果表明:华西箭竹的存在未改变森林演替过程中多样性的变化趋势,但降低了各阶段物种多样性,尤其对灌木层多样性的影响最为显著,对阔叶林物种的影响大于针叶林;与无竹环境相比,华西箭竹环境下林分各层物种丰富度都有所降低,灌木层的均匀度和多样性明显下降,但对草本层影响较小;阔叶林、针阔混交林与针叶林无竹环境乔木幼苗数量大于华西箭竹环境,箭竹环境光资源较差且枯落物较厚,不利于幼苗萌发与生长;糙皮桦幼苗及各径级树木在阔叶林无竹环境数量最多,而岷江冷杉在针叶林无竹环境最多,但在箭竹环境也有一定数量;华西箭竹的存在阻碍了糙皮桦的高生长,但对冷杉的影响较小,因此,华西箭竹的存在加速了糙皮桦的更新失败,同时也阻碍了冷杉的更新进程.总之,亚高山森林内华西箭竹的存在,降低了森林循环演替各阶段的物种丰富度与多样性,同时也不利于森林演替过程中乔木的更新.

Effects of Fargesia nitida on Species Diversity and Trees Regeneration in Different Forest Cycles of Subalpine Forest in Wolong Nature Reserve

To understand the effects of Fargesia nitida on forest cycle succession of subalpine forests in Wolong Nature Reserve, Sichuan Province, species diversity and tree regeneration with bamboo(B~+) and without bamboo(B~-) condition of three regeneration stages were investigated. The results showed: The F. nitida could not change the trend of diversity dynamics but had negative effect on diversity in the process of forest cycle succession, especially on the diversity of shrub layers, and species in broadleaved forest(BF) influenced by F. nitida was more significant than those in dark coniferous forest(CF). In comparison with B~-, species richness of all layers were declined, evenness and diversity of shrub layers were sharply decreased in B~+ of three stages. Seedlings in B~- were more abundant than in B~+ conditions of three stands as low light and thick litters in B~+ were disadvantage for seedlings germination and growth. The number of Betula utilis individuals was most in B~- of BF, and that of Abies faxoniana was most in B~- of CF, there were still some in B~+ of CF. F. nitida also impeded height growth of B. utilis, but had little effect on A. faxoniana, therefore, regeneration fail of B. utilis was accelerated and regeneration process of A. faxoniana was hindered by F. nitida. In conclusion, species richness and diversity of different stages were declined and tree regeneration was restricted by occurrence of F. nitida in forest cycle succession of subalpine forest.