人为干扰对碧峰峡栲树次生林群落物种多样性及其优势种群生态位的影响

为进一步了解人为干扰对碧峰峡生态旅游区的生态环境及不同种群利用资源、占据生态空间的能力的影响,并为该区植物资源、大熊猫栖息地的保护及旅游可持续措施的制定提供依据,调查了人为干扰下碧峰峡栲树(Castanopsis fargesii)次生林物种多样性及其优势种群生态位的组成情况。结果表明:7200m2的样方中共记录到156个植物种,隶属于70科114属,其中乔木16科23属33种,灌木39科67属95种,草本38科42属47种;乔木层总体物种多样性水平在中度干扰下最低,在轻度及重度干扰下差异不大。灌木层总体物种多样性水平在中度干扰下最高,在轻度干扰下最低。而草本层物种多样性随着干扰强度的加深有明显降低趋势;随着人为干扰强度的增加,乔木层中优势种栲树的生态位宽度均为最大,与其他树种生态位重叠值在中度干扰下有所降低,枹栎(Quercus serrata)的生态位宽度会变小,山茶科(Theaceae)植物的生态位变宽,同时其生态位重叠值增大;在灌木层中,重度干扰下,菝葜(Smilax china)生态位宽度减小,栲树幼苗的生态适应范围也骤减,其他大多数物种在中度干扰下,生态位宽度最低;在草本层中,蕨类植物及皱叶狗尾草(Setaria plicata)在重度干扰下生态位宽度及重叠值均增高,其适应范围变广,种间竞争加剧。综合分析表明,群落各层次物种多样性水平对人为干扰的响应各不相同,其中人为干扰对灌木及草本层物种多样性影响最大。同时人为干扰会改变群落物种组成及种间原有的关系,特别是中度干扰会使群落间优势种地位增强,种间竞争关系加剧,导致其原有生境被破坏,不利于群落发展。因此强化景区保护及合理经营迫在眉睫。

Effects of anthropogenic disturbances on the species diversity and niche of the dominant populations in a Castanopsis fargesii secondary forest community in Bifengxia, Sichuan

To further understand the effects of anthropogenic disturbances on the ecological environments and on the ability of resources utilization and ecospace occupation of the dominant population in the ecotourism area of Bifengxia, we investigated the effects of anthropogenic disturbance on the species diversity and niche of the dominant population in a Castanopsis fargesii secondary forest in this area. The results showed that a total of 156 species belonging to 70 families and 116 genera were found in a 7200 m² quadrat. Specifically, there were 33 tree species from 16 families including 23 genera, 95 shrub species from 39 families including 67 genera, and 47 herbaceous species from 38 families including 42 genera. The level of species diversity in arborous layer was lowest under intermediate disturbance, and no obvious difference was found between communities under slight and severe disturbance. However, species diversity level in shrub layer was highest under intermediate disturbance, and lowest under slight disturbances. An obvious decrease for the level of species diversity was found in the herbaceous layer. With increase in the strength of disturbance, the niche breadth value for the dominant species (C. fargesii) in arborous layer was consistently the highest, and the value overlapping with other species decreased at certain degree under intermediate disturbance. The niche breadth value for Quercus serrata decreased, but such value for Theaceae increase as well as the overlapping value. In the shrub layer, the niche breadth value for Smilax china decreased under severe disturbance, as well as C. fargesii seedings. The niche breadth values for the majority of other species were lowest under intermediate disturbance. In the herbaceous layer, the niche breadth values and overlap values for Pteridium aquilinum var. latiusculum and Setaria plicata both increased under severe disturbance, with wider adaptive range and intensifying interspecific competition. The results suggest that anthropogenic disturbances have significant impacts on the species diversity, species status in community, and interspecific relationship in the C. fargesii secondary forest, indicating urgent measures in ecological protection and appropriate management.