紫楠天然群落物种多样性对不同干扰强度的响应

以紫楠Phoebe sheareri全分布区内20个典型天然群落为研究对象，通过分析群落物种组成、植物区系类型、物种多样性水平，研究紫楠群落物种多样性对不同干扰强度和气候条件的响应。结果表明:10 400 m2的调查样地内共计维管束植物103科236属363种，种子植物科、属区系类型丰富，以北温带、泛热带成分为主；干扰强度和气候条件共同作用，影响紫楠群落物种多样性，物种丰富度Patrick指数、多样性Shannon-Wiener指数、优势度Simpson指数和均匀度Pielou指数均表现出差异。处于5级干扰的绿荷塘群落，紫楠在乔木层占绝对优势，而在灌木层处于次优势地位，且整体多样性水平低，不利于该群落的可持续发展；乔木层Patrick指数、Shannon-Wiener指数与干扰强度呈显著相关，即干扰越强，群落乔木层物种丰富度与多样性程度越低；灌木层Shannon-Wiener指数、Simpson指数、Pielou指数的最大值都出现在2级干扰时，说明中等强度的干扰对灌木层物种多样性具有促进作用。相比气候条件，干扰强度对紫楠群落物种多样性的影响更大。

Species diversity of natural Phoebe sheareri communities with different disturbance intensities

Due to the enhancement of disturbance, the natural communities of Phoebe sheareri, a precious species peculiar to China and one of the original species for the commercial timber production of "Nanmu with golden tint", being scattered in some provinces and regions to the south of the Yangtze River, were studied. All 20 typical natural communities of P. sheareri in sample plots within 10 400 m2 of its distribution area were analyzed for responses of species diversity to different disturbance intensities and climatic conditions. Analyses of species composition, flora, and species diversity were based on the Patrick index for abundance, Shannon-Wiener index for diversity, Simpson index, and Pielou index for evenness. Results showed a total of 363 vascular species belonging to 236 genera of 103 families. Both genera and families of seed plants were abundant, but were mainly from north temperate and pan-tropical areas. Differences in the Patrick, Shannon-Wiener, Simpson, and Pielou indexes showed that both disturbance intensity and climatic conditions co-acted on the species diversity of P. sheareri-containing communities. With a disturbance of Grade Ⅴ, P. sheareri was absolutely dominant in the tree layer of the Lühetang Community, but was in a sub-dominant position in the shrub layer with a low diversity on the whole, which meant it was unfavorable for sustainable development. Disturbance intensity was found to be significantly correlated with the Patrick index (P=0.006, r=-0.643) and Shannon-Wiener index (P=0.037, r=-0.045)with a stronger disturbance having a lower species abundance and diversity in the tree layer. Also, the highest values of the Shannon-Wiener index, Simpson index, and Pielou index in the shrub layer occurred when there was a disturbance of Grade Ⅱ, meaning that an intermediate disturbance promoted species diversity in the shrub layer. Overall, P. sheareri was suitable for coexistence with many other plant species to form a community, and the disturbance intensity had more influence on species diversity in the P. sheareri community than climatic conditions.