运用β多样性探讨不同更新模式对米槠群落高度级和物种多样性的影响

运用β多样性研究了不同更新模式（择伐更新、天然更新和人工更新）对米槠Castanopsis carlesii（Hemsl．）Hayata]群落高度级和物种组成的影响。结果表明：更新前各米槠林样地均有7个高度级，cody指数（βc）和共有种数随高度级增大迅速减小；更新期各样地的高度级均减少，但随更新期延长高度级有所增加，低（第1至第3）高度级的物种数也有所增加。物种周转主要发生在第1至第3高度级。更新前各样地低（第1至第3）高度级间非共有种数和共有种数均较多，相异性系数较小并随高度级差异增加而增大；但受到干扰（皆伐）后相异性系数急剧增大并呈现先增大后减小的规律。择伐更新导致米槠群落高度级减少但可逐步恢复；天然更新样地中米槠生长很快，在12年更新期内已进入第6高度级；人工更新样地中米槠已不能生存，人工种植的杉木Cunninghamialan ceolata（Lamb．）Hook．]成为优势种。总体上看，采取不同的更新模式后米槠群落的物种多样性变化明显，但择伐更新和天然更新属轻、中度干扰，有利于群落物种多样性的维持和稳定；而人工更新为重度干扰，导致群落基准高度级物种周转速率和总物种周转速率均大幅下降，使群落演替方向大幅改变。

Effect of different regeneration modes on height class and species diversity of Castanopsis carlesiicommunity by using βdiversity

Effects of different regeneration modes （selective cutting regeneration, natural regeneration and artificial regeneration ） on height class and species composition of Castanopsis carlesii （Hemsl.） Hayata community were studied by means of β-diversity. The results show that there are seven height classes in all plots of C. carlesii woods before regeneration, and Cody index （βc） and number of common species decreases rapidly with increasing of height class. During regeneration period, number of height class decreases, but with prolonging of regeneration time, number of height class increases and species number in low （the first to the third） height class also increases. And species turnover mainly occurrs at the first to the third height class. Before regeneration, numbers of both non-common species and common species are more at low （the first to the third） height class in all plots, and dissimilarity index is smaller and increases with increasing of height class difference. But after getting a disturbance （ clear-cutting）, dissimilarity index increases sharply and appears a law of first increasing and then decreasing. Selective cutting regeneration causes decreasing of height class of C. carlesii community but the decreasing can be recovered gradually. In natural regeneration plot, C. carlesii grows very quickly and can reach into the sixth height class during twelve years. While in artificial regeneration plot, C. carlesii can not survive and Cunninghamia lanceolata （Lamb.） Hook. artificially planted becomes dominant species. Generally,the change in species diversity of C. carlesii community is obvious after taking different regeneration modes. But selective cutting regeneration and natural regeneration are mild and moderate disturbances, respectively and beneficial to maintenance and stability of community species diversity. While artificial regeneration is a serious disturbance and can cause the remarkable decrease of species turnover rate of base height class and total species turnover rate of community, and greatly change the direction of community succession.