Bai Y, Xing X, Xu Z, Li D
Institute of Botany, Chinese Academy of Sciences, Beijing 100093.
Ying Yong Sheng Tai Xue Bao. 2000 Jun;11(3):408-12.
The beta-diversity characteristics of four Stipa communities (S. baicalensis, S. grandis, S. krylovii and S. klemenzii) were studied using comparable plots methods. As a measurement of species turnover within communities, Whittacker's index(beta ws) was size-dependent, and reduced gradually with the increasing quadrat size. Under the same scale, beta ws indices of the communities were similar. Cody's index (beta c) was also affected by sampling size. beta c increased initially as quadrat size enlarged, then stabilized over the size of 0.5 m2 for S. baicalensis and S. grandis communities, and 2 m2 for S. krylovii and S. klemenzii communities. S. baicalensis community had the highest Cody index, while S. klemenzii community had the lowest one. In most cases, the within-community distance interval had a relatively high effect on Cody index; From S. baicalensis to S. klemenzii community, the functional group diversities of forbs, perennial bunch and rhizome grasses decreased greatly, the diversity of intermediate xerads reduced significantly, and the diversity of xerads increased firstly, and then declined for S. klemenzii community. The changes in species composition of four Stipa communities could give a reflection to the degrees of community replacement along ecological gradients, and Cody indices between the communities reduced gradually. The Morisita-Horn similarity coefficient between S. baicalensis and S. grandis community was significantly higher (0.72) than those between S. grandis and S. krylovii communities (0.55), and between S. krylovii and S. klemenzii communities(0.42).
采用可比样地法研究了4种针茅群落（贝加尔针茅、大针茅、克氏针茅和冷蒿）的β多样性特征。作为群落内物种周转的一种度量，Whittacker指数（βws）与样方大小有关，且随着样方大小的增加而逐渐降低。在相同尺度下，各群落的βws指数相似。Cody指数（βc）也受采样大小的影响。随着样方大小的增大，βc指数起初增加，然后对于贝加尔针茅和大针茅群落，在样方大小达到0.5 m²时趋于稳定，对于克氏针茅和冷蒿群落，在样方大小达到2 m²时趋于稳定。贝加尔针茅群落的Cody指数最高，而冷蒿群落的Cody指数最低。在大多数情况下，群落内距离间隔对Cody指数有较高影响；从贝加尔针茅群落到冷蒿群落，杂类草、多年生丛生禾草和根茎禾草的功能群多样性大幅降低，中生旱生植物的多样性显著降低，旱生植物的多样性先增加，然后在冷蒿群落中下降。四种针茅群落物种组成的变化能够反映群落沿生态梯度的替代程度，且群落间的Cody指数逐渐降低。贝加尔针茅和大针茅群落之间的Morisita-Horn相似系数（0.72）显著高于大针茅和克氏针茅群落之间的相似系数（0.55），以及克氏针茅和冷蒿群落之间的相似系数（0.42）。
