荒漠植被植物种多样性对空间尺度的依赖

物种多样性与空间尺度的关系是植物生态学的一个研究热点。传统植物生态学研究认为种面积曲线方程中 Z值是个近似常数 ,但近期对森林和草原群落的研究表明 Z是随尺度变化的。在荒漠带选择了 10个样地 ,每个样地包括 1m2 到 1km2 的 6个空间尺度样方 ,研究荒漠地区物种多样性与空间尺度的关系。结果表明 :荒漠植被物种多样性随空间尺度的增大空间依赖性减弱 ,Z也是随尺度变化的。对荒漠植被种面积曲线 Z的研究结果支持了 Z随尺度变化的结论 ,但 Z是随尺度增加而减小 ,斜率 z值从 0 .37降至 0 .0 35 ,与草原和森林群落 Z值随尺度增加而增加的结论是相反的。

Scale dependence in desert plant biodiversity

The relationship between the number of species and the area sampled is one of the oldest and best-documented patterns in community ecology. Species-area relationships have been widely used to examine the latitudinal gradient in species diversity, the effect of habitat loss on species diversity and the impact of exotic species on species diversity. An equation of the form S=cA~z describing more precisely the species-area relation for plant species in smaller area is proposed as a result of intensive examination of species presence. Several studies and field data from a wild range of plant and animal taxa suggest that the slope, z, of a graph of the logarithm of species richness against the logarithm of area is not a constant to the grassland and forest communities. This study was conducted to examine which the characteristic of species diversity of desert community and the change laws of z with spatial scales variance are appropriate for inference which z is not a constant, and the other purpose of this paper was to reveal the distinction of species diversity between desert community and grassland or forest community.We collected replicated and randomized plant data at 6 spatial scales from 1 m~2, 10 m~2, 100 m~2, 1000 m~2, 10000 m~2 to 1 km~2 in the desert region of west China. The results showed that the slope of the log-log plot varied systematically with spatial scale, the value of z was high (0.37) at small scales from 1m~2 to 10 m~2, but it decreased with spatial scales increasing. When spatial scales varied from 1m~2 to 1 km~2, the value of z varied from 0.37 to 0.035. Furthermore, when the replication at each scale is used (in a log-linear model corrected for over dispersion), it was found that highly significant differences in slope from scale to scale, for example, at small scales from 1m~2 to 100 m~2, regressions of log (species richness) against log (area) gave slope of 0.273 (SE=0.087), but at larger scales from 100 m~2 to 1 km~2, the value of slope was 0.0396 (SE=0.0039). These results described that species richness of desert community at small scale (less than 100m~2) had strongly scale dependence, and were different from the research of grassland and forest communities. They directed attention to the need to develop a more mechanistic understanding of patch patterns and coexistence at small scales in the desert community.