铜壁关自然保护区种子植物物种丰富度的海拔梯度格局——兼论物种密度的计算方法

利用对铜壁关自然保护区多次考察形成的种子植物数据库,结合通过GIS生成的区域数字高程模型(DEM)数据,分析了该区域种子植物物种丰富度及物种密度沿海拔梯度的变化特征。结果表明, 科、属、种的丰富度随海拔的升高,先增加后降低,在中海拔区域达到最大值,科、种的丰富度最大值出现在海拔1400~1800 m的范围内,属的丰富度最大值出现在1000~1400 m的海拔范围。科、属、种的密度随海拔升高先下降后上升,再下降后再上升;且最大值都出现在保护区最高海拔3000~3400 m的范围内。物种丰富度和物种密度分布格局明显受到海拔梯度的影响,海拔梯度综合了水热条件等诸多因素。铜壁关种子植物科、属、种水平上的物种丰富度的海拔分布格局符合中域效应假说;同时还对目前常用的计算物种密度的"对数模型"方法的普遍适用性提出质疑。

Pattern of Species Richness along Altitudinal Gradient in Tongbiguan Nature Reserve, Southwest China and with A Discussion on Calculation Methods of Species Density

The altitudinal gradient patterns of richness and species density of seed plants and their relationship with topographic parameters on Tongbiguan Nature Reserve in Southwest China were studied. The database of seed plants including their distribution ranges was constructed by field investigation many times, and the DEM (Digital Elevation Model) was derived from a topographical map of this region. The results showed that the species, genus and family richness increased rapidly at first and then decreased with the elevation increment, and those reached up to the maximum at middle altitude regions. The maximums of species and family richness appeared at the altitudes between 1400 m and 1800 m, and that of genus richness at the altitudes between 1000 m and 1400 m. When the area factors were eliminated, the taxa density decreased and increased firstly, then decreased and increased finally with the increment of elevation, up to peaks at the altitudes between 3000 m and 3400 m. The distribution patterns of species richness and species density were affected by the elevation gradient significantly which integrated many factors, such as moisture and energy conditions and so on. The altitudinal patterns of species richness at family, genus and species levels were consistent with the mid-domain effect hypothesis. It was took a question of "Logarithmic Model" in the calculation of the species density which was commonly used in the research of biodiversity at present.