晋西黄土高原天然次生林木本植物垂直分布格局

Patterns of Tree Species Composition of Secondary Natural Vegetation along an Altitudinal Gradient on Earthy-rocky Mountainous Area in Western Shanxi Province

对晋西黄土高原土石山区天然次生林乔灌层优势种组成及其多样性进行了研究,结果表明:木本植物优势种组成受海拔梯度影响明显,丰富度沿海拔梯度升高而呈下降趋势,总体上灌木的丰富度比乔木高,且乔木树种与灌木树种丰富度的变化规律存在明显差异,乔木树种在海拔较高地段丰富度较大,而灌木树种则是在海拔较低地段丰富度较大;乔木层α多样性指数随海拔升高而递增,而灌木层α多样性指数则随海拔升高呈缓慢下降趋势。采用Cody指数和Whittaker指数计算了各海拔群落的β多样性指数,得出各海拔群落的β多样性指数多以相邻海拔群落的指数值最小,群落间海拔差异越大指数值越大,其中在海拔高度1 650 m左右β多样性指数变化最为显著。

The patterns of dominant species and ligneous plant community diversity was analyzed at different altitudinal gradients in the earth-rocky mountainous area in western Shanxi Province. The result are as follows： the dominant species had regular change in different altitudinal gradients ; the species richness of all the ligneous plants decreased with the increment of altitude. The tree species richness was high in the community of high altitude, but the shrub species richness was high in the community of low altitude. In most altitude the richness of shrub species was greater than that of arbor species. The α diversity of arbor layers was big in high altitude, however the α diversity of shrub layer decreased with the increment of altitude. In the β diversity research, the Cody index and Whittaker index were studied in the communities of this region. The result indicated that the β diversity index was low among the communities of neighboring altitude, but the index increased when the distance was high between the communities. The result showed the value of β diversity indices was maximal in the region of about 1 650 m altitude.