五鹿山国家级自然保护区物种多样性海拔格局

Altitudinal pattern of plant species diversity in the Wulu Mountain Nature Reserve,Shanxi,China

在五鹿山国家级自然保护区典型地段设立样地,以植物群落样地调查数据为基础,计算不同层次的多样性指数,运用广义可加模型分析各物种多样性的海拔格局。结果表明:乔木层的胸高截面积沿海拔呈显著递增趋势(P<0.05);α多样性,乔木层丰富度指数、香浓维纳指数、均匀度指数都呈显著的单峰分布格局(P<0.01),灌木层丰富度指数、香浓维纳指数大体呈以中高海拔1507m为峰值的偏峰分布格局,均匀度指数大体呈显著递增趋势(P<0.05),草本层丰富度指数、香浓维纳指数较低海拔下随海拔升高递减,较高海拔下变化不大,均匀度指数大体呈递增趋势;β多样性大体呈"～"型变化;γ多样性,大体呈单峰分布格局。沿海拔梯度升高,水热组合发生变化,地带性植被以及群落内的建群种和优势种都发生了变化。

Wulu Mountain Nature Reserve is located between the western margin of the North China Plain and the eastern margin of the Loess Plateau, and shows distinct transitional vegetation types and high species richness. Thus the reserve has an important role to play in plant biodiversity research. In the present study we investigated the plant species distribution along an altitudinal gradient in the Wulu Mountain Nature Reserve in October, 2010. The vegetation zones and dominant species in each community changed with increasing elevation, and a combination of rainfall and temperature determined the major communities in the forests. The plant communities were classified as Robinia pseudoacacia forest, Pinus bungeana forest, mixed conifer-broadleaf forest, and Quercus liaotungensis forest. We investigated the species composition of plant communities in different plots to discern patterns of species diversity and distribution along the altitudinal gradient. We calculated α-diversity,β-diversity and У-diversity using the data collected from the study plots and analyzed with a generalized additive model to examine the following relationships ： 1 ） changes in the total number of trunks and diameter at breast height in all forest plots along the altitudinal gradient; 2） species richness in the tree, shrub and herbaceous layers with altitude; 3） the Shannon-Wiener diversity index for the tree, shrub and herbaceous layers with altitude; 4） Pielou＇s evenness index for the tree, shrub and herbaceous layers with altitude; 5 ）β-diversity for the tree, shrub and herbaceous layers with altitude; 6） T-diversity with altitude; and 7 ） the relationships of grass species richness with total number of trunks and diameter at breast height in all forest plots. The results showed that total number of trunks and diameter at breast height in all forest plots increased with the increase in elevation. Species richness, the Shannon-Wiener diversity index and Pielou＇s evenness index for the tree layer were significantly higher in mixed conifer-broadleaf forest at middle elevations （P〈0.01）. Species richness and the Shannon-Wiener diversity index of the shrub layer both peaked at 1507 m but were also relatively high at 1160 and 1260 m, whereas Pielou＇s evenness index of the shrub layer increased with the increase in elevation （P 〈 0.05）. In contrast, species richness and the Shannon-Wiener diversity index of the herbaceous layer decreased with the increase in elevation except at lower elevations, owing to the significant influence of forest canopy cover, whereas no differences in species richness and the Shannon-Wiener diversity index of the herbaceous layer were observed at higher elevations. Pielou＇s evenness index of the herbaceous layer increased with the increase in elevation. The ShannonWiener diversity index over the entire altitudinal gradient showed the rank order： herbaceous layer〉shrub layer〉tree layer. Beta-diversity showed peaks at middle and high elevations. Gamma-diversity was highest at 1400--1500 m altitude. Aridity at low altitudes and low temperature at high altitudes limited species survival, and only middle elevations experienced favorable precipitation and temperatures to support high plant species diversity. The species richness of grasses decreased with the increase in total number of trunks and diameter at breast height in all forest plots.