关键词: α多样性, β多样性, 海拔梯度, 青藏高原, 海拔间断点

Abstract:

Grasslands in the Qinghai–Tibet Plateau play an important role in preserving ecological security and high biodiversity in this region. However, the distribution of the composition and structure of plant community and the mechanism by which it maintains itself in this region are still poorly understood. Here, we designed 195 grassland plots in 39 grassland sites along an approximately 1700 m elevation gradient on the Northeastern Qinghai–Tibet Plateau. We found that the grassland community height decreased significantly with increasing elevation, whereas community coverage did not significantly change. With increasing elevation, plant species richness (α diversity) increased significantly, but the community variability (β diversity) decreased significantly. The constrained clustering analysis suggested that the α- and β-diversity in the grasslands transformed gradually with elevation, and that three discontinuous points (based on community structure) were observed at elevation of 3640, 4252 and 4333 m. Structural equation modeling (SEM) indicated that the increase in precipitation and the decrease in temperature significantly positively influenced α diversity, which was negatively correlated with β diversity. These results demonstrate a quantitative-to-qualitative change in the community composition and structure along this elevational gradient on the Qinghai–Tibet Plateau.

Key words: alpha diversity, beta diversity, elevational gradient, Qinghai–Tibet Plateau, discontinuous points