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.
摘要:
青藏高原草地群落组成和结构的海拔梯度格局
青藏高原高寒草地是维持区域生态安全的天然屏障,也在一定程度上造就了该区域较高的生物多样性。然而,我们对青藏高原高寒草地植物群落组成和结构的海拔分布格局及其自身维持机制仍知之甚少。本研究在青藏高原东北部沿公路形成的海拔梯度设置了39个实验样地(海拔跨度为2800–5100m),每个样地设5个调查样方进行群落调查,包括物种组成、高度、盖度,评估青藏高原高寒草地植物群落的α和β多样性的海拔梯度格局及其影响因素。研究结果发现草地群落高度随着海拔的增加而显著降低,而群落盖度变化却不显著。随着海拔的增加,植物物种丰富度(α多样性)显著增加,而群落变异性(β多样性)显著降低。约束聚类分析表明,随海拔增加草地群落结构逐渐发生变化,基于此,在这种变化过程中,我们监测到3个渐变的海拔间断点,分别在海拔3640、4252和4333 m处。结构方程模型(SEM)表明,降水增加和温度降低对α多样性有显著的正向作用,但植物群落α多样性的变化显著改变群落变异性。以上结果表明,青藏高原的群落组成和结构沿海拔梯度发生了从量变到质变的过程。
关键词:
α多样性,
β多样性,
海拔梯度,
青藏高原,
海拔间断点