典型草原大针茅种群空间格局及对长期过度放牧的响应

种群空间格局是生态学研究的基本问题之一。典型草原带由于过度放牧退化严重, 原生群落罕见, 探讨原生群落的种群空间格局具有重要生态学意义。大针茅(Stipa grandis)草原是典型草原区广泛分布的主要群落类型, 1979年围封的大针茅样地, 是目前保存完整的大针茅草原原生群落。本文选择大针茅草原原生群落和长期过度放牧群落, 应用O-Ring函数结合不同零假设模型分析了大针茅种群的空间格局。结果表明: 在原生群落中大针茅种群在小尺度范围内呈均匀分布, 而在长期过度放牧群落中则表现为聚集分布。这说明在大针茅草原原生群落中竞争是主要的相互作用, 而在长期过度放牧群落中正相互作用居主导, 验证了胁迫梯度假说; 同时证明长期过度放牧改变了种群空间格局。

Population spatial pattern of Stipa grandis and its response to long-term overgrazing

Spatial distribution patterns of plant populations is fundamental to ecology. Primary communities have become rare in the steppe because long-term overgrazing has led to serious degradation of the steppe ecosystems and requires further investigation. The most widely distributed grassland across the Eurasia steppe region is the Stipa grandis community. At present, there are well-preserved primary S. grandis communities in the steppe region. We chose the primary S. grandis community and long-term overgrazing community of S. grandis, and applied an O-Ring function combined with null models to analyze the spatial pattern of S. grandis. The results showed that the spatial pattern of S. grandis was overdispersed in the primary community at the small scale, while it was clustered in the long-term overgrazing community. These results indicate that competition was the main interaction in the primary community, while positive interactions dominated in the long-term overgrazing community. Therefore, these results verified the stress gradient hypothesis and proved that long-term overgrazing altered population spatial patterns.