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β多样性度量群落物种组成随环境梯度的变化程度。为了了解地理距离和地形差异在连续空间中对β多样性的影响,本文比较研究了地形复杂的我国古田山24 ha亚热带常绿阔叶林样地和地形平坦的巴拿马Barro Colorado Island(BCI)50 ha热带森林样地植物群落的β多样性及其形成机制,在不同取样粒度(grain)上分析了地理距离和地形差异对β多样性的影响。我们采用1–Chao-Jaccard指数作为β多样性的度量指标,然后用Mantel和Partial Mantel等检验来分析地理距离、地形以及5种地形因子单独对β多样性的影响。结果表明,两个样地中群落的β多样性均具有粒度依赖性:粒度越大,β多样性越小;同时,两样地β多样性均受到距离和地形的显著影响,且随着粒度的增大,群落β多样性与距离的相关性呈相似的单调递增趋势。另外,地形对较复杂的古田山样地各粒度上植物群落β多样性的影响均较大,且主要由海拔和凹凸度两个因素造成;而地形对较平坦的BCI样地植物群落β多样性的影响则较小。本研究结果提示,生态位过程和扩散过程都是形成β多样性的重要机制。
β diversity measures the degree of community composition change with environmental gradients. In order to understand the effect of geographical distance and topography on β diversity in continuous space, this paper comparatively studied the topography of the 24 ha subtropical evergreen broad-leaved forest in Gutian Mountain and the flat Barro Colorado Island (BCI) 50 β diversity and its formation mechanism of plant communities on tropical forest plot, the effect of geographical distance and topography on β diversity was analyzed on different sampling grain sizes. We use the 1-Chao-Jaccard index as a measure of β-diversity, and then use the Mantel and Partial Mantel tests to analyze the effects of geographic distance, topography, and the five topographic factors alone on β-diversity. The results showed that the β diversity of the communities in the two plots were all grain-dependent: the larger the grain size, the smaller the β diversity; the same, the two β diversity were significantly affected by the distance and the topography, and with the size Increasing, the community β diversity and distance correlation showed a similar trend of monotonous increase. In addition, the influence of terrain on the β diversity of plant community in each of the more complex Gutian Mountain plots was greater, and was mainly caused by two factors: elevation and concavity; The impact of sex is smaller. The results of this study suggest that both the niche process and the diffusion process are important mechanisms for the formation of β diversity.