Abstract: To test several important hypotheses on geographic diversity patterns of shrub communities in hyper-arid to semi-arid climates, including the water-energy dynamic hypothesis, the richness-productivity hypothesis, the freezing tolerance hypothesis, and the metabolic theory of ecology, the authors sampled 28 sites along an 1100 km transect across the shrub communities of Inner-Mongolia plateau, China. The climatic data and normalized difference vegetation index were used to examine whether community species richness could be well explained by different climatic factors or productivity. Different growth forms (shrub and herb) and different water ecotypes (xero-, mesoxero- and meso-plants) were also analyzed separately to examine how the richness-climate relationships differed among functional groups. It was found that species richness patterns for most ecological groups could be well explained by water-energy dynamic, the simultaneous availability of water and energy was critical in shaping shrub biome diversity patterns in the study area. Observed richness patterns were contrary to the prediction of the metabolic theory of ecology, suggesting that the hypothesis cannot explain diversity patterns in arid regions. The results also did not support the freezing tolerance, and showed that the richness-productivity hypothesis might be applicable for only some of the ecological groups (and thus the generality of this hypothesis was rejected). The response of species richness to climate or productivity gradient showed great differences among functional groups, suggesting that the ecophysiological characteristics of species and interspecific interactions have important influence on community richness patterns, in addition to climate and productivity. Understanding the community assembly rules may be critical for improving the ability to explain geographical diversity patterns.

Key words: climate, functional group, Inner Mongolia, shrub community, species richness

摘要： 为了验证几种重要的物种多样性地理格局假说(水分能量动态假说、生产力假说、寒冷忍耐假说、生态学代谢假说)在干旱、半干旱地区灌木群落中的适用性, 对内蒙古中西部地区1100 km样线内的灌木群落进行调查, 结合气候数据、植被归一化指数研究不同气候或生产力因子对群落物种丰富度的解释能力。同时研究了不同功能型的植物在物种多样性?气候关系方面的差异, 包括不同的生活型(木本、草本)、水分生态型(旱生、中旱生、中生)。结果表明: 1) 水分能量动态假说能较好地解释本研究区灌木群落多样性的地理格局, 植物能获得的有效水分是影响物种丰富度的主要因素; 2) 研究结果与代谢假说的预测相反, 该假说无法解释干旱、半干旱区的群落多样性格局, 结果不支持寒冷忍耐假说在研究区的适用性, 而生产力也只能解释部分功能型的物种丰富度; 3) 不同功能型的植物对气候、 生产力梯度的响应表现出很大的差异, 物种的生态特性以及种间相互作用对物种丰富度格局有着重要的影响, 深入理解群落的构建机制可能是理解生物多样性的地理格局所必需的。

关键词: 气候, 功能型, 内蒙古, 灌丛, 物种丰富度