关键词: 气候, 功能型, 内蒙古, 灌丛, 物种丰富度

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