Study On The Niche Of Dominant Shrub Population In West Ordos And East Alashan Desert

Inner Mongolia west Ordos-east Alashan region was one of the important regions in biodiversity. It's a refuge of relic-endemic plant in ancient Mediterranean Sea. Many ancient relic species centrally distributed in this area, most of them were the constructive or dominant species of desert community, and their existence played an important role in maintaining fraigle ecosystem. In this thesis, we chose Tetraena mongolica, Helianthemum soongoricum, Potaninia mongolica, Ammopiptanthus mongolicus, Reaumuria soongorica and Zygophyllum xanthoxylon as study objects. Then, we discussed these population interspecific competition and resource utilization through the theory and formula of niche in the dimensions of Terrain, Weather and Soil. Following were the results:The result was mostly the same that was measured by using Levin's formula and Smith's formula respectively. The result using coverage value as index was more objective than using unit as index.The niche breadth of Reaumuria soongorica population was the greatest of all the species investigated. This demonstrated that the adapting environment and utilizing resource ability of Reaumuria soongorica was very strong. Potaninia mongolica, Ammopiptanthus mongolicus, Zygophyllum xanthoxylon have strong ability of adaptation to environment and using resources. They can be dominant populations in well environmental condition. Tetraena mongolica and Helianthemum soongoricum required strict request and special choice for environment factors. They had narrow niche and often came into being concentrated populations.The niche overlap value among those species with wide niche breadth like Potaninia mongolica, Ammopiptanthus mongolicus, Reaumuria soongorica and Zygophyllum xanthoxylon was significant and they had high niche similar index. So there was strong competition in environmental requirements and resource use. Tetraena mongolica and Helianthemum soongoricum had narrow niche breadth, but their niche overlap value was still significant. They can utilize various kinds of resources and their population ecological similarity was heavier. It demonstrated that there was strong competition between two species for nature resource.In a multidimensional space, the niche overlap value of two populations was high in certain dimension and low on the contrary. This condition related with habitat asymmetry...