关键词: 鄂尔多斯高原, 灌木类群, DCA排序, TWINSPAN分类

Abstract: The Ordos Plateau is relatively an independent natural unit in the semiarid area of China. Viewed from geology and geomorphology, hydrology, pedology, botany, human and society etc., it is also a multiplied-levels, typical and complicated ecotone. Due to its specific nature condition, history and ecological background, there are abundant shrub community. So it is called as a "Natural Shrub Kingdom". It is a center of shrub biodiversity distribution and origin of temperate steppe in China. The middle western part of the plateau is a transition zone from desertified steppe to steppefied desert. The shrub community changes obviously from east to west with the decreasing precipitation. The paper, based on quadrat investigation and meterological observatory data, has established a set of data about plant community quadrat as well as environmental background through appling EIS interpolation method and relative regression equation, and has classified, oridinated the main shrub community and explained their relation with environment by using oridination and TWINSPAN classification methods. As results, the distributing pattern of main shrub communities with precipitation gradient variation in the middle western Ordos Plateau was given out in DCA ordination; some special community such as Helianthemum solgaricum one was ordinated correctly. They all practically responsed the different community habitat, especially the ground mass variation. The result of TWINSPAN classification has also reflected the characteristics of community habitat, especially the differences of water condition. The comprehensive analysing results show that water is the key factor controlling the distributing pattern of shrub communities; other factors such as temperature, days of sand storm, hours of sunshine, annual average wind velocity have not obvious influencing effects, which has something to do with that the Ordos Plateau distributes in limiting latitudinal stride and the main shrub species adapt to high temperature and rich sand storm for a long time. Moreover, soil mass property also play an important role in the distribution of shrub communities and its functional mechanism is look forwards to be further studied.

Key words: Ordos Plateau, Shrub community, DCA ordination, TWINSPAN classification