Stable Mechanism Research Of Caragana Tibetica And Stipa Brevifiora Compound Communitiy

As the typical plants of steppe desert and desert steppe, Caragana tibetica and Stipa breviflora formed distinctive appearance and stable zonal compound community in the grasslands-desert ecotone of ordos plateau. In arid areas,water is the most important ecological factors. We conducted seed germination experiment, moisture competition and the initial water absorption layer experiment, root distribution characteristics and the soil nutrient status between Caragana tibetica and Stipa breviflora. We drawed the following results:(1)The ability of seed germination of Caragana tibetica was stronger than that of Stipa breviflora. The similar seeds germination conditions showed that two kinds of seeds could finish normal germination,which may be one of the conditions maintaining long-term stability as the typical vegetation between grassland and desert.(2)There exists a commensalism relationship between Caragana tibetica and Stipa breviflora.Stipa breviflora had a stronger competitive advantages of using shallow water than Caragana tibetica in ecotone and Caragana tibetica had a better drought tolerance;(3)Root distribution characteristics showed that there were ecological niche separation and overlap between Caragana tibetica and Stipa breviflora. On the one hand Stipa breviflora could make formation of competitive advantage of shallow water, on the other hand double roots distribution characteristics of Caragana tibetica made up a competitive disadvantage of water use, which avoided the direct competition on water with Stipa breviflora. The root distribution characteristics of Caragana tibetica and Stipa breviflora is one of the conditions of forming compound community and maintaining stability.(4)In compound community, Caragana tibetica vegetation dunes possessed the ability of nutrients enrichment, it increased the spatial heterogeneity of compound community, which could redistribute water and fertilizer and contain more species coexistence. The process made compound community be stable. In compound community, ecological niche separation between Caragana tibetica and Stipa breviflora and a series of ecological adaptation mechanisms of Caragana tibetica are the reason of stable mechanism of compound community.