Abstract:

In order to find the species diversity characteristics of vegetation community at desert-oasis ecotone and the mechanism of maintenance of species diversity and community stability among different life forms, the author researched the species composition, community structure and plant species diversity of the 8 vegetation communities at desert-oasis ecotone in Minqin desert. The results showed that: (1) the shrub layer was dominant in species composition and quantity, the proportion was more than 56.86% in the vegetation communities except Reaumuria songarica community. The quantity of perennial herbs was relatively stable, but has a relatively low proportion in the whole community(only0.30% to 3.14% ) except in Artemisiaarenaria community (6.65%).(2) The important value of which in Nitraria was the highest for 84.41%, while in Oxytropis aciphylla community was the lowest for 20.70%, the others are changing from 56.78% to 68.07%. (3) All of the species diversity indices were low, from big to small was: Oxytropis aciphylla community＞Potaninia mongolica community＞Reaumuria songarica community＞Artemisiaarenaria community＞Calligonum mongolicum community＞Salsola passerina community＞Ephedra przewalskii community＞Nitraria community. All these communities have low species richness and inter-specific encounter rate, high ecological dominance, and uneven distribution of species, which explained the major species were dwarf shrub and semi-shrub, and perennial herbs had a relatively low proportion. Dominant populations in the desert shrub community have very prominent status and role were, which had more important role than the other species in community structure, the process of ecosystem function and community succession direction. The desert shrub community was unstable for lacking of the species redundancy.