The Spatial Pattern Of Desert Vegetation And Its Forming Mechanism In Alashan Desert

In this paper, westudiedthedesertvegetation in Alashan,combined remote sensing and geographical information technique with field investigation, we analysised the desert vegetation and their spatial patterns in Alashan desert, and discussed the formation mechanism of the desert vegetation pattern from the perspective of climate, soil and micro habitat. Research suggests that main conclusions are as follows:1.The desert vegetation types of Alashan included8vegetation types and32representative plant formations.8vegetation types were degraded-leaf and semi-arbor desert; laurifruticeta desert; laurifruticeta and degraded-leaf desert; degraded-leaf shrubs desert; degraded-leaf shrubs desert; chylophyllous shrubs desert; drought born leaf shurbs desert; chylophyllous semi-subshrubs desert and Xeromorphic-leaf and semi-subshrub desert. And the largest area is succulent shrubs desert, accounting for43.35%of the total area of desert vegetation; the largest area of plant formation is Form. Reaumuria soongorica accounting for29.56%of the total area.2. Climate is the reason that affects the the large-scale formation of vegetation pattern of the Alashan desert. According to climatic factors, Alashan desert region can be divided into three classes:mid temperate steppe desert climate zone, mid temperate desert climate zone and warm temperate hyper-arid desert zone. From the hyper-arid deserts to steppe deserts, plant community diversity, plaque richness and mean patch area are decreased. Plant distribution is more smaller, and also species richness is, when the the climate is more drought.3. In the same climate region, soil type and plant community as not significantly t. But soil mechanical composition is an important factor1). The mechanical composition of the soil surface (0-30cm) a significant impact on the plant formations. Clay content of different plant formations in descending order as follows:Form. Caragana tibetica> Form. Kalidium ssinicum> Form. Sympegma regelii> Form. Salsola passerina>Form. Reaumuria soongorica>Form. Ammopiptanthus mongolicus>rm. Ephedra przewalskii>FormArtemisia blepharolepis>Form.Haloxylon ammondendron>Form. Nitraria tangutorum>Form. Nitraria sphaerocarpa>Form. Potaninia mongolica>Form. Brachanthemum pulvinatum>Form. Oxytropis aciphylla>Form. Convolvulus tragacanthoides>Form.Gymnocarpos przewalskii。2). The content of clay in the subsoil (30-100cm) the length of the roots of plants have a significant impact. In general, the more clay content in the underlying soil, the shorter plant root length.3). The diversity of soil matrix is the important reason of community diversity in east Alashan steppe desert zone. In other words, soil heterogeneity is the main reason of community diversity and heterogeneity. 4. The microhabitat changes plant community distribution in extremely-arid desert. Plant communities are concentrated in a relatively higher rainfall area of gullies, dry riverbed or water runoff line,and Other vast regions are no vegetation or bare land of rare vegetion.