Characteristics And Ecological Function Of Egetation Of Wetland In The Mu Us Sandy Land

Wetland ecosystem is located at the ecotones between terrestrial ecosystem and aquatic ecosystem. Wetland area accounts for5.4percent of global land area, but its importance is no less than the forest ecosystem and marine ecosystem. Especially for the water depletion semi-arid region sandy land in China, it is known as "vegetation island" in the sandy land. It is not only the main space of human survival in the sand areas, and also very important for the maintenance of ecological balance in the sand areas. Mu Us sandy land is a major sandy in semi-arid inland region of China, and is a very special and sensitive ecotone. So, this paper took the wetland of Mu Us sandy land in Inner Mongolia as the research object, analyzed the floristic composition of wetland, distribution of the plant community and its influencing factors, vegetation dynamics change and its impact on plant diversity, aboveground biomass and soil organic carbon storage, and also discussed the characteristics and ecological functions of vegetation of wetland in Mu Us sandy land from the different scales. The main results are summarized as follows:1. The area of wetland in the Mu Us sandy land is about4486.54km2, which is18.75%of the Mu Us sandy land. The wetland types are represented by inter-dune lowlands, lake lowlands and beaches. The distribution series of wetland types with increasing altitude was flood plain→lake shore lowlands→inter-dune lowlands and beaches.2. The wetland vegetation in the Mu Us sandy land not only has the intrazonal characteristics, also has the obvious brand of the zonal vegetation. The world distribution family is the main family in the plant family distribution types, but the temperate distribution genera and species are the main genera and species in the plant genera and species distribution types. The plant species distribution type of wetland in the Mu Us sandy land is more similar to the typical steppe in the Ordos Plateau (Dongsheng ridge, and the Junger loess hills), the effects of East Asia elements are stronger than the Steppe elements. And comparied with wetland vegetation of Heilongjiang River valley in humid and semi-humid region, the main plant community type of wetland in the Mu Us sandy land is meadow, but the main plant community type of wetland in the Heilongjiang River valley is swamp.3. The plant communities of lake shore lowland and inter-dune lowland in the Mu Us sandy land has a zonal distribution featuers. However, there are differences between the influencing environmental factors of the zonal distribution of plant communities of lake shore lowland and inter-dune lowland. The distribution of plant community on the lake shore lowland is affected by water and salinity gradient, and that on the inter-dune lowland is affected by water and soil mechanical composition (size fraction is0.05～μm).4. The shrinking, salinization and breaking of wetland is more and more serious in the Mu Us sandy land. The wetland area has been reduced by618.53km2, the saline land area has been increased by163.48km2and the landscape fragmentation index has been increased by0.000023from1986to2007. This is resulted from a combination of climatic factors and human factors such as temperature rise, evaporation enhancement, the Dune stabilization practice, forestry planting and agricultural land reclamation.5. As a valuable resource in the Mu Us sandy land, wetland plays an irreplaceable role in the maintenance of biodiversity, production of dry matter and the carbon cycle. There are323wild vascular plants in the wetland, accounting for72.1% of that in the Mu Us sandy land, and wetland plant species diverssity is significantly higher than the sandy land and ridge of the same region. The herb layer production of the wetland vegetation is310072.43t, accounting for68.98%of that in the Mu Us sandy land, soil organic carbon storage (0-30cm) in wetland is5735.93t, accounting for46.29%of that in the Mu Us sandy land. The species richness,aboveground-biomass and soil organic carbon storage (0-30cm) of the osier bed was significantly higher than other plant community in the Mu Us sandy land (P<0.05).6. In spite of the wetland in the Mu Us sandy land has an important ecological function, it also faces ecological problems as shrinking, salinization, breaking and functional degradation. Therefore, the protection and sustainable utilization of wetland resources in the Mu Us sandy land may be implemented by the follow countermeasures:(1) Raising awareness of wetland protection;(2) Guaranteeing wetland ecological water;(3) Strengthening scientific support of the wetland conservation.