Characterization And Mechanism Of Degradation Of Wetland Plant Communities On Floodplain In Typical Steppe Region Of Inner Mongolia Plateau

River floodplain meadow in Inner Mongolia plateau typical steppe is the area with the most fully biodiversity performance and the highest biological productivity, but the vast majority of meadow is in a degraded condition due to the excessive grazing use. We study area topography, community composition, soil physical properties, soil micromorphological characteristics during June to September in2010-2011and compared with the typical grasslands and Investigate the characterization and mechanisms of degradation wetland. Conclusions are as follows:(1) Grazing maked the dominant species in wetland changed, the original wetland plants gradually changed drought biochemical, plants was showing significant small-scale phenomenon, while the biomass on ground and below-ground were significantly reduced.(2) Grazing trampling caused soil bulk density and soil compaction increase, soil water content of degradation wetland in grazing area less than the enclosed conservation wetlands. In the low flood plain, soil moisture increased with increasing soil depth, the root amount tends to be deep. But in the high floodplain wetlands, soil moisture is close to the typical steppe, the root distribution does not appear deep trend. Grazing makes soil microbial biomass increased in the low floodplain wetland while in the transition zone and high floodplain wetlands, grazing makes the soil microbial biomass carbon, and nitrogen content decreased significantly. Corresponding to the wetland vegetation, in enclosed wetland the trends of soil total nitrogen, total phosphorus in the soil vertically were consistent, soil particles of the grazing area was crushing, roots was less than the amount enclosed areas, the measured porosity was less than the enclosed area, and in the surface the porosity was smallest. In enclosed area the soil color is dark compared with grazing area, and soil organic matter content is higher in enclosed area.(3) Soil moisture is the main factor affecting wetland plant community biomass. Grazing makes the soil water content reduced, thereby it also reduced the community productivity. Grazing significantly reduced soil moisture and nutrient content, making the biomass on ground and below-ground reduce. Although grazing reduced the aboveground and belowground biomass, it didn’t change the vertical distribution law of soil moisture, soil bulk density, soil total nitrogen and total phosphorus.