| The wetland resource is not only a special regional rare landscape, but also very important for maintaining ecological balance in arid and semi-arid areas. Wetland ecosystem has a function of stopping and controlling the periphery ecosystem, such as grassland and desert ecosystem, away from deteriorating. So studying the wetland vegetable characters in semi-arid region is much meaningful in ecology and realism.Taking Siertan wetland in Haba Lake desert-wetland natural protection area in Yanchi County, NFPE as an example, this dissertation studied the characteristics of wetland vegetation from 3 aspects: main vegetable styles and distribution characteristics, community species diversity, and community structure. According to different directions and different biotope styles, the sample land had been distributed using quadrat sampling method and sample line method. The survey had been lasting from June to September in 2007. The data was analyzed by the means of TWINSPAN and indices analyse of species and community by using community classification software WinTWINS, community ordination software CANNCO, biodiversity analysis software Biodiversity Pro and other ecological statistics software. On this base, the present status and characteristics of wetland vegetation community and plant species in Siertan were studied systematically. The main research findings were as follows:(1) Considering the realistic status, the vegetation in study area was classified into 3 types and 20 associations by the quantity classification method TWINSPAN. The three vegetation types were grassland vegetation, meadow vegetation and halophytic marsh vegetation.(2) It was showed in studying of communityα- diversity andβ-diversity of different biotope strips that otherα-diversity index, such as species richness degree index and plant diversity index, was the bigger in ecotone than other strips except evenness degree index which was bigger in drought strip. Analysis ofβ-diversity showed that the comparability between ecotone and drought strip was bigger than it between ecotone and wet strip. There were many differences on community species diversity between sample lines. Either richness degree index, specie diversity index or evenness degree index were higher in sample line of east, north and northwest than other directions. But they are much lower in west, southwest and south line. Reasons for it were something with artificial activity affected and different landform raising.(3) Studying vegetable quantity characteristic in different biotope types in research area showed that cover degree, specie amount, community height, density and biomass all changed a lot in three strips. Ecotone had the highest index on cover degree, specie amount and community height, while drought strip had lower index than it and wet strip had the lowest. For that different vegetation floor in community had different approaches of taking use of water resource, drought strip had higher density than ecotone, and wet strip had the lowest one. The biomass index changed in three strips just like this: wet strip>ecotone>drought strip, which was related with moisture content. There were differences of plant quantity character in sample lines of different direction. The west line had the biggest cover degree while the north line had the smallest. Taken the specie number in order was that: east > north > south > southwest t> northwest > west. The south line had the highest community height index while the other lines were in the same level. The plant density was bigger in north, west and east line, while smaller in south, southwest and northwest line. The north line had the highest community biomass index in sample lines, the southwest line was in the next place and the north line had the lowest one.(4) The calculation results of community structure index showed that the four community structure index had taken on the same orderliness in three strips, which is that ecotone had the highest richness degree, community zoology dominance degree and species'diversity index, while drought strip was in the next place, and the wet strip was the lowest. The comuunity evenness degree index of wet strip was the highest, but in ecotone it was the lowest. In different sample lines there was more difference on community structure characteristics. The east line had the biggest community richness degree, but the west line had the smallest one. Take the specie diversity index of different directions in order was that: east>northwest>north>southwest>west>south. Community zoology dominance degree had the same trend with specie diversity index between different sample lines. The west line had the biggest community evenness degree, while the south line had the smallest.
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