The Study Of Salt Accumulation Effect Of Meadow Wetland In Yinchuan Plain

With high ecological value, Wetlands are one of the important ecosystems on Earth. According to the research of wetlands in arid and semi-arid regions, the meadow is considered wetland types on over wet soil of land. The meadows in this study which belongs to lowland meadow, is mainly distributed in low-humidity areas like the riverfront, floodplain, valleys and depressions, its vegetation types have intrazonal characteristic, and not to show regional distribution.By using field investigation, laboratory analysis method, this paper studies the distribution characteristic of Yinchuan plain meadow wetland vegetation, the classification of soil salinization in meadow wetland, the status of salt accumulation, the main component of salt and the main factor that impacts of meadow vegetation distribution and growth characteristic in Yinchuan Plain. The research process and main conclusions are as follows:(1) In this study,57 experimental plots with 123 points were set. Through the traditional classification method, the plant communities in the study area are divided into 3 vegetation types,8 vegetation subtypes,27 formations. According to the soil surface salinity (0～20) cm, the soil in the study area is divided into 5 grades:Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, their corresponding salt content are≥10g/ kg,4～<10g/kg,2～<4g/kg,1～<2g/kg and<1g/kg.(2) Plant diversity index showed Ⅴ> Ⅲ> Ⅳ> Ⅱ> Ⅰ, which Pielou evenness index showed Ⅰ> Ⅲ> Ⅴ> Ⅳ> Ⅱ, it indicates that with the increase of soil salt content, plant diversity index is lower and community structure changes to be more simple.(3) The total salt content of meadow soil in study area in the vertical direction showed obvious surface aggregation phenomenon. In 0～30cm soil layer, with the increase of soil depth, soil salinity has a sharp decline. In the 30～70cm of soil, total salinity decreases more gentle. Each salt ions except HCO3-, CO32- showed obvious surface aggregation phenomenon, but in different soil grade, only Na+, K+, Cl- have consistent performance with soil salinity, they are both Ⅰ> Ⅱ> Ⅲ> Ⅳ> Ⅴ.(4) Meadow wetland plant also has some salt accumulation. In the plant, the salinity is mainly NaCl, NaHCO3. In soil the salinity is mainly NaCl, NaHCO3, Na2CO3.(5) Wetland meadow correlation analysis results of soil salinity factors indicate that soil salinity, pH and most of salt ions appears to be significant or very significant positive or negative correlation. There has a significant or very significant correlation between Na+, Cl- and most of the ions. All the main components analysis of salt ions showed that:in 0～30cm, Na+, Cl- are main salt ions in the study area, in 30～100cm, Na+, Ca2+, Cl- are mainly the salt ions of salt accumulation in the study area.(6) According to the RDA analysis of meadow community characteristics in study area and 9 soil environmental factors screened out by Variance Inflation Factor, plant community characteristics share more vespertine at I axis and VI axis respectively 31.5% and 67.9%, the cumulative amount of information community characteristics vespertine is 99.5%, Na+, Cl-, TS play a very good role for explanation at variation of plant community characteristics. Na+ has significantly negative correlated relationship with plant community biomass. Na+ content has negative correlation with biomass, coverage, the number of species and Cl" content is same as Na+ content, but the correlation is not significant.(7) Yinchuan Plain wetland meadow soil salinity is the spatial variation of increasing from south to north. Salinity size of different types meadow is salty vegetation> Typical meadow> wet meadow. Salinity size of different topography sites grass is the dry lake beach> floodplains> lake beach outside river levee> wet lake beach> sand beach in drains side. The depth of groundwater and water-salt cyclical process are the decisive factor in terms of salt distribution character.