Carbon,Nitrogen And Phosphorus Ecological Stoichiometry Of Vegetation Community Under The Gradients Of Soil Water-salt In Chongming Wetlands

Chongming is a typical estuary alluvial island, seawater is upstream to islands, result that the soil salinity and moisture are different. Whether the vegetation that are widely distributed in Chongming is different in different habitats; or affected by water-salt. This research is to solve these problems, to study on the vegetation community ecological Stoichiometryunder the gradient of water-salt. We assume that vegetation and soil ecological stoichiometry will change under the gradient of water-salt. The object is the different communities and soil in Chongming islands. Using the ecological stoichiometry method to analysis the wetland vegetation and soil C, N, P content and stoichiometric characteristics, and and to explore the nutrient limiting factors of vegetation and the affect on vegetation ecological stoichiometry by water-salt.focuses on the relationship between vegetation and soil. The main research results are as follows:Ecological stoichiometry of Vegetation:C, N concentrationand N/P is generally lower thanthe nationaland global levels; while P concentration, C/N, C/P ratio were higher than the national and global level.This suggests that vegetation carbon storage capacityin the area is lower, N concentration of the plant are lower and P concentration is higher; N/P is less than the critical threshold of14nutrient restriction, and the research area of soil C, N scarcity, P concentration is rich features, the vegetation growth may be mainly restricted by N. Meanwhile C, N concentration and C/P, N/P of Phragmites australis were higher than the other two vegetation index.Community characteristics of P. australis increased with the increase of water-salt, Spartina alterniflora is contrary, Scirpus mariqueter is best under moderate soil; this can indicate that S. alterniflora is more competitive in the higher water-salt environment; while the P. australisand S. mariqueter were growing better in lower water-salt environment. Overall, the C concentration decreased first and then increasedwith the increasing water-salt, indicating that wetland vegetation C concentration affected by water-salt, but reaches a certain amount, the vegetation will have the corresponding adaptability to thewater-salt. The N concentration first increased then decreased, while the concentration of P will increase with the increasing of water-salt, which indicating that the water-salt may affect plant nutrient absorption and accumulation. C/N, N/P, C/P were increased with the water-salt increaseing.Three different soil factors have a significant difference,the soil pH, moisture content and electrical conductivity of S.alterniflorawere higher than that P. australis and S. mariqueter soil. Overall, wetland soil C, N, P concentration and C/P, N/P will increase with the increaseing of water-salt; And C/N will increase first after reduction with the increaseing of water-salt, soil C,N concentrations are lower than the national and global level, and the P concentrations are higher.Using the trend of correspondence analysis (DCA) and redundancy analysis (RDA) method to analysis the correlation between these ecological stoichiometry of three vegetation communities and soil factors, the results show that the soil P concentration and electric conductivity are the main factor of plant differentiation, soil pH and communities factor of S.alterniflora are negative correlation, which indicating that S.alterniflorare more competitive in higher water-salt. Water-salt factor have positive correlation with plant height, coverage, density; and negative correlation with biomass.Based on features, ecological stoichiometry and soil of three vegetation, found that P. australis is more suitable in lower water-salt, S.alternifloraare more competitive in heavy water-salt soil, S. mariquetergrows well in moderate water-salt soil.