Plant Diversity And Soil Property Changes In The Restored Land/water Ecotones Of Northern Gonghu Bay

The aim of the present study was to determine the variation in vegetation distribution patterns,diversity indices,and soil characteristics under water level elevations in land and water ecotones,in the northern part of Gonghu Bay in 2015----2016.We adopt the statistical methods of species diversity calculation and exploratory factors statistics in quantitative ecology,explore the pattern of the variation in vegetation diversity along with water level elevation and correlation between soil physical and chemical properties which have provided evidence for protecting the vegetation diversity in Gonghu ecological demonstration area and sustainable development of ecology,the preliminary research results are as follows:(1)We give priority to these division indictors: the time of hydrological effect,water level elevation,soil mechanical composition,vegetation biomass,diversity indices.According to regression equation and principal components,we use hydrological time division,water level elevation,diversity factors as the index for guidance.Given the recent four years' monitoring water level change trend,we divide land and water ecotones in ecological restoration area into three gradient belts based on water level elevation and the types of vegetation: perennial flooded area---G1(2.8—3.3 m;from January to May is basically under 3.3m)(Wusong water lever is the same)Seasonal flooded area G2(3.3—4.3 m;from June to October maintain the highest water level),small amount of flooded area G3(>4.3 m;from November to December Gradually fall back below 3.3m).(2)The lake-land ecotone in GongHu bay ecological restoration area has abundant species composition.The water lever elevation has 165 species of plants,Belonging to 65 families and 142 genera,and most of those are perennial plants that are seriously affected by human.With the water level elevation rising,the Plant species number,evenness,dominance,coverage and diversity show gradually increasing trends which is expressed G1<G2<G3,the vegetation condition is good.(3)There are significant differences in the distribution of soil physical characteristics at different water land ecotone.The content of silt and clay in soil bulk density and mechanical composition increased with the elevation of water level and the content of OM increased in the form of "V";TN tended to increase gradually;The content of available potassium(EP)had no obvious fluctuation,approximately 13.50 mg/kg;The content of available phosphorus(AP)decreased firstly and then remained unchanged;TN was significantly positively correlated with OM(R2=0.533);OM was negatively correlated with EP(R2=-0.144).(4)Positive correlation was found between the 4 diversity indices,and TN was positively correlated with richness,diversity and dominance;AP was positively correlated with the 4 diversity indices,and the pH value was negatively correlated with the diversity index of the 4 species.The regression analysis showed that TN and OM were the key factors affecting the diversity of plant communities.