Study On Plant Community Structure And Its Effects On Soil Chemical Properties In 1hm~2 Plot Of Chongming Island In Shanghai

Soil is the material foundation for plant's growth and development,and vegetation plays a vital role in chemical properties and biological processes of soil.Therefore,they interact and promote mutually.Soil is an important part of cities'ecosystem,it plays a vital role in ecological environment,and studying soil and urban vegetation system is of great significance to the sustainable development of cities.This paper takes 1hm~2 sample plot of Chongming Island in Shanghai as the research object to analyzes the community structure of sample plots in Chongming Island from several aspects such as species composition,community type and species diversity;determine the soil chemical traits of each community,understand the soil nutrients condition of Chongming Island plantation,analyze the correlation between soil chemical factors and species diversity in different communities and the correlation of soil physico-chemical factors in different community soil types which helps the stability of urban ecosystems.The main conclusions are as follows:(1)There are 65 species of vascular plants in the plot which belong to 33 families and 62genus.Plant species and quantity increased significantly compared with 2011 and 2015,especially the quantity of renewed seedlings increased rapidly in community,and the distribution concentrating led to a large community density and complex community structure,inter-species infiltration and mixed distribution pattern tend to be obvious.(2)The species richness and diversity index of the herb layer were apparently higher than that of the tree layer,and the index among the communities have few difference,which indicate that the herb layer in community was stable;the richness and species diversity index of the paper mulberry community in the tree layer is the lowest among all community types,which indicate that the paper mulberry community is unevenly distributed and the community structure is unstable;the species diversity index of the co dominant type community is not as good as that of the single-type,which indicates that the co dominant type community in the Chongming plot is still in development phase and not mature and stable.(3)The soil of Chongming Island plantation is alkaline,the pH value is between 8.01 and 8.36,which is within the range suits for plant growth;the soil organic matter content is mainly moderate;the total soil N content is between 0.63 and 2.09 g/kg,the effective N amount is between 76~147mg/kg,and the whole community is rich;the total soil P is 0.52~0.88g/kg,which is in the lack and low degree,the effective P content is 2.09~15.23mg/kg,and among them,Koelreuteria bipinnata community is in a lack or extremely lacking degree;the total K content of soil is 21.75~24.5g/kg,the effective K quantity is between 155~283mg/kg,and both of them are rich;effective Fe content is 82~153mg/kg,effective Mn content10.31~15.95mg/kg,which are high content,while effective Mo content is between0.07~0.13mg/kg,which are low content,some plants have symptoms of short stature and slow growth,and some leaves appear yellow spots in different sizes.(4)There are some connections between species diversity and soil chemical traits,Shannon-Wiener index was remarkable positively correlated with soil pH(p<0.05),and soil total K content was remarkable negatively correlated with Simpson index and Pielou index(p<0.05).The higher the diversity index,the higher the soil pH value,the weaker in acidity or stronger alkaline of soil;the correlation among soil organic matter,total N,total P and diversity index is not significant relevant or relevant;the greater the diversity index,the smaller the K content in soil.(5)There is a remarkable positive correlation between soil water holding capacity among the field and total soil porosity in Firmiana platanifolia community(p<0.05);In Metasequoia glyptostroboides community,soil bulk density was remarkably positively correlated with chemical factor pH(p<0.05),there is a remarkable positive correlation between total soil porosity and soil organic matter(p<0.05),and the physico-chemical factors in other communities did not reach significant levels.