Plant Growth Status In Relation To Community Structure In Typical Landscape Forests In The Urban Area Of Shanghai

There is a growing body of the landscape forests in the urban area of Shanghai city, since the greening activity was performed. However, these forests were undergoing a series of ecological issues, such as overloading of plant density, more closuring of community canopy, and lower level of species richness. Hence, it is important in both theory and practice to link forest types, community structure and tree growing status together to establish their relationship, in order to improve understanding how to optimize the community structure.In this study, the main landscape forests in urban area of shanghai city were investigated and classified by using Franco-Swiss school methods, and then 4 typical forest types (i.e. Magnolia grandiflora, Cinnamomum camphora, Ginkgo biloba and Metasequoia glyptostroboides dominated forests, respectively), were selected to establish relationships among community structure, plant leaf traits and environmental factors. In each of the 4 forest types, the plot gradient including 7 to 8 plots was formed according the similarity of the community structure and the species identity. Then, forest community structure, plants growth performance such as leaf traits, and environmental factors such as soil fertility, soil moisture and soil electrical conductivity were examined and related each other, aiming to find the limited environmental factors, which may contribute to the community structure. Finally, the economical and ecological community structure and species composition were proposed.The main results in this study were as follows:1) There were 4 landscape forest types and 25 community types in the urban area of Shanghai city, according the community classification (TWINSPAN screening of 215 plots).2) Among 4 forest types, the community structure was incomplete, the tree layer was dense (coverage>80%), and species richness was low (tree and shrub layers in particular).3) Soil bulk density and moisture, contents of soil organic carbon, nitrogen and phosphorous, soil electronic conductivity and pH, and air temperature and humidity were significantly affected by the plots gradient among 4 forest types (p<0.05), with the exception of soil bulk density in Magnolia grandiflora forests, and soil total nitrogen in Ginkgo biloba forests (p>0.05).4) The leaf traits including specific leaf area, contents of carbon, nitrogen and phosphorus were generally higher in the plots that were represented by a good performance of tree growth and community structure, than their counter-plots, suggesting plant leaf traits could indicate plant growth performance and community structure. Additionally, the leaf N:P ratio was generally high over all plots, indicating the phosphorus was the main growth-limiting factor in the landscape forests in Shanghai.5) Basing on the significant relationships among community structure, plant leaf traits and environmental factors, and referring by the local potential vegetation types, I recommended 5 evergreen broad-leaved forest types,5 deciduous broad-leaved forest types,5 evergreen and deciduous mixed broad-leaved forest types,3 deciduous coniferous forest types, and 2 evergreen and deciduous mixed coniferous forest types, as the reference forests to optimize the typical landscape forests in the urban area of Shanghai city.