Study And Assessment Of Vegetation Communities Structure Of The Green Space In Shanghai New Jiangwan

Plant community is the basic unit of urban landscapes. It is the basis of urban system with its ecological functions, and is also the premise of improving the richness of the green space, as an important sign of landscape development of the city. Building up a scientific and reasonable plant community structure makes the green spaces more stable, efficient, and healthy occupied the most important position. The beauty of landscape is reflected by plant community structure, and many other aspects, such as life form of dominant species, species diversity, density class, seasonal changes, community level and so on。Diverse species like Shrubs and grass in plant community and the fine Stratified structure of the vertical configuration, also the roadside green space are the best illustration of species diversity and mutual penetrated configuration of vertical structure and horizontal structure. In order to give people aesthetic pleasure by increasing the amount of green space and enjoying the changeable color view, they offered people the aesthetic pleasure and the great enjoyment of the colorful view. At the same time, they've played the wonderful ecological effects. Therefore, with the in-depth study of urban vegetation and the rapid development of modern garden, it is imperative for us to use the lowest cost to maximize the ecological benefits by invoking the self-regulating function of plant community.In the study, we choose New Jiangwan green space as studying object. Investigating areas distributing are distributed from Ecological conservation area, the central isolated communities of Songhu Road to Ecological Corridor, we look into Species composition, life form, geography fauna, community type, source species and biodiversity etc. Use QMSW-Quantum Meter to get illumination value; Adopting AHP method to construct Landscape Evaluation system; Draw plant distribution map of several typical plots, the conclusions are as follows:1).During this investigation, there are 242 species of vascular plants in all, which belong to 94 family and 205 genera. Among these plants, there are 2 species of Ferns, which belong to 2 family and 2 genera; there are 6 species of Gymnosperm, which belong to 5 family and 6 genera; there are 226 species of Angiosperm, which belong to 85 family and 188 genera. Specie amount of arbor is 55,belonging to 33 family and 49 genera; Specie amount of bush is 52,belonging to 27 family and 40 genera; Specie amount of liana is 12,belonging to 9 family and 11 genera; Specie amount of herbal is 122,belonging to 46 family and 106 genera; from the view of species composition, Composita,Gramineae,Leguminosae and Rosaceae appear with higher frequency and can be considered as the dominant species of New Jiangwan green space; From the view of genera, seed plants mainly distribute in north temperate and pan-tropical area which accounted for 36.5% of the whole genus. And this meets is in well accord with the characteristics of shanghai climate.2). New Jiangwan City is rich in plant community type, with evergreen forest and evergreen broad-leaved forest as two mainly types, whose occurrence frequency were 47.9% and 14.6%.although the statistics of evergreen forest and evergreen broad-leaved forest is higher,its type in shortage.Kinds of herbal is the richest, which mainly is Perennial herb. Secondly, the arbor mainly is leaved forest specie, which is about double of evergreen forest. Moreover these species mostly are cultivars or alien species, especially in roadside green space. Cinnamomum camphora (L.) Presl.and Ligustrum lucidum are widely distributed around Jiangsu and Zhejiang so it still has strong zonal characteristics. Shrubs are dominated by evergreen species. This shows that deciduous trees and evergreen shrubs occupy an important position in this area. Not only form a rich community level, but also be better in line with seasonal landscapes.3).From the view of appearance frequency of species, Cinnamomum camphora (L.) Presl., Ligustrum lucidum, Elaeocarpus sylvestris(Lour.), Celtis sinesis Pers., Fatsia japonica (Thunb) Decne et Planch and Euonymus fortunei(Turcz.)are the Common species. Cinnamomum camphora (L.) and Ginkgo biloba are the dorminant species in the whole New Jiangwan green space. However, Native species, like Castanopsis sclerophylla (Lindl.) and Cyclobalanopsis glauca are rare even none. This is because alien species were introduced frequently these years in into Shanghai. The plant community of Ecological Corridor mostly consisted of pure forest while roadside green spaces adopting artificial garden layout design in order to achieve some beautiful landscape effect.4). Species richness index(s), Shannon-Wiener index and Simpson index of plant community in New Jiangwan area show a common trend:herbal>bush> arbor; Among these indexes, ecological corridor and green eco source own the highest richness index,and their species uniformity as well. This shows that roadside green spaces focused on view of community much more while other two investigated area are good at Self-sustaining with high biodiversity and own more stable,healthy ecosystem.5). It is a significant positive correlation between Canopy density and the light fall (P<0.01), a significant negative correlation between Canopy density and species richness index, and a significant Negative correlation between the light fall and species richness index. It shows that with the increasing of canopy density, the fall between outside forest and inside forest become lager, at the same time, species richness of herbal tends to decrease. With the increase of canopy density, understory herbaceous species increased firstly and then decreased; In the middle canopy density conditions, it is the herbaceous species that is most abundant; With light intensity, understory herb species richness first increased and then decreased.6). In this paper, AHP and Principal Component Analysis methods were used extensively to establish an ecology well coordinated with landscape evaluation index system and weight was caculated. The result shows:there is none plant community belonging to the first grade; nine communities belong to the second grade which account for 20.93%.New Jiangwan green space has been built up for not too long term, just because of this, communities don't have enough time to arrive a stable growth state.as a result, maintaining their level of steady development is going on, so the overall assessment of value is not too high. More integrated communities with high levels of native trees, foliage species, flower species also account for a large proportion, not only enriched the plant community type, and greatly increased the visual effects community in New Jiangwan City.