The Research To Community Structure, Ecological Function And Adjustment Of Roadside Green Space In Pudong, Shanghai

Roadside green space is an indispensable part of the urban green space system . As a green corridor, it connects with various green space inside and outside the urban forming the urban green network .The roadside green space plays an important role in organizing urban traffic, improving ecological environment and beautifying urban landscape. The community structure about 9 roads and the ecological function about 6 roads in Pudong were investigated. To the outstanding problem, this paper explored adjustment approaches of community structure. On the basis of scientific analysis, this paper put forward suggestions on construction and adjustment of roadside green space in Pudong, Shanghai. The results are as follows.1. Community structure analysis of roadside green spaceAccording to China Vegetation Classification System, the roadside trees in Pudong are classified 2 subclass vegetation types including needle-leaved forest and broad-leaved forest, and 5 vegetation type groups including needle-leaved forest, needle broad-leaved forest, deciduous broad-leaved forest, evergreen deciduous broad-leaved forest and evergreen broad-leaved forest.The floristic elements are complex of roadside green space in Pudong. According to Wu Zhengyi's compartmentalization on the areal types of Chinese genera of seed plants, it is divided into 13 genetic areal types, except the temperate asia and central asia elements.Community types are various,but plant species are single, community structure is sample, species diversity is low, and plant arrangement is irrationality. Tree have 9 genera 11 families 12 species, shurb have 20 genera 28 families 30 species, and herb have 24 genera 36 families 36 species. Most of herbs are wildlife, and 7 species are cultivated.Having great stand density is the outstanding problem of roadside green space in Pudong. There are many morbid trees, and along with the greater of density, trees are worse growth. Anlysis stand density and tree factors shows density correlated negatively with DBH and crown width. Density and DBH of Populus euramevicana community have quadratic relationship, y=-1E-07x²-0.0002x+17.276 (R² =0.9476) ; density and crown width have quadratic relationship, y=1E-07x²-0.002x+16.673 (R²=0.8120) . Density and DBH of Cinnamomum camphora have power relationship, y=142.03x^-0.3468(R²=0.8816) ; density and crown width have power relationship, y=997.71x^-0.6055 (R²=0.9475) . Density and DBH of Metasequoia glyptostroboides have quadratic relationship, y=2E-07x²-0.0029x+17.187 (R²=0.7575) ; density and crown width have quadratic relationship, y=1E-07x²-0.0019x+8.4885 (R²=0.9088) . Along with the greater of density, height of the lowest branch of Cinnamomum camphora and Ligustrum lucidum are higher.Along with the greater of canopy density, light intensity decline ascends from 84.81% to 94.03% , and Shannon—Wiener index descends from 2.8229 to 2.7308, but Simpson index ascends, and Pielou index has no conspicuous change.2. Ecological function analysis of roadside green spaceThere are conspicuous differences of ecological function among 6 roads greening in Pudong. Yuandong's roads greening has good ecological function, and Longdong, Huandong, Huannan's common, and Luoshan and Yanggao's bad.The effection of weakening noises are as follows: trees+shrubs+herbs (12.8%) >trees+shrubs(10.4%)> trees+herbs(8.8%)> shrubs+herbs(7.4 %).The dust retention are as follows: trees+shrubs+herbs (33.3%) =trees+shrubs(33.3%)> trees+herbs(28.6%)> shrubs+herbs(0%). The effection of improving microclimate are as follows: trees+shrubs+herbs >trees+shrubs > trees+herbs .Different community type has different ecological function. Nerium indicum, Populus euramevicana, Bambusa glaucescens, Cinnamomum camphora community have better function of weakening noises, and Nerium indicum, Metasequoia glyptostroboides Cinnamomum camphora community have better ability on the dust retention. Populus canadensis and Salix babylonica community have better function to restrain bacteria.Canopy density has conspicuous effect to produce the ecological function of roadside green space. Along with the larger canopy density, weakening noises ascends from 8. 92%to 11.64%, dust retention ascends from 8.82% to 52. 63%, improving microclimate is more conspicuous , but restrain bacteria descends from 39.7% to 13.0%.The greenbelt width from 15m to 30m, weakening noises ascends from 9.86% to 11.03%, dust retention ascends from 16.67% to 30.77%, restrain bacteria descends from 50. 54% to 19. 53%. The mature community has good ecological functions.3. Adjustment approach explored of roadside green spaceAccording to equation of DBH and crown transmission area or crown surface area, compiled Populus euramevicana and Cinnamomum camphora's density control tables. This article investigated and analysed Populus euramevicana, and Cinnamomum camphora communities structure which have long years and integrated forest form and reasonable community structure, and on this basis analysed and discussed characters of mold forest of Populus euramevicana and Cinnamomum camphora in order to provide quantify basis for establishing management program for urban green space and computing thinning intensity. This article make adjustment experiment to Populus euramevicana+Cinnamomum camphora community, and the forest density is 1200 trees/hm² after thinning which lowered 42.8%, and have 13 species which increased 44.4%, and cover plant rate by 38% which is three times larger than before thinning. After two years, plants grow well, and the significant tests for tree factors before and after thinning indicated that all factors were significantly different (P<0.01) . Therefor , when the community develops to a certain stage which has large initial seeding density, thinning is a effective approach to transformation of forest form.The community which has gap is increasing environmental heterogeneity.The results showed that herbs in the gap center were more diversity than that in the gap edge and non-gap, and tree seedlings in the gap center higher than that in the gap edge and non-gap because of the environmental changed. For example Exterior Loop Line, the preponderant tree seedlings in the gap center were above 20cm height and the percentage was 37.5%,the preponderant tree seedlings in the gap edge were between 6-10cm height and the percentage was 53. 1%, and the preponderant tree seedlings in the non-gap were between 0-5cm height and the percentage was 66.7%.