A Study On Urban Tree Canopy And Urban Forest Structure Of Schools And Hospitals In Beijing Urban Area

At present,the rapid urbanization process makes ecological land be squeezed continuously,various environmental problems occur frequently.Urban forest has many advantages,such as high biomass,strong stability,long life cycle and good ecological benefit.It has become an effective way to solve urban environmental problems.Therefore,the research on urban forest has important practical significance to the construction of urban forest.This paper is based on the Arc GIS platform,using the refined World-View-2 remote sensing image of 2013 in 7-9 months,the canopy cover grid and vector map of the six ring rd of Beijing city and the field sample survey data,Two perspectives,from the canopy coverage(real crown coverage and potential canopy coverage)and urban forest structure(tree species composition and spatial structure),are used to analyze quantitatively and evaluate the status of urban forest in schools and hospitals in Beijing.The main conclusions are as follows:(1)Urban tree canopyThe total UTC of the schools and hospitals within six ring rds of Beijing,respectively,are27.62% and 18.59%,and the potential UTC,respectively,is are 3.61% and 1.55%.and70.93% of schools and 62.50% hospitals are in medium coverage and low coverage.The number of campus numbers in sever low coverage and sever high coverage are lower,only1.93% and 8.74% respectively,and hospitals are higher.11.72% and 14.84% respectively.The UTC of different ring road in the school shows that 4-5 ring rd(30.42%)>5-6 ring rd(29.46%)>3-4 ring rd(25.52%)>2-3 ring rd(23.62%)>2 ring rd(18.67%),and the potential UTC shows that 5-6 ring rd(5.57%)>3-4 ring rd rd(4.03%)>2-3 ring rd(1.91%)>4-5 ring rd(1.28%)> 2 ring rd(0.85%).The UTC of different administrative regions shows that Haidian District(30.04%)> Chaoyang District(25.03%)> Shijingshan District(23.18%)> Fengtai District(21.65%)> Xicheng District(21.21%)> Dongcheng District(12.92%).The potential UTC shows Fengtai District(4.16%)> Chaoyang District(2.39%)>Shijingshan District(1.66%)> Haidian District(1.59%)> Xicheng District(0.90%)> Dongcheng District(0.01%).The UTC of different ring road in the hospital is as follows: 5-6ring rd(19.15%)>3-4ring rd(13.03%)>2-3ring rd(11.64%)>4-5ring rd(11.18%)>2 ring rd(8.16%),and the potential UTC is :5-6 ring rd(0.03%)>4-5 ring rd(0.01%),other loops were 0.The UTC of different administrative regions is as follows: Shijingshan District(24.49%)> Haidian District(21.67%)> Chaoyang District(20.11%)> Fengtai District(19.43%)> Xicheng District(13.52%)> Dongcheng District(10.55%).The potential UTC in each administrative area is almost 0.The UTC in the affiliated green space of Beijing city shows: residential area(29.67%)>School(27.62%)> unit(26.88%)> hospital(18.59%),and the potential UTC shows: School(3.61%)> hospital(1.55%)> unit(0.64%)> residential area(0.22%).The largest UTC of each type of land can reached is school(31.23%)> residential area(29.89%)> unit(27.52%)>hospital(20.14%),all still below the total UTC of 39.53% in Beijing city.(2)Urban forest community structure characteristicsThe highest frequency of tree species application in schools and hospitals is respectively are Sabina chinensis(27.21%)and Magnolia liliflora(31.82%).The highest frequency of shrub tree species both in school and hospital are Buxus megistophylla Lévl(22.79%,31.85%).The tree species with higher application frequency in every ring rd road are Sophora japonica,Sabina chinensis,Magnolia denudata and Populus tomentosa,and shrub species including Buxus megistophylla Lévl,Buxus sinica,Berberis thunbergii,Syring rda oblata,Amygdalus triloba and Lonicera maackii.Among the 20 top ranked tree species in schools,hospitals,residential areas and units,the common species are: Pinus bungeana,Sophora japonica,Platanus hispanica,Cedrus deodara,Ginkgo biloba and Pinus tabuliformis.The special tree species in the school are Salix matsudana,Populus ×canadensis Moench and Paulownia tomentosa.The special tree species in the residential area are Ailanthus altissima,Salix babylonica and Toona sinensis.The special tree species in the hospital are Sabina chinensis(L.)Ant.’Kaizuca’,Metasequoia glyptostroboides,Armeniaca vulgaris Lam.and Lagerstroemia indica.The special tree species in the unit are Juniperus formosana,Eucommia ulmoides,Ulmus pumila and Juglans regia.Richness and diversity index shows: unit > residential area > School > hospital.The species richness indexes of the school in different loops are as follows: 4-5 ring rd >5-6 ring rd >2-3 ring rd >3-4 ring rd >2 ring rd,and of the residential area in different loops are as follows: 4-5 ring rd >5-6 ring rd >2 ring rd >3-4 ring rd >2-3 ring rd.The average density of the urban forest in Beijing campus and hospital is 411.7 per hectare and 54.9 plants per hectare,and the average chest height is25.41m2/hm2 and2.23m2/hm2 respectively.The average DBH of the urban forest in each affiliated green space shows that school(23.74cm)> unit(19.97cm)> hospital(17.69cm)> residential area(17.58cm);the average height of trees is: School(7.8m)> residential area(7.76m)> the unit(7.63m)> hospital(6.6m);the average crown size is: School(6.02m)> unit(5.34m)>residential area(5.31m)> hospital(4.65m).(3)The comparison of the indexes between new and old campus in typical schoolThe data of new campus and old campus of Beijing University of Technology,Beijing Architecture University,Beijing University of Chinese Medicine and Beijing University of Posts and Telecommunications were compared and analyzed.The main conclusions are as follows: the UTC and potential UTC of the new campus are all higher than the old campus;the four index values of species diversity(richness index R,Shannon-Wiener index H,Simpson index D,Pielou index J)are lower than the old school area;The number of hectares are higher than that of the old campus;basal area per hectare are lower than that of the old campus.(4)The optimization suggestions of urban forest in Beijing cityIn the construction of campus and hospital urban forest,we should vigorously develop native tree species,choose high biomass and long life species,give full play to the advantages of high ecological benefits.At the same time,it should improve the application ratio of health care plants in hospital,play the auxiliary convalescent function of the hospital green space,and carefully select the tree species that have the hidden danger of plant source pollution.In the process of the configuration of the community structure,we should try to form the complex structure of the compound layer of grass and grass,and consider the landscape effect,the ecological benefit and the social benefit of the community.In view of the large humandisturbance intensity and the small coverage area of the potential tree crown in the school and hospital environment,it can take the form of building a strong adaptable forest and increasing the forms of vertical greening,flower arrangement and potted planting.To expand the green space,in addition,in the construction process of campus forest,we should pay attention to the construction of urban forest culture and give full play to its popular science education function.