Analysis On Carbon Fixation Effection And Optimizational Disposition About Plant Communities Of Community Greenspace In Shanghai

Greenland is an important part of the ecological environment, andcommunity greenspace carries ecological function of carbon fixation,oxygen release, cooling and humidification, rainwater conservation,purifying the atmosphere, landscape and recreation, etc. Currently,research on carbon sequestration benefit of community greenspace arelittle, it is urge to build greenspace a quantitative research studies aboutcommunity plant communities. The study regarded plant communities inShanghai community greenspace as the study object. It was based on theinvestigation to plant communities’ characteristics. Plant communitieswere classified. Relationship between plant communities’ characteristicsand carbon sequestration benefits were studied.Combined with characteristics of plant communities which werecommon in the community greenspace, plant communities were studiedby the way of systematic, quantitative and modeling research, hoping tobuild plant communities of high carbon sequestration models. This notonly provided a theoretical basis for optimization of high carbon sequestration tree species selection in the city, but also providedtechnical support for the planning, design and construction work inShanghai’s ecological community greenspace.Three communities greenspace in Shanghai were selected to surveyand a total of60plant communities were investigated in the study.Thesurvey included communities’ characteristics indicators and carbonsequestration benefits, etc. In the same time, plans of plant communitieswere rendered. Data processing and analysising took full use ofstatistical methods and CITYgreen model. And then, the relationshipbetween the plant communities’ characteristics indicators and carbonsequestration efficiency were studied from species composition, canopydensity, hierarchical structure, diameter, density and so on. According toexisting problems for Shanghai community greenspace, the paperprovided suggestions on optimizing the allocation of counter measures.The results showed that:(1)According to the survey of common plant communities inShanghai community greenspace, the60plant communities wereclassified in the case of two different classification criteria. Plantcommunities were clustered into13types of plant communities such asOsmanthus community, cherry community, camphor community, Palmcommunity, Metasequoia community, Ginkgo community, Magnoliacommunity, cedar community, privet community, Magnolia community, Koelreuteria bipinnata community and beech tree communities;according to land use types, plant communities were divided into fourkinds of green types of communities: plant communities in parks, plantcommunities in residential greenspace, plant communities in roads, plantcommunities in other greenspace.The result about plant communities incommunity greenspace showed that: the largest number was thestructure type of arbor, shrub and grass, accounting for75.10%. Theplant communities’ average canopy density was about54%. Averagecommunity density was702every hectare. DBH of trees in differenttypes of greenspace mainly focused on levels of0~10cm and10~20cm,mainly belonged to young forest and mature forest.Community characteristics factors had impact on carbonsequestration benefits of plant communities in Shanghai greenspace:①because of the significant gap among different species, different speciesaffecting the carbon sequestration benefits of plant communities werequite different;②With the increasing of plant communities’ hierarchy,carbon sequestration rate increased significantly: Multi-plantcommunity> double plant communities> single plant communities;③plant communities’ carbon sequestration rate and carbon densityincreased with increasing of canopy density;④plant communities’carbon density increased with increasing of average diameter, the basicrelationship between the two rendered as "S" type, carbon sequestration rate reduced with the increasing of average diameter, the basicrelationship between the two rendered as "anti-S" type.⑤Overall, inthe aspect of carbon density, low-density plant communities weresignificantly higher than the medium-density plant communities, therewas no significant correlation between high and low densitycommunities; carbon sequestration rate of plant communities increasedwith community density increaseing, in another word, high-density plantcommunities> medium-density plant communities> low-density plantcommunities.(3) Pearson correlation analysis about community characteristicsfactors of carbon density and carbon sequestration rate in survey plotsshowed that: there was highly significant positive correlation betweencanopy density and carbon density of plant communities， there was nosignificant correlation between community density and carbon density，there was highly significant positive correlation between carbon densityand average DBH; there was highly significant positive correlationbetween canopy density and carbon sequestration rates, there was highlysignificant positive correlation between community density and carbonsequestration rate, there was highly significant negative correlationbetween carbon density and average DBH; there was no highlysignificant correlation between carbon density and carbon sequestrationrate. (4) Considering plant community characteristics in Shanghaicommunity greenspace, benefits of carbon sequestration surveys andcorrelation on carbon fixation effection of plant communities andcommunities’ characteristics indicators, considering the plantcommunity recreation function and so on at the same time, optimizationmeasures about high-carbon plant communities’ configuration in fourtypes of community greenspace were as followings:①Consideing both visual effects and of carbon sequestrationbenefits of plant communities’ configuration in community greenspace,in the process of design, high-carbon sequestration species were prefered,for example, such as the high efficiency of carbon sequestration trees:the first level arbors, such as Cinnamomum camphora, Pterocaryastenoptera, Magnolia grandiflora, P.×euramericana, Sapium sebiferum,Salix babylonica, Ligustrum lucidum, Citrus reticulate, Camptothecaacuminate and Osmanthus fragrans; the first level shrubs, such asHibiscus mutabilis, Cercis chinensis, Nerium indicum, Photiniaserrulata, Camellia sasanqua and Jasminum mesnyi；the second levelarbors, such as Zelkova schneideriana, Platanus acerifolia, Koelreuteriapaniculata, Sapindus mukorossi, Broussonetia papyrifera, Celtiskoraiensis, Armeniaca vulgaris, Distylium racemosum, Amygdaluspersica, Punica granatum, Michelia chapensis, Prunus cerasifera andElaeocarpus decipiens; the second level shrubs, such as Chimonanthus praecox, Phyllostachys heterocycla, Myrica rubra, Edgeworthiachrysantha, Pittosporum tobira, Viburnum odoratissimum, Buxusmegistophylla, Hypericum monogynum and Nandina domestica.②It was better that canopy of plant communities in communitygreenspace was controlled at50%to70%so that plant communities hadhigher density and carbon sequestration rate.③In the process of plant communities configurationin of communitygreenspace,10~20cm and20~30cm in diameter of seedlings werepreferred to ensure the survival rate of trees and landscape effects.④When the canopy of plant communities was over than60%, theplant communities configuration with low density and high DBH werepreferred; When the canopy of plant communities was less than60%, theplant communities configuration with low-density and high DBH werepreferred.⑤In the process of plant communities configuration in communitygreenspace, we’d better apply the mode of arbor, shrub and grass.