Study On The Landscape Tree Species And Plant Allocation Mode Of Urban Forest In Chengdu

With the continuous accelerating of the urbanization,urban environmental problems becoming increasingly prominent,urban ecosystems are under increasing pressure,the study of urban forest has gradually become a hot spot.This paper took urban forest as the research object,which is in central city area of Chengdu,based on the data collection,field survy method and questionnaire survey method,established the evaluation index system of landscape tree species and plant allocation mode by Delphi method and analytic hierarchy process(ahp),put forward suggestions for optimization of the different urban forest,in order to provide reference frame for Chengdu urban forest construction.The main research results are as follows:(1)based on five aspects of landscape tree species,which are biological characteristics,landscape function,ecological function,cultural function and economy degree,with questionnaire survey method,Delphi method and analytic hierarchy process(ahp),this paper constructed the functional evaluation index system of landscape tree species.evaluation indexs included suitability,resistance,tree shape,leaf shape and color,dust detentions,cooling and humidifying effect,cultural connotation,protection value,the cost of the maintenance,etc.The evaluation results showed that,biological characteristics and economy degree of tree species in the Chengdu urban forest are generally better,the landscape function and ecological function indexes were greatly different,and the cultural function of most trees were insufficient.Height class landscape tree species with better various index are Hibiscus mutabilis(88.95)?Liriodendron chinense(88.10)?Ginkgo biloba(86.75)?Cinnamomum camphora(86.26)?Koelreuteria paniculata(85.94)?Phoebe bournei(85.82),etc.These height class landscape tree species are relatively good on the ecological function,landscape function,cultural function,but their species number in the 78 landscape tree species is only 24% of the landscape tree species.According to the different index advantages of landscape tree species,they are recommended to different urban forest environments.(2)based on three aspects,which are forest stand quality,forest stand function and economy degree,with questionnaire survey method,Delphi method and analytic hierarchy process(ahp),this paper constructed the comprehensive evaluation index system of plant allocation mode,evaluation indexs included health degree,stability,ecological protection function,landscape recreation function,space utilization rate,community maintenance cost,etc.Different urban forest types of plant allocation mode evaluation results showed that 1)In urban suburban forest,the highest score of them are Phoebe bournei-Ulmus pumila forest(87.68)?Cupressus funebris-Quercus acutissima forest(84.85)?Cinnamomum camphora-Ginkgo biloba forest(84.55),and the lowset score are Amygdalus persica forest(45.73)?Eriobotrya japonica forest(44.62)and Pyrus pyrifolia forest(42.53),They were also the highest and lowest of all surveyed plant allocation mode,which explain the great differences between that plant allocation mode,suburban forest has a better forest stand quality,but part of the plant community structure is relatively monotonous.2)Urban park forest has good landscape recreation function and cultural heritage function,seasonal effect is obvious,space utilization rate is high,but the use proportion of Chengdu native tree species is not high,maintenance management cost is higher.3)Urban river forest has a strong ecological purification function,it has a certain proportion of hygrophilous plant species,but the herbaceous species repeatability is strong.4)In urban road forest,most of the plant community have a higher ecological protection function,but repetition rate of upper tree species is high,the structure of some patterns is too close or too sparse.(3)Combined with evaluation results of landscape tree species and plant allocation mode,put forward suggestions for optimization of urban forests in Chengdu: 1)Urban suburban landscape forest emphasize the ecology of plant allocation mode,enrich the monotonous plant community structure,increase high grade tree species with good ecological function and cultural function.2)In urban park forest,improve the utilization rate of land resources as the primary goal,enhance the seasonal effects and ecological functions of plant communities,needs to increase the use proportion of native tree species.3)Urban river forest should strengthen its ecological purification function,enrich herbaceous species.4)Urban road forest needs to enrich the upper tree species,strengthen the ecological protection function of tree layer,and adjust the structure that is too close or too sparse.