The Comprehensive Evaluation And Structure Of Plant Community Of Botanical Garden In3Cities Along Yangtze River

Usually the urban botanical garden possesses diversity manmade communities which composed of introduced plant species from the both local flora and others, in most case, these communities are well designed and maintained intensively and characterized by the relatively stable site. It is apparent that through studying the composition、structure、 dynamic change and landscape value of these communities, we can obtain more information about the disposition rationality of composed species in community, and which may provide useful references for the construction of city green space.In this paper, we investigated the typical plant communities of city botanical gardens in Wuhan、 Shanghai and Nanjing, and analyzed the structure、landscape aesthetics and disposition characteristics of investigated communities. Meanwhile all these communities were evaluated systematically by establishing a scientific evaluation system. Total88sample plots were made, and1654individual trees was accounted.The main results are as follows:(1) Total256tree species were recorded in investigated communities, including87genus and44families of arbor,120genera and59families of shrubs in the investigated communities. Based on the community structure and composition, communities were divided into warm coniferous type, deciduous broad-leaved type, the needle and broad-leaved mixed type, evergreen and deciduous broad-leaved type, evergreen type, accounting for14.77%、19.32%、19.32%、31.82%.14.77%of the community numbers respectively. Obviously, the evergreen and deciduous broad-leaved mixed type (31.82%) had the highest proportion, which indicated the evergreen and deciduous broad-leaved mixed type were more preferred in the Yangtze River Delta region.Typical communities were analyzed in3city botanical gardens according to the important value of the top15main tree species. Although the list of the top15species for the3botanical gardens were different, there are still some coexist and common species, the author found that only the Metasequoia glyptostroboides appeared in these3botanical gardens, Taxodium distichum、Ilex chinemis、Celtis tetrandra、Pterocarya stenoptera、Acer buergeriamtm existed in2of botanical gardens.(2) The photos of88typical community landscapes in the three botanical gardens were taken and related data were collected, then aesthetical value was assessed by the Scenic Beauty Estimation method, and a regression analysis model was established to analyze the beauty influence factors. The results indicated that the communities with score value≥0were well designed for planting, normally evergreen and deciduous species mixed for canopy, and flower brushes or color leaf shrubs as understory, such as Loropetalum chinense var. rubrum、Primus cerasifera var. atropurpurea、Acer buergerianum and Rhododendron spp. The most of these communities had higher ornamental properties and health status.While the communities with score value<0was not in the ideal range and had a chaotic feeling visually, Canopy species were almost evergreen broad-leaved trees and the color was bleak, and also lack of color leaf or flower shrubs for the uderstory so that score was low. Regression analysis showed that the three factors had a significant impact on the beauty of plant community, which was whole landscape coordination degree, community color and brightness, and community health status in order.(3) Using the analytic hierarchy process combined with the quantitative and qualitative indicators the comprehensive evaluation index system was established to evaluate the investigated communities. And the weight for each index was determined by matrix method. The weight rated in order as follows community landscape characteristics=community structure characteristics> community construction and maintenance in the criterion layer weights, and seasonal change、beauty、vertical structure、health status had higher weight in the indicator layer. Based on assessment all evaluated communities were classified as5grades.In Wuhan botanical garden, The grade I accounted for26.92%of the total community, grade II accounted for46.15%, III26.92%, no IV grade in the landscape evaluation results, The comprehensive evaluation values more than60%accounted for73.1%of the total communities;In Shanghai botanical garden, the grade I accounted for15.15%of the total number of communities, II accounted for75.76%, III accounted for6.06%, IV only accounted for3.03%of the total number of communities in the landscape evaluation results. The comprehensive evaluation value more than60%accounted for90.9%of the total number of community landscape.In Nanjing botanical garden, the grade I accounted for34.48%of the total number of communities, II accounted for48.28%of the total number of communities, III accounted for13.79%of the total number of communities, IV only accounted for3.45%. The community comprehensive evaluation values more than60%accounted for82.8%of the total communities.Therefore, the landscapes of these three city botanical gardens were good in general, and15preferable plant community models were summarized up based on the evaluation results.(4) The geographical location of Wuhan, Shanghai and Nanjing three cities are along the Yangtze River. The similarity coefficient of tree species composition was higher between Shanghai and Nanjing botanical garden than that of Nanjing botanical garden to Wuhan’s, or Shanghai botanical garden to Wuhan’s. Meanwhile, Magnolia grandiflora、Castanopsis sclerophylla、Celtis tetrandra、Albizzia julibrissin、Acer buergeriamtm、Liriodendron chinensis、Metasequoia glyptostroboides、Cinnamonum camphora、Platycladus orientalis、Sabina chinensis、Podocarpus macrophyllus totally22kinds of trees and23kinds of shrubs including Camellia japonica、Euonymus japonicus var.aureo-marginata、Elaeagnus pungens、Deutzia scabra Pittosporum tobira、Spiraea cantoniensis、Daphne odora were appreared in three city botanical gardens. These common species were keynote composition tree species of woody communities in city green land of Yangtze River Delta region.Through the analysis of plant configuration features in three city botanical gardens under different site conditions and that beside water4kinds of configuration characteristics and water reflection technique of pavilion were summarized:highlighting the pavilion theme、coordinating with the surrounding environment、enriching the artistic composition、stressing the seasonal aspect, rendering the architecture color.