| In recent years, too much emphasis on the visual effects and ornamental value of plants is placed to landscape in many cities, therefore a large number of the introduced exotic ornamental plants are adopted, while the application of indigenous plants is ignored, resulting in the situation that the urban landscapes are all the same and lack local characteristics. Large scale introduction of alien plants is may destroy the city’s ecological environment and reduce biodiversity. Indigenous plants not only have the characteristics of strong adaptability and stress resistance, but also are easy to maintain and manage, and won’t damage the ecosystem easily and can form regional landscapes. Therefore, more indigenous plants shall be introduced for the urban landscapes.Although landscape architects have been promoting indigenous plants and use more indigenous plants, and the relevant government departments have also recognized the importance of indigenous plants, the studies of indigenous plants are few, and which selection criteria should be applied in practice is still uncertain. In order to provide a scientific basis for the selection and application of indigenous plants in urban landscapes in the future, this paper studies the urban landscape architecture suitability evaluation system based on the study of indigenous plant species in Changsha, and sets up an urban landscape suitability evaluation system of indigenous plants with Changsha indigenous plants as the subject, and works out the urban landscape suitability index of Changsha indigenous plants, and finally decides on the species of indigenous plants which can be used in urban landscapes according to the suitability index.(l)The survey makes statistics for158families,619genera,1116kinds of indigenous plants in Changsha City, and prepares the Changsha indigenous plants directory. In the outskirts of the city, the standard sample plot survey method is employed, which selects20standard plots from four forest parks including Qingyang Lake, records the species, number, height and diameter of arbor, the types, number, breadth and height of shrub, the types and area of herb. Inside the city, the sample survey method is employed, which selects the typical places from city parks, residential areas, enterprises and institutions, urban roads respectively to carry out the survey of indigenous plants. According to the survey, Changsha indigenous plants have the following characteristics:①There is a variety of indigenous plants, there are29large families including more than10species;②The indigenous plant species that have been applied to urban greening are only10.26%of the indigenous plant species;③The application proportion of indigenous plants in Changsha urban landscapes is very small, accounting for only27.08%of the Changsha City urban greening tree species.(2) Depending on the determination of the carbon fixation and oxygen release, cooling and humidification capability, there is no consistent differences of capabilities between indigenous plants and exotic plants. The carbon fixation and oxygen release, cooling and humidification capability of plants associated with species, and there is no direct relationship with source. There species of evergreen native arbors-Manglietia fordiana, Cinnamomum camphora and Eelaeocarpus glabripetalus, and there species of evergreen exotic arbors-Manglietia moto, Michelia chapensis and Michelia cavaleriei are measured in the same site conditions, at similar ages and growing conditions. The carbon fixation amount of the evergreen native arbors on per unit of land are respectively57.58g·m-2d-1,58.67g·m-2d-1and28.54g·m-2d-1; the oxygen release amount of them are respectively52.35g·m-2d-1,42.65gm·2d-1and20.75g·m-2d-1;the humidification amount of them are respectively12132.90g·m-2d-1,17882.68g·m-2d-1and13081.82g·m-2d-1; the cooling amount of them are respectively2.34℃,3.44℃and2.52℃. The carbon fixation amount of the evergreen exotic arbors on per unit of land are respectively49.42g·m-2d-1,31.86g·m-2d-1and44.77g·m-2d-1; the oxygen release amount of them are respectively44.92g·m-2d-1,28.97g·m-2d-1and40.70g·m-2d-1; the humidification amount of them are respectively10729.84g·m-2d-1,7929.44g·m-2d-1and10326.53g·m-2d-1; the cooling amount of them are respectively2.07℃,1.53℃and1.99℃. According to the measurement, the carbon fixation and oxygen release, cooling and humidification capability of plants associated with species, and there is no direct relationship with source. Moreover, the carbon fixation and oxygen release amount and cooling and humidification amount of6species of deciduous arbors, evergreen shrubs and deciduous shrubs are measured, similar results are obtained to the evergreen arbors.(3)The abundance index and diversity index of the community dominated by indigenous plants are higher than the communities dominated by foreign plants. Calculated with Gleason index and Simpson diversity index, the abundance index and diversity index of the community dominated by indigenous plants are2.0028,2.1698,1.8359,3.1712and0.8061,0.8405,0.8065,0.8473; the abundance index and diversity index of the community dominated by exotic plants are1.8359,1.6690,1.0014,1.1683and0.7135,0.7631,0.6432, 0.5931. The community dominated by indigenous plants is more complex in structure, more obvious in level, and much higher in biodiversity.(4)It sets up the suitability evaluation indicator system of indigenous plants to urban landscapes. Evaluating indicators are collected as many as possible with the principle of combining science, systematic method, simplicity, representativeness, comparability, applicability, qualitative indicators and quantitative indicators together through gathering and arranging the literatures relating to the research of domestic indigenous plants based on the research on urban garden esthetics. Through brainstorming, the Delphi method, and in-meeting&after-meeting method, after four rounds of indicators screening, finally three first-level indicators, four secondary indicators, and24third-level indicators are determined as suitability evaluation indicators of indigenous plants for urban landscapes. The score of24indicators multiplied by their weights is defined as the suitability index of indigenous plants for urban landscapes. The suitability is represented by the index measured using the percentage system and it is attached with different scores measured by the weight of the individual indicators. Depending on the suitability index of indigenous plants to the urban landscapes, the suitability level of indigenous plants to urban landscapes is divided into five levels-Ⅱ, Ⅲ, Ⅲ, Ⅳ,Ⅴ respectively, representing very good, good, average, poor, very poor.(5) It evaluates the suitability of indigenous plants in Changsha urban landscapes and determines the importance of the various indicators with the expert scoring method. Besides, it also determines the weight of each evaluation indicator to the suitability evaluation of indigenous plants in Changsha landscapes by analytic hierarchy process, quantifies each index by weights, determines the index value by percentile, and divides each index into three levels, each having certain score, and finally decides the suitability evaluation indicator system of the indigenous plants in Changsha landscapes.(6) It recommends381kinds of indigenous plants for Changsha City. There are30kinds of pteridophytes,8kinds of gymnosperms, and343kinds of angiosperms among them.(7) It studies the landscape design of indigenous plants in the three types of urban green land, namely park, green buffer and attached green land. It selects appropriate types of indigenous plants to the features of green lands respectively based on four species, namely arbors, shrubs, vines and ground vegetation according to the features of various types of green land, with reference to the suitability indices and indicators scores, and makes corresponding plant community combination for each type of green land for reference and application. The main innovations include three aspects:(1) It introduces the concept of "suitability indicator" to the application of indigenous plants in urban landscapes, establishes the suitability evaluation indicator system and evaluation model for indigenous plants in urban landscapes, and decides to conduct suitability evaluation of indigenous plants for urban landscapes with indicators at different levels; wherein, level one indicator includes arbors, shrubs, vines, and ground vegetations; level two indicator mainly includes the ornamental value, ecological effect, introduction breeding, and maintenance management; and there are also24level three indicators. Through calculating the product of the scores of24indicators and their weight, the accumulated value is defined as the suitability indicator of indigenous plants in urban landscapes.(2) It determines the importance of each suitability evaluation indicator of the indigenous plants for landscapes in Changsha with expert scoring method; works out the suitability evaluation indicator system of indigenous plants for landscapes in Changsha through the analytic hierarchy process; calculates the suitability index of1,116kinds of indigenous plants surveyed in Changsha, and then recommends381kinds of indigenous plants.(3) With reference to the suitability index and the index score, based on the features of various types of green lands, it selects appropriate indigenous plant species for the green land respectively based on four specifies, namely arbors, shrubs, vines, and ground vegetations. |
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