Study On Plant Community Design Of Country Park

Country parks are constructed widely in China at present to control urban expansion, protect natural ecosystems in suburban areas and meet the recreational needs of residents. Focusing on the construction objectives and functional orientation of country park, it is of great significance to explore country park plant community with ecological, landscape and recreational function, for improving urban green space system, creating a natural and rustic recreation environment in countryside.Firstly, based on the overview about the concept, characteristics and types of country park, the features of plant communities and recreation in country park are analyzed. According to the spatial composition of plant communities, the plant communities of country parks are classified into five kinds of space types (open space with visual transparency, open space with visual semi-transparency, vertically enclosed space, horizontal canopy space, fully enclosed space), which is to establish the relationship between plant communities and recreation behaviors as the basis for exploring plant community design. open space with visual transparency, open space with visual semi-transparency, vertically enclosed space are primarily serviced for leisure entertainment, sports and fitness, sightseeing, while horizontal canopy space and fully enclosed space are primarily serviced for leisure entertainment, rehabilitation, arts-and science-based recreation.Secondly, 106 plant communities of country park style in Shanghai and Nanjing are investigated with typical plot survey method, involving 8 parks and parts of the urban green belt of Shanghai, 7 parks of Nanjing. It is found that proportion of horizontal canopy space(32%) and fully enclosed space(43%) are more than others('8%,11%,6% for open space with visual transparency, open space with visual semi-transparency and vertically enclosed space respectively. Because of the terrain differences between these two cities, the proportion of horizontal canopy space of Nanjing(24%) is lower than that of Shanghai(40%), while the proportion of fully enclosed space of Nanjing(50%) is higher than that of Shanghai(38%). Except vertically enclosed space, the other four kinds of space types are rich in vegetation.According to the above investigation, with the methods of Delphi and AHP, a comprehensive evaluation system of country park plant community is established, which involving twelve indicators(species number, local identify, community structure, health status, ornamental characteristics, individual forms, spatial pattern, seasonal change, the pro-green border, environmental quality, activity quantity and recreation facility) of three factors(ecological naturalness, visual beauty and recreational suitability). The weight of each indicator is calculated with group decision-making method based on AHP. Ecological naturalness(0.5481) weighs heaviest, followed by recreational fitness (0.3243) and visual beauty (0.1276). The indicators in the larger weight are healthy status(0.2105), structural stability(0.1472), environmental quality(0.1109), and pro-green border(0.1038).Then, the investigated sample plots are evaluated by the comprehensive evaluation system of country park plant community. The evaluation result shows that the average score of open space with visual semi-transparency(7.09) is significantly higher than the other four space types, followed by open space with visual transparency(6.75), horizontal canopy space(6.52) and vertically enclosed space(6.51)and fully enclosed space(6.18). For the factor of ecological naturalness, fully enclosed space gets the highest score, while vertically enclosed space gets the lowest score. For the factor of visual beauty, vertically enclosed space gets the highest average score, while horizontal canopy space gets the lowest score. For the factor of suitability recreation, open space with visual transparency gets the highest average score, while full enclosed space gets the lowest.Consequently,on the basis of the above evaluation results and main function of each space type, optimization strategies for the plant community design of Shanghai and Nanjing are put forward correspondingly. For the open space with visual transparency and open space with visual semi-transparency, the species quantity of bush and tree should be added, and lawn border should been designed exquisitely. Near natural mixed grass should be applied to replace the current grass with a main species and local herbs, which can enhance the self-stability of plant community and reduce maintenance costs.Vertically enclosed space is serviced for special class garden and tour path. Enriching the specie of shrub and adding signs are helpful to enhance science educational function of special class garden and fun of tour path. Horizontal canopy space and fully enclosed space take a larger proportion in the country parks. Small trees, low shrubs and flower with rich ornamental characteristics should be planted at the forest edge. Setting explicit and implicit sign at the boundary help visitors to walk into the inner space of plant community for experiencing the ecological beauty of forest. Periodically removing weeds and enrichment of artificial grass should be applied to ensure the clean and aesthetic ground. In order to increase the light transmission distance of the forest perspective, thinning and cutting of trees can be adopted suitably. Heterogeneous mosaic of the spatial pattern should be designed to create rich spatial forms for meeting the recreational needs from different visitors.