| With the acceleration of urbanization, urban green space system plays an increasingly prominent role in easing the city pressure, improving the ecological environment, promoting the city industry transformation and other similar aspects. Development of geographic information system and remote sensing technology provide technical support for the optimization of urban green space system in small cities, and the strategies of sustainable development and balancing urban and rural development have also provided policy support for them, many cities are taking this opportunity to actively carry out the urban green space system optimization and construction. Based on the Pleiades satellite images in 2014 and aerial images in 2011 of Lengshuijiang city in Hunan Province, this paper has selected six indicators of National Garden City to calculate the urban green space area index of this resource city, analyzed the accessibility of its parks by the network analysis method and evaluated the green area landscape pattern by using landscape ecology theories and methods. And then this paper has analyzed the urban green space construction of Lengshuijiang on area quantity, service quality and ecological quality aspects by using Arc GIS. Hope that the results can contribute to the urban green space system optimization of Lengshuijiang city and the similar small city in resource type. The main conclusions are as follows:(1) The urban green coverage of Lengshuijiang built up district is 37.14%, the green space ratio of it is 33.45% and the park green space area per person is 16.26 m2, these three indicators have all reached the national standard of garden city, especially the park green space area per person is significantly higher than the national standard. However,the green space compliance rate of the new or renovation residential area(92.76%), the implementation rate of protective greenbelt(70.02%) and the riverfront construction rate(46.78%) of this city are all under the national standard, especially the implementation rate of protective greenbelt is almost lower 10% than the national standard,and the riverfront construction rate is lower more than 30% than the national standard, these kinds green space is in urgent need to improve. The park green space area of the sub classes are disparities, the number of community park, linear park and street green space is abysmal lack; attached green space ratio is too small; there is a serious imbalance between industrial protective greenbelt ratio and railway protective greenbelt ratio, the other green space ratio is relatively high. Above all, this paper puts forward these green space optimization measures as that focus on strengthening the riverfront green space transformation of Lianxi River, strengthen the river green construction, increase the area of industrial protective greenbelt and waterfront linear park when constructing the ecological revetment of the river. So that the protective greenbelt implementation rate can be arrived to 83.70%, which has reached the national standard; the riverfront construction rate can be arrived to 67.04%, which has improved about 20% compared with before; and the adjacent Riverfront linear Park which is near the residential area can ease leisure space less and greatly improve the using efficiency of urban green space.(2) The accessibility analysis of park green space shows that in Lengshuijiang built up district, the most comfortable walking distance(10min, Service Radius 500-600m) of public green space service area for people is concentrated on both sides of the Zijiang River, there is a public green space service fault distance of most suitable for walking along the Middle Tidu road in the old city, there is non service area of public green space above 30 min accessibility between Lengshuijiang steel plant and the City East Ring Road. The most area of the city new town in the east of Zijiang river is not in the range of 10 min public green space accessibility. The public green space service scope of planning central city has almost covered all of the city range, the public green space area has been significantly improved compared with built up district, but in the edge of the central city there is still a certain proportion non service area of public green space, even to the extent that the public green space service area ratio of the planning central city has decreased by about 10% than the built-up district. So it is necessary to strengthen the construction of public green space which is within 10 min walking distance, and actively promote the natural forest in the central city into the urban public green space to complement the public green space service area above 30 min. At the same time, the city should focus on these optimization measures including increasing the existing park entrance number, strengthening the construction of vertical greening, adding pocket park and constructing a city slow traffic system to improve the service efficiency of urban public green space in nearby distance, and through the rational use of natural mountain forest to add the country park to improve the service efficiency of urban public green space in long distance.(3) The small green patch number ratio of Lengshuijiang city is extremely high, accounting for 80% of the total green patch number, most of these small green patches are attached green space which is closely related to the residents’ daily life. Large green patches have absolute superiority in the area proportion, most of them are city parks that landscape dominance index of them is 48.2%. The attached green space landscape dominance index is in the second, but the fragmentation index of it has reached 66891.13 in the old city and 30473.67 in the new city, which are significantly higher than park’s fragmentation index both in the old city and the new city(455.44 and 8.44). The productive plantation area landscape dominance index is the lowest, only 0.4%. Protective greenbelt landscape dominance index is slightly higher than productive plantation area, but the fragmentation of it is serious, only better than the attached green space, it is particularly evident in the old city. Other green space landscape dominance index is high(19.1%), its fragmentation is just same as park green space. On the whole, the fragmentation index of all kinds of green space in old city are significantly higher than that in the new city. The fractal dimension of every green space is generally low, the artificial interference degree of them is high, the whole landscape diversity is small, and landscape diversity of the old city is slightly less than that of the new city. So that,the ecological quality optimization strategies are about the follow tow aspects. First, we should take the "micro-improving" measures for different types of green space to improve the urban green space landscape structure; and then we should use the "macro-control" measures to construct the city green space ecological network in different scales, in order to adjust the pattern of the urban green space system of Lengshuijiang from the macro regulation.Based on the urban green space system analysis and evaluation of Lengshuijiang, ths paper has taken a more in-depth discussion on the urban green space system optimization strategies of Lengshuijiang, and the urban green space system planning methods and development of the similar small city in resource type. |
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