Landscape Pattern Analysis And Optimization Of Green Space System In Center Regions Of Chengdu

The urban green space system improves the air quality, reduce heatingisland effect, purifies and preserves water reservoirs, hence it is vital for development of suitable ecological environment. The urban green space system is the key of planning on constructing the ecological city. The current status and landscape pattern of city's green space system were analyzed and evaluated in order to provide the scientific basis on optimization pattern and the ecology plan of the city green space system.The landscape images were gathered from Google Earth satellite images, and edited by some software, such as CAD, Photoshop. The paper focuses on Chengdu center regions' green system. Based on Arcview technique and landscape ecology theories and methods, some techological and landscape pattern indexes were analyzed to evaluated the current status of center region's green system. Based on those analysis, the current status of green systems in different regions were compared, and carried on the suitability analysis to the city land, the suggestions which was about optimize of landscape pattern was proposed. The results of the study provided guidelines for transformation of urban built up area, planning of L'Eixample and scientific management of urban green space.The result indicated as follow:(1) The total green coverage of Chengdu was larger(22544.06hm~2), percentage of greenery coverage basically achieved the standard of the national garden city, but the per capita also had disparity. The number of green patches was more, attached green space whoes average area was smallest (0.2hm~2) occupied the absolute superiority. In the green space system, lacked large-scale green space., the quantitative proportion of large and middle scale green patches was only 25.21%, including the massive productive plantation area and scenic forest land in surburbs.(2) Patch Shape Index, Fractal Dimension and Shannon-Wiener Index respectively is 1.598, 1.160 and 1.388, explained the shape of green patches was regular, the Landscape Diversity was low. The landscape pattern indexes of various types of green space indicated that, green buffer whoes Patch Density index was 2.287 can't play protection function well. Line Corridor Density index and network connection were low, respectively was 37.99m/hm~2 and 0.439, corridor lacked good connection, had not formed the good network architecture. The third contour current status was compared with the others, showed that the average area of each type of green space was bigger,the patch fragmentation was lower and the landscape diversity was higher. But the third contour also existed the quantity of attached green space occupied the absolute advantage, which made known that the urbanisation already launched in the third contour. For each administrative district's nature is different, construction of green space also has the difference. Qingyang district is the cultural center, the quantity and area proportion of public park was bigger than the other districts'; As main commercial and dwelling community, High &New Technology Zone and WuHou district's attached green space had the largest numbers, caused the patch fragmentation was serious, respectively was 1.957 and 1.373. Chenghua district was the old industrial area, had few public park , is lacking green buffer , also has high broken degree . Jinjiang district has many surburb green space and scenic forest land ,whose area hold major in the district, caused the area of various types of green landscape distributed unevenly and the landscape diversity (4.098) was lower than to other several areas.(3) The suitability analysis showed, in the city core area the flinty paving occupied the major area, only had little grit surface and the artificial water percolation paving in the city and around the city network of waterways is suitable as the afforesting land. The mainly suitable land for urban green space construction concentrated in the boundaries of the city third contour and in the highway-ring. green space was constructed on the suitable land, the investment cost should be less.(4) Through city green space landscape pattern optimization, the level of urban green space was enhanced: the total green space area and connection were increased, the patch fragmentation was decreased. Linking up the block, the corridor, the wedge, the garden and the belt, gathering points, lines, planes, rings and nets, has formed "one belt—seven wedges—three rings—several gardons" green space layout. The outer ring greenbelt stringed several large-scale forest parks and scenic forest land on the surrounding of urban center region of Chengdu, which can be formed as a natural barrier for the city, prevents the city infinite spread; The green wedge inserts in the city, strengthened the relation of city and countryside's natural elements, also has prevented the city expansion axis merge; The green space was perfected on River corridors, the city contours and expansion axis, was constituted network, what connected each grade of public park in the city, strengthened the matter and energy flow of ecosystem, promoted the stability of ecology function, formed the relatively stable landscape pattern, has enriched the city landscape.