Multi-Objective Planning Of Urban Forest Ecological Network In Wuhan

The rapid urbanization triggers various urban problems, such as resources shortage and ecological environment deterioration. Especially, the fragmentation of forest landscape severely restricts the regional sustainable development. Urban forest ecological network with optimized structure and function can play ecological, environmental, social and other functions. It can achieve a balance between ecological protection and economic development in cities with very limited land resources, and promote the sustainable development of man and nature. Thus how to construct a multi-functional integrated urban forest ecological network has become an important issue to be solved.Took Wuhan as a case study, with the application of the theory and method of landscape ecology and the technology of remote sensing and geographical information systems, we explored the multi-objective integrated planning of urban forest ecological network in Wuhan. By analyzing the needs of Wuhan, we determined the biodiversity conservation, water environment protection and urban forest recreation services as the planning targets. Firstly, we constructed the single target-oriented ecological network, and then overlaid and integrated these planning schemes, finally we obtained the multi-functional integrated planning scheme of urban forest ecological network in Wuhan. The main results are as follows:(1) Took the Mustela sibirica, Syrmaticus reevesii, Turdus merula as surrogate-target species, integrated multi-criteria analysis of habitats and least-cost path model, we constructed an ideal conservation network for single target species. Furthermore, we applied kernel density estimate to plan a priority network for overall biodiversity conservation. The ideal network configuration of Mustela sibirica contains 195 habitat patches with an area of 560.66 km2 and 3125 potential corridors with a total length of 4021.58km. The ideal network of Syrmaticus reevesii consists of 250 habitat patches and 3970 potential corridors. The total area of habitat patches reaches to 560.65 km2, and the corridor length is 4711.5km. While for Turdus merula, the ideal network is composed of 627 habitat patches and 9287 potential corridors, its habitat area is 632.96 km2 and the total corridor length reaches to 7403.58km. Approximately half of the area of the existing urban forest patches need to be protected as habitat. The habitats of three target species are all concentrated in the north, northeast and southern hills and forest parks of Wuhan, but there is little distribution in the main urban areas, only scattered in the suburbs. Also their corridors distribution are similar, mostly distribute in the suburbs, and in the north, southeast, southwest the corridor density is higher. Finally, based on kernel density estimating, we generated a priority network for overall biodiversity conservation. The form is a combination of ring structure and dendritic morphology. Near the Out Ring Road forms a big ring, beyond which is the dendritic corridors connecting habitats patches. The potential utilization of this ring is the most highest, so it has the top priority for biodiversity conservation network construction.(2) Combined the buffer analysis and land use types, we planned protection corridors for main water resources in Wuhan. Then the overall construction of water environment protection corridors has been greatly improved. For water resources with an area bigger than 10 km2, its corridor area reaches 10617.98 hm2, accounting for 45.91% of the ideal configuration area. For water resources with an area between 1 and 10km2, the corridor area is 5870.15 hm2, the construction proportion is 57.87%. While for those with an area between 0.2 and 1 km2, the corridor area is up to 831.94 hm2, taking up 29.83% of the ideal configuration area. The construction ratio of overall water environment protection corridors is up to 48.03%, and the main components are forests. And we mainly constructed the river protection corridors. The construction proportion of Yangtze River and Han River are both more than 60%, others such as the Sheshui River, Daoshui River, Jushui River, Jinshui River, Dongjing River, Tongshun River, Sha River and other major rivers are more than 80%.(3) Based on the source and sink analysis of urban forest recreation process, we constructed the least-cost path model and then planned the urban forest recreation network by self-driving in Wuhan. The total length of corridors is 888.91km. The Out Ring and Middle Ring Road form two obvious rings, combined with the radial highways and urban main roads form a green network connecting inside and outside the city effectively. Through recreational resources and environment background analysis, we determined the bicycle recreation corridors. We planned four bicycle recreation corridors with a total length of 110.78km. They are Changqing-Boquan Farm, length of 23.56km; Zhuankou-Nine really Forest Park, length of 31.44km; Optical Valley - Longquan Mountain Scenic Area, length of 25.04km; bicycle ring road of East Lake Scenic, length of 30.74km.(4) Overlaid and integrated the single target-oriented ecological network and then generated a strong and complex network configuration, we expected to achieve multi-functional objectives. Biodiversity conservation and water protection networks will have bilateral promotion; while for recreational network, we need to take proactive measures to reduce human disturbances, and then coordinate with other functions.Through case study in Wuhan, we explored the approach to achieve the target-oriented planning of urban forest ecological network and multi-functional network integration. We expect to provide a scientific basis for decision making of ecological construction in Wuhan, in addition, to provide an example for other cities in the planning and construction of urban forest ecological network.