Study On The Optimization Of Green Infrastructure In Yongding District Based On The Evaluation Of Ecological Service Function

The rapid development of economy promotes the process of urbanization,but it also brings serious ecological problems.It has become an important task for human society to alleviate the trend of environmental degradation and promote the sustainable development of ecology,economy and society.It is also an unprecedented challenge for mountain cities with prominent contradiction of human and land.Green infrastructure is a kind of ecological network system composed of natural and semi natural areas,which can provide a variety of ecological services for the benefit of human beings.With the trend and opportunity of vigorously promoting the construction of ecological civilization,it shows a huge application prospect and its importance is increasingly prominent,and it has become a key element for the maintenance of ecological environment and the repair of ecological problems.In the past two decades,many scholars have used ecosystem method as a tool to deal with climate change and environmental problems,which has made ecosystem method widely studied and promoted.Face to the sustainable high-speed development of social economy,the author thinks that we should embed the ecosystem method into the theory and practice of the green infrastructure plan of mountain cities,and use the ecosystem method to evaluate the current situation of the ecological service of the green infrastructure in the region,so as to optimize the green infrastructure in the region and make a positive and beneficial plan for the green infrastructure of mountain cities for promoting the sustainable development of natural environment and ecology in mountain cities.This paper studies the ecological service function of green infrastructure,defines the concept of green infrastructure and ecological service function,and uses Invest model(Habitat Quality)and Xie Gaodi's equivalent factor method to evaluate the ecological service function of green infrastructure in Yongding District,Zhangjiajie City,to clarify the current situation and problems of green infrastructure,and to discuss the ecological service value's distribution and ecological environment of green infrastructure in Yongding District,to put forward the optimization pattern and suggestions of green infrastructure in Yongding District.The main conclusions are as follows:(1)The overall habitat of green infrastructure in Yongding District is in good condition,but the habitat quality is interfered by human activities.The proportion oflow value areas in the habitat index increased from 2.01% in 2015 to 4.96% in 2017.The overall habitat quality of green infrastructure shows a declining trend,especially around the urban area of Yongding District.Due to the continuous expansion of urban construction,it encroaches on the farmland and green land in the surrounding areas,resulting in the deterioration of the habitat quality.At the same time,the habitat quality's degradation of Yongding District is becoming more and more serious.The rapid degradation areas and the range of severe degradation areas are both increasing rapidly.In terms of proportion,the proportion of rapid degradation areas increase from 0.93% in 2015 to 1.71% in 2017;the proportion of severe degradation areas increase from 6.02% in 2015 to 8.15% in 2017.From the perspective of space,the serious degradation areas are expanding from urban areas of Yongding District and surrounding towns,which forms a degradation circle with the central area radiating the surrounding towns.(2)The ecological service function of green infrastructure in Yongding District is good in general.From the perspective of space,the value of ecological service gradually increases from the inside to the outside with urban area as the center.From the perspective of topography,the overall service function of mountain and forest land is relatively high,and the total value of ecological service reaches 126,703,400 yuan;while the plain and hilly areas are relatively low,the service value of mountain and forest land such as Zhushitou forest land,Maoyanhe scenic spot,Xuanshui forest land and Shichangxi forest land in the north is significantly higher than central hilly and plain areas.From the perspective of ecological load-bearing capacity,green infrastructure such as farmland and water areas is fully utilized within the threshold of ecological load-bearing capacity;mountain and forest land have a high ecological load-bearing capacity,and the service value of forest system is only 126,703,400 yuan when its threshold is 676,071,200 yuan,which indicates that the single structure of forest land and the lack of effective corridors to connect the patches of surrounding environment in this area restrict the effective play of the ecological service function in the region.(3)Based on the evaluation results of ecological service function of green infrastructure in Yongding District,this paper optimizes the ecological network of green infrastructure in the District,and puts forward the optimization pattern of ecological network of green infrastructure in "two belts,two axes,five districts and five groups",and emphasizes that the green infrastructure in Yongding District should pay attention to the time sequence,take different optimization strategies to improvethe effectiveness of the network according to the different needs of different regions,Strengthen the dynamic links between green infrastructure.