| Urban forest is the most vital eco-system and landscape in urban area,which includes diversify eco-service function(such as water conservation,wind and dust retention,bank protection,beautification,leisure,entertainment,etc.).With the development of city and the improvement of residents' living-standard,the urban area request more for urban forest.In Shanghai,there are fewer forest resources and lower forest cover rate.Since the reform and opening-up,especially in the past two decades,Shanghai focused on the urban eco-construction and built a certain scale of man-made forest which had positive effects on urban eco-environment.However,due to the time limit and the lack of strict standards during that period,the community structure of man-made forest was simple and low in biodiversity,commonly known as "nursery forest" and "big seedling forest".The rigid man-made forest ignored the rationality of the inner structure.As time went by,the health problems within the forest became increasingly prominent,and the landscape effect could not be fully functioned.This article built a multi-target forest eco-system health evaluation index system for urban area,which based on the classification method for the purpose of management: evaluating health for urban forest ecosystem by structural index,vitality index and ecological function index of different forest species;the theory that structure determines function,which means different evaluation indicators were selected to indicate ecological functions: analytic hierarchy process(AHP)in combine with experts scoring method were used to determine the weights of each index.According to the 2015 forest resource survey data and the 2018 field sampling survey of the forest community in Fengxian District,a case study on forest ecosystem health assessment of 8 sub-type of urban forest was carried out.125 plots in total were selected for field research.The results showed that Fengxian urban forest was in a sub-health state,which healthy plots,sub-health plots and medium-health plots accounting for 8.73%,61.9%,and 28.57% respectively.For different forest species,the windbreak forest has good quality,and the healthy sample plot accounted for 50%,followed by the germplasm forest,and the healthy sample plot was 33.33%.All the proportion of healthy plots in landscape forest,environmental protection forest and water conservation forest was less than 10%.Then,the principles of landscape ecology and ecological conservation were used in this article,which following the experience of urban forest construction from both domestic and abroad to discuss the resource optimization and management of Fengxian urban forest resources.According to the evaluation results,the key nodes of Fengxian urban forests were high health level and excellent ecological benefits.Combined with the existing water network and road network,the key corridors of Fengxian urban forests are identified based on minimum cost,optimal sample plot and optimal connectivity,which constructing a key ecological network of Fengxian urban forest.Combined with the evaluation results of Fengxian urban forest,the crux of ecological damage of vegetation community in nodes and corridors was found,and the causes of damage were analyzed.The suggestions for solving community health problems or functional loss of forest type with different functional were proposed.In summary,this study constructed a multi-objective urban forest evaluation index system which is suitable for the rapid urbanization areas,evaluated the urban forest health in Fengxian District,identified the key nodes and corridors in the urban forest ecological network,and proposed specific optimization measures based on the evaluation results.This study improves the method system of urban forest ecosystem health evaluation,and provides feasible plans and suggestions for the realization of urban forest health in the region,which is of practical significance for the sustainable development of the city. |
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