The Study On Risk Assessment And Management Of Urban Forest In Beijing

Urban forests is the primary producers of urban ecosystem, which is the backbone of ecological balance of the city. It plays an important role in purifying the atmosphere, regulating urban microclimate and improve life quality of the residents. However, urban resources and environmental issues are becoming increasingly serious, with the rapid development of urbanization in China. The urban forest is faced with forest fires risk, the damage risk of pest and all kinds of risk caused by city expansion and urban construction, In order to realize the sustainable management of the urban forest sustainable development of society, we must follow the ecological laws and socio-economic laws to manage urban forest risks scientifically.The methods used in the research include:(1) the model of Information Diffusion Theory is used to calculate the probability and cycle of the urban forest fires.(2) Gray Model GM(1,1) is applied to predict the relevant risk indicators.(3) the improved method of loss coefficient is used to estimate the direct economic loss of urban forest pest risk.(4) the theoretical area of urban forest is calculated according to the domestic and international standards and the method of carbon and oxygen balance.(5) the Entropy Coefficient Method is applied to assess the urban forest risks comprehensively.(6) measure the urbanization level in Beijing by using population proportion index method.The main content of the research includes:(1) assess the fires risk and the damage risk of pest of urban forest systematically, including risk identification, risk analysis, risk prediction and loss measurement.(2) research the risk of urban system interference including supply and demand risk, forestry land risk and structural risk of urban forest. And sort the risk of districts and counties of Beijing.(3) the comprehensive evaluation system of urban forest risk is established, including5second class indicators and13third class indicators. Evaluate and sort the comprehensive risk of urban forest in Beijing counties and functional areas by using the Entropy Coefficient Method.(4) analyze the increase and decrease of urban forest risk indicators quantitatively under the different growth of urbanization.(5) summed up the management nature, principles, content, process and security system of urban forest risk systematically. And make recommendations according to the problems presented in the research.Major results of the study include:(1) the probability of which forest fires occurs more than1～4times a year is greater than85%in Beijing. The number of forest fires is about1-2per year in the next five years. And the predicted forest harmed area value is2～5hm-per year. The value loss of soil conversation is maximum in ecological service function affected by the fires, and in which nutrients accumulation is minimum.(2) the total area of forest diseases and insects will increase year by year. The direct economic loss of polar defoliators is maximum in forest pest risk from1998to2012in Beijing. Direct economic loss is maximum in2012. The ecological services value loss is maximum in2008, which is in11.34percent of the total loss.(3) the risk in Xicheng District, Dongcheng District, Chaoyang District is maximum in urban supply and demand risk and forest land supply risk ranking of all counties in Beijing. Forestry land area in2020may decrease by16.27%over2012. And urban forest of Beijing is faced with forestry land occupied risk.(4) according to the comparison of comprehensive risk value of urban forest risk, the comprehensive risk value in Fangshan District is maxmium, which in Pinggu District is minimum. And comprehensive risk value in city development zone is maximum, which the core functions of the capital area is minimum.(5) with the rapid development of urbanization, the probability of occurrence of forest fire risk will decrease, and which of urban forest pest risk and urban system interference risk will increase.