Study On The Evaluation Of Forest Ecological Security In Linzhi

The functional benefits of the forest ecosystem greatly affect the functioning of the ecological security barrier in Tibet.Tibet’s forest resources are mainly concentrated in Linzhi City,Linzhi forest ecosystem plays an important role in the ecosystem of the Qinghai-Tibet Plateau.Based on the importance that the Party and the state attach to the ecological environment of the Tibetan Plateau and the reality of the vulnerability of the forest ecosystem in the Tibetan Plateau,it is of strong urgency and practical significance to explore the forest ecological security situation in Linzhi City.In order to clearly understand the current situation and security situation of forest resources in Linzhi City,this study took Linzhi City as the research area,used multi-year climate thematic maps,the seventh national forest resource inventory data,and combined with socio-economic data,conducted a quantitative study and analysis of the forest ecological security situation in Linzhi City in 2008 using the PSR model,in order to provide a decision-making basis for forest ecological construction in Linzhi City.The main conclusions of the study are as follows:(1)Based on Zhu Wenquan’s improved CASA model,the distribution map of net primary productivity of vegetation in Linzhi region in 2008 was estimated.The order of net primary productivity(NPP)of each county from large to small is: Motuo County,Chayu County,Bomi County,Linzhi County,Milin County,Lang County,and Gongbujiangda County.(2)Based on the data from the 7th National Forest Resources Inventory and Fang Jingyun’s "Conversion Factor Continuous Function Method" for vegetation carbon sinks,the carbon reserves of forest ecosystems in various counties of Linzhi Prefecture in 2008 were quantitatively estimated.The forest carbon reserves in Linzhi Prefecture were approximately 219.03 million tons.The order of carbon reserves of forest ecosystems in various counties from large to small was as follows: Chayu County,Bomi County,Motuo County,Linzhi County,Milin County,Gongbujiangda County Langxian County.(3)Based on the USLE universal water and soil loss equation model,the quantitative estimation of soil erosion in Linzhi region was realized,and the water and soil conservation rate of each county in Linzhi region was measured.The research shows that the order of soil and water conservation rates in various counties in Linzhi region from high to low is: Motuo County,Bomi County,Chayu County,Linzhi County,Milin County,Lang County,and Gongbujiangda County.According to the classification of soil erosion levels,the distribution map of soil and water loss status in various counties in Linzhi region is obtained.(4)This study uses the PSR model to construct a forest ecological security evaluation system in Linzhi City based on 16 indicators.Among the five subsystems of forest structure,functional benefit,natural condition,pressure,and response,the weights from high to low are functional benefit(0.3419),natural condition(0.3045),forest structure(0.1558),pressure(0.1375),and response(0.0603),respectively,The internal differences in forest ecological security are mainly caused by the functional benefits of forest ecosystems and natural conditions.The top five specific indicators with the highest weight are:net primary productivity of vegetation(0.1267),altitude(0.1224),soil and water conservation rate(0.1015),annual average temperature(0.0781),and proportion of coniferous and broadleaved mixed forests(0.0725).Together,these five indicators explain 50.12% of the factors affecting forest ecological security.(5)According to the forest ecological security evaluation results calculated by the PSR model,the forest ecological security index of each county in Linzhi City is ranked from high to low as follows: Motuo County,Chayu County,Bomi County,Linzhi County,Gongbujiangda County,Milin County,and Lang County.In the evaluation and rating of forest ecological security,the "very safe" is Motuo County;Chayu County is in "critical safety";The "less safe" counties are Bomi County,Linzhi County,Gongbujiangda County,Milin County,and Lang County.