北京市森林碳汇能力评价

Evaluation of forest carbon sequestration capacity in Beijing

【目的】根据第8次园林绿化植物普查中森林资源二类调查数据,对北京市森林碳汇能力进行评估,为该市森林资源的科学管理提供理论依据。【方法】本研究采取森林蓄积量扩展法,计算北京市森林整体碳储量、碳密度及其变化,并采用造林成本法和碳税法对其碳储量经济价值进行评估。【结果】(1)北京市森林总碳储量为1934.59万t,碳密度为32.35 t/hm^(2),各区域中密云区、延庆区、顺义区的碳储量较大,占比分别为13.79%、12.73%和11.40%,而碳密度较大的为顺义区、大兴区、通州区;平原和山地的碳密度均表现为阔叶林>混交林>针叶林,且平原地区碳密度约是山地的3.3倍;山地和平原地区的碳储量均以阔叶树为主,且平原地区表现出更强的森林固碳能力;防护林是森林碳储量贡献的主体,其中水土保持林碳储量最多,为414.15万t,而碳密度最大为农田防护林(175.23 t/hm^(2));优势树种碳储量大小排列为:其他杨树>栎树>油松>其他阔叶树>侧柏>刺槐>桦树>华北落叶松>山杨,碳密度大小排列为:其他杨树>桦树>华北落叶松>山杨>油松>刺槐>栎树>其他阔叶树>侧柏;不同起源中碳储量和碳密度均表现为:人工林>飞播林>天然林;龄组中碳储量大小:中龄林>幼龄林>成熟林>近熟林>过熟林,碳密度的总体规律为随着龄级的增大而增大。(2)从第1次到第8次森林资源调查,森林碳储量和碳密度持续增长;林种中特种用途林增长率最高,碳密度最大;华北落叶松、山杨的碳储量先增加再减少,而刺槐、桦树呈现先减少后增加的趋势,其他树种都呈增加趋势,而油松、华北落叶松、山杨的碳密度先增后减,侧柏、柞树、桦树先减后增,刺槐、阔叶树持续减小,杨树持续增大;天然林和人工林都呈增长趋势。(3)依据造林成本法和碳税法的不同碳价格估算,北京市森林碳储量经济价值在54.14×10^(8)~232.15×10^(8)元之间,碳税法下的森林碳储量经济价值较高。两种计算方法下北京市各区域中密云区、延庆区、顺义区碳储量经济价值最大;在所有优势树种中,杨树的碳储量经济价值最高;龄组中,中龄林对北京市的贡献最大。【结论】北京市森林具有明显的固碳潜力,但整体碳汇相对较低,今后应注重森林结构的搭配,加强林地的抚育管理,增强北京市森林碳汇的功能,提高碳汇价值,激发林业经营活力。

[Objective]Based on the existing survey data from the 8th Landscape Plant Census of Forest Resources TypeⅡsurvey data,the forest carbon sink capacity of Beijing was assessed to provide a theoretical basis for the scientific management of forest resources in the city.[Method]In this study,we adopted the forest stock expansion method to calculate the overall carbon stock,carbon density and changes in Beijing’s forests,and use the afforestation cost method and carbon tax method to assess the economic value of their carbon stocks.[Result](1)The total carbon stock of the total forest in Beijing was 1934.59×10^(4)t,and the carbon density was 32.35 t/ha,among the regions,Miyun District,Yanqing District and Shunyi District had larger carbon stocks,accounting for 13.79%,12.73%and 11.40%,respectively,while those with higher carbon density were Shunyi District,Daxing District and Tongzhou District;the carbon density of both plains and mountains showed broadleaf forests>mixed forests>coniferous forests,and the carbon density of forests in plains was about 3.3 times higher than that in mountains;the carbon stocks in both mountains and plains were dominated by broadleaf trees;protection forests were the main contributors to the forest carbon stock.The carbon stock of protection forest was the main contributor to forest stock,among which soil and water conservation forest had the largest carbon stock of 414.15×10^(4)t,while the carbon density of farmland protection forest was the largest at 175.23 t/ha;the carbon stock of dominant species was ranked as follows:other Populus spp.>Quercus spp.>Pinus tabuliformis>broadleaf tree>Platycladus orientalis>Robinia pseudoacacia>Betula spp.>Larix principis-rupprechtii>Populus davidiana,the carbon density was ranked as follows:other Populus spp.>Betula spp.>Larix principis-rupprechtii>Populus davidiana>Pinus tabuliformis>Robinia pseudoacacia>Quercus spp.>broadleaf tree>Platycladus orientalis;the carbon stock and carbon density in different origins were:planted forests>flycasting forests>natural forests;the carbon stock size in age group:middle-aged forest>young forest>mature forest>near-mature forest>over-mature forest,and the overall pattern of carbon density increased with the increase of age class.(2)From the first to the eighth forest resource survey,forest carbon stock and carbon density continued to increase;among the forest species,special-purpose forest had the highest growth rate and the highest carbon density;carbon stock of larch and aspen increased and then decreased,while acacia and birch showed a trend of decreasing and then increasing,and all other tree species showed an increasing trend,while carbon density of oleander,larch and aspen increased and then decreased,side cypress,Quercus spp.and birch decreased and then increased,acacia and broadleaf tree continued to decrease,and poplar continued to increase;both natural and planted forests showed an increasing trend.(3)Based on different carbon prices estimated by the afforestation cost method and the carbon tax method,the economic value of forest carbon stocks in Beijing ranged from 5.414 billion to 23.215 billion RMB,and the economic value of forest carbon stocks under the carbon tax method was higher.The economic value of carbon stock in each region of Beijing under the two calculation methods varied greatly,with Miyun,Yanqing,and Shunyi districts having the largest economic value of carbon stock;among all dominant tree species,poplar had the highest economic value of carbon stock;and among age groups,middle-aged forests had the largest contribution to Beijing.[Conclusion]Beijing’s forests have obvious carbon sequestration potential,but the overall carbon sink is relatively low.In the future,we should pay attention to the matching of forest structure,strengthen the management of forest land cultivation,enhance the function of Beijing’s forest carbon sink,improve the value of carbon sink,and stimulate the vitality of forestry management.