|Alternative Title||The influence of human activities on greenhouse gas budgets of forestry and agriculture in China|
|Thesis Advisor||王效科 ; 逯非|
|Place of Conferral||北京|
|Keyword||人类活动,森林生态系统,森林,农田,温室气体收支 Human Activities, Forest Ecosystem, Forestry, Agriculture, Greenhouse Gases Budget|
森林和农田生态系统作为陆地生态系统的重要组成部分，在减缓或者增加大气温室气体浓度中具有重要的作用。林业生产中的造林、营林、灾害控制和木材调减等管理活动，农业生产中的施肥和秸秆还田等措施都能够增加森林和农田生态系统的碳贮量。然而，管理措施中化石燃料等物资的使用也会造成温室气体的排放。在全面评估我国森林生态系统碳动态基础上，分析了人类活动对森林生态系统碳动态的整体影响，通过建立林业碳计量与净减排核算方法（Carbon Accounting and Net Mitigation of Forestry，CANM–Forestry）和农业碳计量与净减排核算方法（Carbon Accounting and Net Mitigation of Cropland，CANM–Cropland），分析了各项具体的管理措施对林业和农业生产过程中温室气体收支的影响，明确了减缓林业和农业碳排放的有效地管理措施。主要研究结果如下：
（1）1977-2013年我国森林植被碳贮量和碳密度分别增长了2729 Tg C和7.7 Mg C ha-1，这主要是由于造林和森林保护工程的引起的，其中森林面积扩张对植被碳贮量的增加的贡献达到60.0%。研究期间，44.2-54.6%的植被碳贮量分布在黑龙江、云南、内蒙古和四川四个省份；碳密度由人口稠密的东南地区向人口稀少的东北和西部地区增加。另外，人口密度与植被碳密度呈显著负相关关系，空间上植被碳密度随着人口密度的增加而显著降低。由于经济发展、造林和森林保护工程的实施，1998年之后人口密度增长导致森林植被碳密度降低的程度减少。
2000-2014年我国森林火灾、病虫鼠害和采伐造成的碳排放量为22.8 Tg Ce yr–1，碳排放抵消了14.4%的森林植被碳汇。采伐是造成我国森林生态系统植被碳排放的主要因素，而不同区域的主要因素不同。华北、东北、华东、中南和西南地区采伐是造成碳排放的主要因素。西北地区病虫鼠害是碳排放的主要因素。木材调减和病虫鼠害防治可以减缓3.1 Tg Ce yr–1的碳排放，提高了2.3%的植被碳汇。从全国来看病虫鼠害防治对碳汇的改善作用较大。从区域来看华北和东北地区木材调减对碳汇的改善作用较大；华东、中南、西南和西北病虫鼠害防治对碳汇的改善作用较大。病虫鼠害防治和木材调减是减缓我国森林生态系统植被碳排放的重要措施，并应在不同区域有针对性的进行实施。
（2）2000-2014年我国林业的温室气体排放为17.7 Tg Ce yr-1，温室气体排放抵消了8.5%森林植被碳汇和木材碳汇以及薪材替代碳减排量，导致林业净碳汇为189.8 Tg Ce yr-1。15年来我国林业的温室气体排放增长了12.8 Tg Ce，这主要是由造林引起的。森林资源利用是我国林业温室气体排放的主要原因，而不同区域的主要排放因素不同。西南和西北地区造林是温室气体排放的主要因素；华北、东北、华东和中南地区资源利用是温室气体排放的主要原因。降低木材产量、改善化石燃料生产和利用效率以及发展薪炭林是减缓我国林业温室气体排放的重要措施，并应在不同区域有针对性的进行实施。
（3）2000-2015年我国主要农作物生产温室气体排放量为133.3 Tg Ce yr-1。施肥是我国农作物生产温室气体排放的主要因素。16年来主要农作物生产净温室气体排放仅增加了1.9%。70.6%的净温室气体集中在南部。过去16年随着秸秆还田和氮肥施用的土壤固碳量提高，我国单位面积和单位产量净温室气体排放分别降低了9.7%和30.4%。区域上，东北和西北地区由于施肥因素、北部由于机械作业、南部由于稻田CH4排放，导致区域温室气体排放量增加了9.1%-65.0%。然而单位产量净温室气体排放降低了15.0%-47.0%。提高氮肥利用效率和扩大秸秆还田面积比例降低了25.3 Tg Ce yr-1温室气体排放，是减缓我国农业温室气体排放的重要措施，并应在不同区域结合其他措施共同实施。
As the dominant part of terrestrial ecosystems, forest and cropland ecosystems paly the important roles in mitigating or increasing the atmospheric greenhouse gases (GHGs). The management measures of afforestation, silviculture, disaster control, and wood production reduction and so on in forestry, and fertilization and straw return in agricultural production all could increase the carbon (C) stock of forest and cropland ecosystems. However, the materials such as the fossil fuel used in management activities release GHG during their production, transportation and application. The influence of human activities on the temporal dynamics and spatial distribution of forest biomass C were analyzed based on the estimation of the forest biomass C dynamics of forest ecosystem. And the impact of specific management measures on GHG budget of forestry and agricultural production were also calculated by constructing the CANM–Forestry and CANM–Cropland methodologies, and the potential mitigation strategies of forestry and agricultural management measures were also be addressed. The main results showed as follows.
(1) The forest biomass C stock and density increased by 2729 Tg C and 7.7 Mg C ha-1 from 1977 to 2013 in China mainly due to the expansion of forest area. And 44.2-54.6% of the forest biomass C was distributed in Heilongjiang, Yunnan, Inner Mongolia, and Sichuan four provinces, and the forest biomass C density increased from the densely populated southeastern provinces to the sparsely populated northeastern and western provinces. Furthermore, the forest biomass C density was significantly negatively with population density, and the forest biomass C density decrease with the increase in population density on the spatial scale. The degree of the dependence of the forest biomass C on population density has been declining science 1998 because of the economic development, afforestation and the implement of forest conservation program. Forest fire; diseases, pests, and rats (DPR); and harvesting released 22.8 Tg Ce yr–1 and this emission offset 14.4% of forest biomass C sink from 2000 to 2014 in China. Harvesting was a major contributor to the national C emissions, while the main driving factor of regional C emissions was varied. Harvesting contributed the most to C emissions in the north, northeast, east, south, and southwest, while DPR dominated C emissions in the northwest. Furthermore, Wood production reduction and DPR control significantly mitigated 3.1 Tg Ce yr–1 emissions and improved 2.3% of biomass C sink, which mainly improved by DPR control. Wood production reduction dominated the improved effects in the north and northeast, while DPR control improved the most biomass C sink in the east, south, southwest, and northwest, indicating that DPR control and wood production reduction represented important mitigation strategies and should be targeted implementation in different regions.
(2) The total GHG emissions from forestry averaged 17.7 Tg Ce yr–1 and offset 8.5% of the forest biomass and products C sink and GHG mitigation from substitution effects, which resulted in a net C sink of 189.8 Tg Ce yr–1 from 2000 to 2014. GHG emissions from forestry increased by 12.8 Tg Ce, which was mainly induced by increases in afforestation. Forest resource utilization was a major contributor to the national GHG emissions, whereas the key driving factors for regional GHG emissions varied. In the southwest and northwest, afforestation dominated the GHG emissions. In the north, northeast, east, and south, forest resource utilization was the major contributor to GHG emissions. As forest management, decreased wood production, improved fossil fuels or fossil fuel-related product utilization efficiency and forests developed for bioenergy are important mitigation strategies that could increase the forest C sink in China and should be targeted for implementation in various regions.
(3) GHG emissions from main crop production was 133.3 Tg Ce yr-1 during 2000 to 2015, and fertilization contributed the most to the total GHG emissions. The GHG emission only increased by 1.9% during the past 16 years, and 70.6% of the national GHG emission distributed in the south. Moreover, the per unit area and per unit product GHG emission decreased by 9.7% and 30.4% with the increase in straw return which result in the increase in soil C sequestration and the improvement in efficiency of fertilizer application in the past 16 years. At the regional scale, GHG emissions increased by 9.1% - 65.0% mainly because of emission increased in fertilization in the northeast and northwest, in machinery operation in the north, and in CH4 emission from rice paddies in the south, respectively. However, the per unit product GHG emission decreased by 15.0% - 47.0% with soil C sequestration increase resulting from fertilization and straw return. As agriculture management, improved N fertilizer use efficiency and increase in the proportion of the cropland on which straw was returned are important mitigation strategies that could decrease 25.3 Tg Ce yr-1 of the GHG emission in China and should be targeted for implementation in various regions and combined with others management practices.
Hence, improved the management measures of forest and cropland ecosystem, strengthened the measures that in favor of increased the C sequestration, such as afforestation, silviculture, disaster control, wood production reduction and forests developed for bioenergy in forestry; improved N fertilizer use efficiency and increase in the proportion of the cropland on which straw was returned in agricultural production, together with improved fossil fuels or fossil fuel-related product utilization efficiency are all important mitigation strategies for GHG emission in China.
|刘魏魏. 人类活动对我国森林和农田温室气体收支的影响[D]. 北京. 中国科学院生态环境研究中心,2018.|
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