增强陆地生态系统碳汇(简称陆地碳汇)是减缓大气二氧化碳(CO_(2))浓度上升和全球变暖的重要手段,也是实现我国“碳中和”目标的有效途径.为全面理解陆地碳汇特征及其对实现“碳中和”目标的贡献,本文系统梳理了近40年来陆地碳源汇研究...增强陆地生态系统碳汇(简称陆地碳汇)是减缓大气二氧化碳(CO_(2))浓度上升和全球变暖的重要手段,也是实现我国“碳中和”目标的有效途径.为全面理解陆地碳汇特征及其对实现“碳中和”目标的贡献,本文系统梳理了近40年来陆地碳源汇研究的主要进展,阐述了全球和我国陆地碳汇的时空格局及其驱动因素,分析了陆地碳汇对实现“碳中和”目标的作用.根据全球碳收支评估报告,过去60年全球陆地碳汇从1960年代的(-0.2±0.9)Pg C yr^(-1)(弱碳源;1 Pg=10^(15)g=10亿吨碳)增加至2010年代的(1.9±1.1)Pg C yr^(-1)(碳汇).目前,陆地碳汇主要分布在北半球中高纬度地区,而热带地区表现为微弱的碳汇或碳源.不同类型生态系统的碳汇大小存在差异:森林是陆地碳汇的主体,灌丛、湿地生态系统和农田土壤整体表现出碳汇功能,但草地的碳源汇功能尚不明确.此外,荒漠生态系统可能起着碳汇功能,但其大小和形成机制尚存在争议.大气CO_(2)浓度上升、氮沉降、气候变化和土地覆盖变化等是影响陆地碳汇强度的主要因素,火灾、气溶胶等因素也影响其大小.不同区域陆地碳汇的驱动因素存在差异:北美和欧洲陆地碳汇主要是大气CO_(2)浓度上升和气候变化等因素所致;而在中国,除了上述全球变化要素外,植树造林、生态修复也是驱动其碳汇的重要因素.综合以往研究结果评估,目前我国陆地碳汇强度为0.20~0.25 Pg C yr^(-1),预计2060年可能处于0.15~0.52 Pg C yr^(-1)之间.未来研究需通过扩大生态系统调查与监测的范围、完善陆地生物圈模型等途径提升陆地碳汇的评估精度,量化各类措施对生态系统碳汇潜力的影响,精准评估我国陆地碳汇对实现“碳中和”目标的贡献.展开更多
In recent decades, there have been a number of debates on climate warming and its driving forces. Based on an extensive literature review, we suggest that (1) climate warming occurs with great uncertainty in the magni...In recent decades, there have been a number of debates on climate warming and its driving forces. Based on an extensive literature review, we suggest that (1) climate warming occurs with great uncertainty in the magnitude of the temperature increase; (2) both human activities and natural forces contribute to climate change, but their relative contributions are difficult to quantify; and (3) the dominant role of the increase in the atmospheric concentration of greenhouse gases (including CO 2 ) in the global warming claimed by the Intergovernmental Panel on Climate Change (IPCC) is questioned by the scientific communities because of large uncertainties in the mechanisms of natural factors and anthropogenic activities and in the sources of the increased atmospheric CO 2 concentration. More efforts should be made in order to clarify these uncertainties.展开更多
A goal of a 50% reduction in global greenhouse gases emissions by 2050, with an 80% reduction by developed countries (hereafter referred to as the G8 Goal), was proposed at the G8 Summit held in L’Aquila, Italy, in J...A goal of a 50% reduction in global greenhouse gases emissions by 2050, with an 80% reduction by developed countries (hereafter referred to as the G8 Goal), was proposed at the G8 Summit held in L’Aquila, Italy, in July 2009. Here we analyze the scientific and political implications of the G8 Goal and its equity and feasibility by examining four greenhouse gas emissions scenarios. Our results show that (1) the goal to keep atmospheric CO2 concentration of <450 ppmv, stated by G8 nations, can only be achieved under the scenario of a steady, linear emissions reduction by all countries and simultaneously meeting the G8 Goal during the period 2005-2050; (2) under the G8 Goal, the carbon emissions quota for developing countries would not meet their carbon emission demands even if very strict reduction regimes are followed, with a gap of up to >1/3 of emissions demand in the next 45 years; and (3) under the G8 Goal, the cumulative per capita emissions during the period of 2006-2050 for developed and developing countries will be 81 t C and 40-47 t C, respectively, with the former doubling that of the latter, implying that the historical disparity of carbon emissions between developed and developing countries would be widened. Historically, the cumulative per capita emissions from developed countries are 12 times of those from developing countries. We therefore conclude that (1) the G8 Goal seeks to impose binding reduction targets on developing countries that will impede their industrialization process and cause conflicts among developing countries in the allocation of carbon emission rights; (2) the G8 Goal will not only widen the existing disparities of historical carbon emissions between developed and developing countries, but also generate new inequalities in the rights of carbon emissions; and (3) the 450 ppmv threshold of atmospheric CO2 concentration control, which is the basis for the G8 Goal, is impractical and impossible, and should not be accepted as the foundation for international climate negotiation on carbon emission reduction. In summary, the G8 Goal is clearly against the principle of "common but differentiated responsibilities" and thus is unacceptable for developing countries.展开更多
The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and...The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and mechanical properties could provide benefits for forestry management and bases for wood application and forest tree breeding. However, current studies on wood properties mainly focus on wood density and ignore other wood physical properties. In this study, we established a comprehensive database of wood physical properties across major tree species in China. Based on this database, we explored spatial patterns and driving factors of wood properties across major tree species in China. Our results showed that(i) compared with wood density, air-dried density, tangential shrinkage coefficient and resilience provide more accuracy and higher explanation power when used as the evaluation index of wood physical properties.(ii) Among life form, climatic and edaphic variables, life form is the dominant factor shaping spatial patterns of wood physical properties, climatic factors the next, and edaphic factors have the least effects, suggesting that the effects of climatic factors on spatial variations of wood properties are indirectly induced by their effects on species distribution.展开更多
文摘增强陆地生态系统碳汇(简称陆地碳汇)是减缓大气二氧化碳(CO_(2))浓度上升和全球变暖的重要手段,也是实现我国“碳中和”目标的有效途径.为全面理解陆地碳汇特征及其对实现“碳中和”目标的贡献,本文系统梳理了近40年来陆地碳源汇研究的主要进展,阐述了全球和我国陆地碳汇的时空格局及其驱动因素,分析了陆地碳汇对实现“碳中和”目标的作用.根据全球碳收支评估报告,过去60年全球陆地碳汇从1960年代的(-0.2±0.9)Pg C yr^(-1)(弱碳源;1 Pg=10^(15)g=10亿吨碳)增加至2010年代的(1.9±1.1)Pg C yr^(-1)(碳汇).目前,陆地碳汇主要分布在北半球中高纬度地区,而热带地区表现为微弱的碳汇或碳源.不同类型生态系统的碳汇大小存在差异:森林是陆地碳汇的主体,灌丛、湿地生态系统和农田土壤整体表现出碳汇功能,但草地的碳源汇功能尚不明确.此外,荒漠生态系统可能起着碳汇功能,但其大小和形成机制尚存在争议.大气CO_(2)浓度上升、氮沉降、气候变化和土地覆盖变化等是影响陆地碳汇强度的主要因素,火灾、气溶胶等因素也影响其大小.不同区域陆地碳汇的驱动因素存在差异:北美和欧洲陆地碳汇主要是大气CO_(2)浓度上升和气候变化等因素所致;而在中国,除了上述全球变化要素外,植树造林、生态修复也是驱动其碳汇的重要因素.综合以往研究结果评估,目前我国陆地碳汇强度为0.20~0.25 Pg C yr^(-1),预计2060年可能处于0.15~0.52 Pg C yr^(-1)之间.未来研究需通过扩大生态系统调查与监测的范围、完善陆地生物圈模型等途径提升陆地碳汇的评估精度,量化各类措施对生态系统碳汇潜力的影响,精准评估我国陆地碳汇对实现“碳中和”目标的贡献.
基金supported by the Academic Division of the Chinese Academy of Sciencesthe National Natural Science Foundation of China (Grant No. 31021001)the National Basic Research Program of China (Grant No. 2010CB950600)
文摘In recent decades, there have been a number of debates on climate warming and its driving forces. Based on an extensive literature review, we suggest that (1) climate warming occurs with great uncertainty in the magnitude of the temperature increase; (2) both human activities and natural forces contribute to climate change, but their relative contributions are difficult to quantify; and (3) the dominant role of the increase in the atmospheric concentration of greenhouse gases (including CO 2 ) in the global warming claimed by the Intergovernmental Panel on Climate Change (IPCC) is questioned by the scientific communities because of large uncertainties in the mechanisms of natural factors and anthropogenic activities and in the sources of the increased atmospheric CO 2 concentration. More efforts should be made in order to clarify these uncertainties.
基金Supported by the Academic Division of the Chinese Academy of Sciences and the National Natural Science Foundation (Grant No. 90711002)
文摘A goal of a 50% reduction in global greenhouse gases emissions by 2050, with an 80% reduction by developed countries (hereafter referred to as the G8 Goal), was proposed at the G8 Summit held in L’Aquila, Italy, in July 2009. Here we analyze the scientific and political implications of the G8 Goal and its equity and feasibility by examining four greenhouse gas emissions scenarios. Our results show that (1) the goal to keep atmospheric CO2 concentration of <450 ppmv, stated by G8 nations, can only be achieved under the scenario of a steady, linear emissions reduction by all countries and simultaneously meeting the G8 Goal during the period 2005-2050; (2) under the G8 Goal, the carbon emissions quota for developing countries would not meet their carbon emission demands even if very strict reduction regimes are followed, with a gap of up to >1/3 of emissions demand in the next 45 years; and (3) under the G8 Goal, the cumulative per capita emissions during the period of 2006-2050 for developed and developing countries will be 81 t C and 40-47 t C, respectively, with the former doubling that of the latter, implying that the historical disparity of carbon emissions between developed and developing countries would be widened. Historically, the cumulative per capita emissions from developed countries are 12 times of those from developing countries. We therefore conclude that (1) the G8 Goal seeks to impose binding reduction targets on developing countries that will impede their industrialization process and cause conflicts among developing countries in the allocation of carbon emission rights; (2) the G8 Goal will not only widen the existing disparities of historical carbon emissions between developed and developing countries, but also generate new inequalities in the rights of carbon emissions; and (3) the 450 ppmv threshold of atmospheric CO2 concentration control, which is the basis for the G8 Goal, is impractical and impossible, and should not be accepted as the foundation for international climate negotiation on carbon emission reduction. In summary, the G8 Goal is clearly against the principle of "common but differentiated responsibilities" and thus is unacceptable for developing countries.
基金supported by Creative Research Groups of National Natural Science Foundation of China(31321061)National Natural Science Foundation of China(30370419 and 31300450)
文摘The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and mechanical properties could provide benefits for forestry management and bases for wood application and forest tree breeding. However, current studies on wood properties mainly focus on wood density and ignore other wood physical properties. In this study, we established a comprehensive database of wood physical properties across major tree species in China. Based on this database, we explored spatial patterns and driving factors of wood properties across major tree species in China. Our results showed that(i) compared with wood density, air-dried density, tangential shrinkage coefficient and resilience provide more accuracy and higher explanation power when used as the evaluation index of wood physical properties.(ii) Among life form, climatic and edaphic variables, life form is the dominant factor shaping spatial patterns of wood physical properties, climatic factors the next, and edaphic factors have the least effects, suggesting that the effects of climatic factors on spatial variations of wood properties are indirectly induced by their effects on species distribution.