基于DNDC模型的双季稻体系氨挥发损失研究

为了探索长江流域双季稻体系氮肥施用对氨挥发损失的影响，评价Denitrification Decomposition (DNDC)模型对产量和氨挥发拟合的适应性，设计了早稻和晚稻不同氮肥用量田间试验，采用密闭室间歇通气法原位观测氨挥发排放通量，利用DNDC模型进行模拟分析，并运用模拟结果探讨了水稻产量和氨挥发损失与施氮量之间的关系。结果显示，模型能较好模拟双季稻体系水稻产量和氨挥发，早稻、晚稻和双季稻产量模拟值与观测值的相关系数分别为0.994、0.928、0.979，早稻、晚稻和整个双季稻生育期氨挥发模拟值与观测值的相关系数分别为0.994、0.998和0.997，均达到极显著水平。DNDC模型能较好预测因施肥引起的氨挥发排放峰，但在氨挥发通量和排放总量的定量上还需要进一步改进。敏感性指数分析表明，气温是影响作物产量的关键因素，氮肥用量和气温是影响氨挥发的主要因素。DNDC模型在模拟双季稻体系籽粒产量上具有较高的可信度，DNDC模拟和田间观测数据计算的最高产量施氮量分别是420和417 kg·hm^-2。稻田氨挥发损失量与施氮量之间满足二次函数和线性关系，二次函数能更好描述两者之间的关系。为使DNDC更准确的进行估算和应用，有必要获取更翔实的环境资料以减少输入数据的不确定性。     

不同麦秸还田方式对周年稻麦轮作农田碳足迹的影响

为明确麦秸不同还田方式对稻麦轮作农田碳足迹的影响，该研究通过开展两年的大田试验，设计了3种麦秸还田方式（麦秸旋耕还田、麦秸翻耕还田和麦秸沟埋还田），并以麦秸不还田为对照，采用静态箱-气相色谱法连续两年对农田温室气体排放进行监测，并对不同麦秸还田方式的生产资料投入和生产过程碳排放及温室气体排放进行全面分析。结果表明：(1）与不还田相比，麦秸还田显著增加了稻季日均CH4排放，稻麦周年全球增温潜势95%来自稻田CH4排放；（2）在水稻季，农田CH4排放占碳足迹总量比例最大，3种麦秸还田方式中，麦秸沟埋还田处理下碳足迹最小，且能比麦秸旋耕还田处理减少4.9%；(3）在小麦季，化肥投入造成的碳足迹所占比例最大，为64.5%~77.4%，其次是土壤N2O的排放；（4）从整个稻麦周年轮作系统来看，与麦秸旋耕还田和麦秸翻耕还田处理相比，麦秸沟埋还田处理能分别减少4.6%和3.6%的周年碳足迹及8.7%和4.9%的周年单位产量的碳足迹。因此，对于稻麦轮作地区，采用麦秸沟埋还田能在一定程度上降低农业生产过程中的碳足迹。     

中国海洋捕捞渔业温室气体排放时序分析与因素分解

综合渔获量规模、作业方式结构、作业方式能耗强度和燃油排放系数等因素对温室气体排放的影响，在对2006～2011年海洋捕捞渔业温室气体排放核算和时序分析基础上，利用LMDI方法对温室气体排放进行了因素分解。结果表明：海洋捕捞渔业温室气体排放量呈现出稳定的增长趋势，平均每年温室气体排放量增长2666万t；拖网、刺网两种作业方式产生的温室气体占相应年份海洋捕捞渔业温室气体排放量的比重最大，约占80%，且温室效应最强。渔获量规模效应是驱动我国海洋捕捞渔业温室气体排放的最主要因素。建议通过采取“捕捞配额”或实施较长期的禁渔休渔制度来降低渔获量总量，不仅有利于保护海洋渔业资源，还能减少温室气体排放，也可以通过建立海洋捕捞生态补偿制度的方式来调整作业方式结构向低温室气体排放转变     

农田温室气体净排放研究进展

农业是温室气体排放的主要排放源之一,农业温室气体减排对全球温室气体排放具有重要贡献,研究农田温室气体净排放潜力亦具有重要现实意义.本文阐述了农田温室气体净排放的涵义,并归纳总结了耕作方式、施肥、水分管理、间套作等农业措施对农田土壤有机碳(SOC)含量、农田土壤N2O和CH4、农田生产物资的使用所造成的温室气体(主要为CO2、N2O和CH4)排放的影响,结果表明:保护性耕作总体能提高表层SOC含量,减少CH4排放,但减少农田土壤N2O排放的研究尚存在一定的争议,耕作方式亦影响投入,从而影响温室气体的排放；施肥(特别是配施)能提高SOC含量.施氮肥越多,N2O排放量越大,而CH4主要受有机物料的影响较大；水分对减少N2O和CH4排放有相反作用,需综合进行平衡管理；不同的作物品种、间套作模式或促进或减少温室气体排放.此外,本文指出了国外在该领域的研究注重从系统角度考虑农田温室气体排放,而国内的研究则非常少,提出我国农田温室气体净排放可作为未来研究的一个重点,并对未来研究内容进行了初步归纳总结.     

华北集约高产农田温室气体净排放研究初探

本文以华北高产粮区山东桓台冬小麦-夏玉米轮作模式为例,借鉴LCA模型,初步探讨了华北平原通过长期大规模秸秆还田后温室气体排放的汇源问题。结果表明:综合考虑农资系统和农作系统,该模式表现为源,每各生产1 t冬小麦-夏玉米净温室气体排放量为-1 075.71kgCO2e;但具体到农作生产系统,轮作模式下农田生态系统固碳均值为+262.31 kgCO2e,能够抵消因施肥造成的-222.99 kgCO2e排放,并部分抵消机械燃油燃烧排放。因此,农作系统在坚持秸秆还田基础上,进一步改进耕作措施,具有成为温室气体排放汇的可能性。     

生物质炭及过氧化钙对旱地红壤CH4、CO2和N2O排放的影响

采用室内培养实验,在旱地红壤中添加生物质炭和过氧化钙,探究生物质炭和过氧化钙对旱地红壤CH_4、CO_2和N_2O排放及微生物活性的影响。本试验共设置4个处理,即CK(对照)、Ca(过氧化钙,1.72 g·kg~(-1))、C(生物质炭,21.46 g·kg~(-1))、C+Ca(生物质炭,21.46 g·kg~(-1);过氧化钙,1.72 g·kg~(-1))。结果表明:生物质炭和过氧化钙单施能够减少CO_2和N_2O通量,配施(C+Ca)对CH_4、CO_2和N_2O气体减排的效果更显著;从温室气体增温潜势(GWP)变化可以看出改良剂对温室效应具有明显的减轻作用。生物质炭和过氧化钙在一定程度上增加土壤pH、土壤微生物量碳和可溶性有机碳含量。土壤中添加生物质炭和过氧化钙均可以提高蔗糖酶、淀粉酶以及脲酶活性,其中配施(C+Ca)效果最好。因此,生物质炭和过氧化钙配施能够有效降低旱地红壤温室气体的排放量,对旱地红壤的减排可以起到一定作用。     

湖南省碳源与碳汇变化的时序分析

在全球气候变暖的背景下，减少温室气体排放、发展低碳经济成为各地区在发展中的普遍共识。以湖南省为研究区域，以1995~2008年为研究时序，从能源消费、主要工业产品生产工艺过程、土地利用变化与牲畜管理、固体废弃物处理与废水处理和排放4个方面综合分析了碳源与碳汇的变化情况。研究表明:1995~2008年，湖南省温室气体排放总量约在220亿t（2000年）至399亿t（2008年）CO2当量之间，14 a间增长了6118%，年均增长374%；碳汇总量约在1754亿t（1995年）至2537亿t（2007年）CO2当量之间，14 a间增长了3607%，年均增长约240%；能源消费与农业部门是湖南省温室气体的主要来源，林地是湖南省碳汇的主要来源；综合碳源与碳汇变化的均衡结果，1995~2008年湖南省呈碳汇盈余状态，净碳汇在2001~2007年持续增加，14 a间增长了31.94%，年均增长2.15%     

太湖流域上游外源氮、磷入湖通量模拟初步研究

湖泊-流域构成的复杂系统是湖泊富营养化研究的热点。应用SWAT模型对长江下游太湖流域上游外源氮、磷入湖通量进行模拟，以反映陆源入湖氮、磷营养盐的通量、空间分布和时间变化情况。以水文模拟为基础，引入相关系数（R）和Nash Sutcliffe效益系数（Ens）评价模拟结果。水文模拟率定期月均值R多在85%以上，Ens在024~090，模拟年平均径流量相对误差为32%。验证期各站月均值R均在80%以上，模拟年总量误差为81%。模拟结果显示，流域多年平均径流量为10415×108m3，营养盐输出浓度浙西区TN、TP分别为238 mg/L、018 mg/L；湖西区分别为568 mg/L、043 mg/L；武虞锡澄区分别为614 mg/L、040 mg/L。流域营养盐多年平均入湖通量TN为42 730 t/a，TP为3 075 t/a，2000年开始，流域TN、TP的入湖通量均有下降趋势。流域营养盐具显著空间差异，陈东港-大浦口、小梅口-长兜港、武进港-直湖港是最主要的入湖通道，贡献率分别达到27%、24%和20%，应作为流域外源营养物质管理和控制的重要区域     

崇明县农业温室气体排放核算

对崇明县农业2005～2009年所排放的CO2、CH4和N2O的量进行了核算，核算结果显示2005～2009年崇明县农业温室气体总量（折算为CO2）由1 038 527 t上升到1 076 993 t，上升比例为37%。其中，CO2和CH4的排放量分别从2005年的460 178 t和12 039 t下降到2009年的441 705 t和11 686 t，下降比例分别为40%和29%，但N2O的排放量则由2005年的1 050 t上升到2009年的1 258 t，上升比例为198%。N2O排放的快速增长和其巨大的增温潜力是影响崇明温室气体排放总量变化趋势的重要因素。核算结果表明，影响崇明农业温室气体排放的主要因素包括化肥使用强度过大和使用效率过低、粪便管理系统效率不高、农产品销售网络不完善等。未来崇明农业应主要从提高可再生能源利用比例和能源利用效率、实施精确施肥以降低化肥使用强度、提高畜禽粪便资源化利用率以及改善剩余农产品销售网络等方面来减少温室气体排放，从而实现可持续的低碳农业     

重庆市温室气体排放系统动力学研究

在全球气候变暖和快速城市化的背景下,开展城市温室气体减排研究十分迫切。重庆作为中国五大中心城市之一和西部唯一的直辖市,其协调经济发展和节能减排的实现模式对广大西部地区具有重要示范意义。本研究从社会经济发展的内部结构出发,以经济和人口增长导致的能源消费为核心,构建重庆市温室气体排放的系统动力学模型。研究中考虑不同投资率下的高、中、低三种经济发展模式,并在此基础上设置节能和低碳情景,探求节能水平提高、能源结构改善和碳汇能力增强对未来重庆温室气体排放的影响。模拟结果表明,产业能耗水平降低即节能情景,是重庆市温室气体减排的主要途径,对保证2020年中国单位GDP二氧化碳排放比2005年下降40%-45%目标的实现具有一定借鉴意义。最后本文在产业结构、能源消费、碳汇增加等方面针对重庆未来低碳经济发展提出对策建议。     

Mitigating GHG Emissions in the Humid Tropics: Case Studies from the Alternatives to Slash-and-Burn Program (ASB)

Tropical forest conversion contributes as much as 25% of the net annual CO₂ emissions and up to 10% of the N_2O emissions to the atmosphere. The net effect on global warming potential (GWP) also depends on the net fluxes of greenhouse gases from land-use systems following deforestation. Efforts to mitigate these effects must take into account not only the greenhouse gas fluxes of alternative land-use systems but also the social and economic consequences that influence their widespread adoption. The global alternatives to slash-and-burn program (ASB) investigated the net greenhouse gas emissions and profitability of a range of land-use alternatives in the humid tropics. The analysis showed that many tree-based systems reduced net GWP compared to annual cropping and pasture systems. Some of these systems are also profitable in terms of returns to land and labor. The widespread adoption of these systems, however, can be limited by start-up costs, credit limitations, and number of years to positive cash flow, in addition to the higher labor requirements. Projects that offset carbon emissions through carbon sinks in land use in the tropics might be a means of overcoming these limitations. A synthesis of the findings from this program can provide guidelines for the selection and promotion of land-use practices that minimize net global warming effects of slash-and-burn.     

Eco-balance analysis of land use combinations to minimize environmental impacts and maximize farm income in northern Japan

Relationships among global warming potential (GWP), farmland surplus nitrogen (FSN) and income for major land uses in the Ikushunbetsu watershed were compared using the eco-balance method. An empirical model was created for carbon dioxide, methane and nitrous oxide for both uplands and paddy rice using monitoring data from 22 fields. The greenhouse gas emissions were converted into GWP, whereas yield and FSN were obtained from interviews with farmers and a literature survey. Land use distribution was obtained by ground surveys in 2002, 2005 and 2007. The analysis showed that paddy rice and soybeans were characterized by a high GWP, low FSN and high income, whereas onions and vegetables had a high FSN but low GWP and moderate income. Wheat showed a negative GWP in some years, and abandoned areas always exhibited negative values. The total GWPs for the region were 14,184, 11,085 and 8,337 Mg CO₂ year⁻¹ for 2002, 2005 and 2007, respectively. The contribution of paddy rice to GWP was highest, ranging from 40 to 75%. To find optimal land use combinations that provide higher incomes and lower GWPs and FSNs than at present, all possible land use combinations were analyzed by changing the land use proportion from 0 to 100% at an interval of 10%. The number of land use combinations meeting the requirements in the three investigated years was 205. Abandoned area, which had the smallest environmental load, was included in every land use combination, indicating that land uses with low environmental impacts should be maintained at a certain proportion to mitigate the environmental load accompanying land uses with high production.     

江苏省交通运输业能源消费碳排放及脱钩效应

通过自上而下的计算方法，测算了江苏省1995～2010年交通运输行业能源消费碳排放量和人均碳排放量，并结合行业自身发展特点，扩展了Kaya恒等式，运用LMDI分解法进行分解分析。同时，在上述基础上采用Tapio模型对江苏省交通碳排放与交通运输业经济发展的脱钩关系进行了探讨。研究发现:(1)江苏省交通碳排放量与人均碳排量均呈明显上升趋势，其中石油制品类能源消费碳排放表现突出;(2)正向驱动交通碳排放量增加的因素为经济产出、人口规模和产业结构，负向驱动因素为交通能源结构和交通能源强度。其中，拉动碳排放量增长的决定性因素是经济产出规模的扩大，而促使碳排放减少的主要因素是交通能源强度的降低，相对于正向驱动因素，负向驱动因素抑制交通碳排放增加作用有限;(3)交通碳排放量变化与运输业经济发展之间的脱钩状态以扩张负连接、扩张负脱钩和弱脱钩为主，脱钩关系总体呈先恶化后改善的趋势，但要完全实现两者的绝对脱钩，依然任重道远     

Certainty and uncertainty in understanding global warming

Global warming has greatly concerned the whole world. Owing to the limitation we currently have, it is still difficult to completely understand the mechanism and physical science of climate change. Now both certainty and uncertainty coexist in the understanding of climate warming. This paper aims to summarize certainties and uncertainties in climate-warming studies, which focus on seven key problems related to human activities, namely, global warming, atmospheric concentrations of greenhouse gases, relationship between greenhouse gas emissions and climate warming, climate models, future climate change, 2°C warming threshold and tipping point in the Earth’s system. We should comprehensively take into account the level of certainty and uncertainty in our understanding of climate change while adapting to and mitigating global warming and adjusting our industrial structures accordingly. This would allow us to respond to change with certainty, while avoiding the risks associated with uncertainty.     

Certainty and uncertainty in understanding global warming

Global warming has greatly concerned the whole world.Owing to the limitation we currently have,it is still difficult to completely understand the mechanism and physical science of climate change.Now both certainty and uncertainty coexist in the understanding of climate warming.This paper aims to summarize certainties and uncertainties in climate-warming studies,which focus on seven key problems related to human activities,namely,global warming,atmospheric concentrations of greenhouse gases,relationship between greenhouse gas emissions and climate warming,climate models,future climate change,2?warming threshold and tipping point in the Earth's system.We should comprehensively take into account the level of certainty and uncertainty in our understanding of climate change while adapting to and mitigating global warming and adjusting our industrial structures accordingly.This would allow us to respond to change with certainty,while avoiding the risks associated with uncertainty.     

应对气候变化的碳足迹研究综述

由温室气体引起的全球变暖问题已引起国际社会的普遍关注,随着全球变暖成为社会关注的热点,碳足迹成为一个新的研究方法并迅速得到学术界的认可。本文从碳足迹的起源和各种定义入手,系统阐述了碳足迹的概念,并从不同角度探讨了碳足迹的各种分类。本文重点介绍了碳足迹的计算方法,主要包括投入产出分析方法、生命周期评价法、IPCC计算方法和碳足迹计算器等四大类,并总结和比较了四种方法的优缺点。在此基础上,对国内外相关研究系统地进行了归纳和总结,客观分析和评价了当前碳足迹的研究现状和存在的问题。本文还介绍了目前国际上四个主要的碳足迹评估标准:英国的PAS2050:2008标准、世界可持续发展商业协会和世界资源研究院共同发起制定的GHG议定书、日本的标准仕样书TS Q0010标准和ISO14067标准,并以GHG议定书和PAS2050两个标准为例分析了进行碳足迹评估的重要前提———边界界定问题。最后对碳足迹研究的重点领域和发展方向进行了展望。     

Methane and Nitrogen Oxide Fluxes in Tropical Agricultural Soils: Sources, Sinks and Mechanisms

Tropical soils are important sources and sinks of atmospheric methane (CH₄) and major sources of oxides of nitrogen gases, nitrous oxide (NM_2O) and NO_x (NO+NO₂). These gases are present in the atmosphere in trace amounts and are important to atmospheric chemistry and earth's radiative balance. Although nitric oxide (NO) does not directly contribute to the greenhouse effect by absorbing infrared radiation, it contributes to climate forcing through its role in photochemistry of hydroxyl radicals and ozone (O₃) and plays a key role in air quality issues. Agricultural soils are a primary source of anthropogenic trace gas emissions, and the tropics and subtropics contribute greatly, particularly since 51% of world soils are in these climate zones. The soil microbial processes responsible for the production and consumption of CH₄ and production of N-oxides are the same in all parts of the globe, regardless of climate. Because of the ubiquitous nature of the basic enzymatic processes in the soil, the biological processes responsible for the production of NO, N_2O and CH₄, nitrification/denitrification and methanogenesis/methanotropy are discussed in general terms. Soil water content and nutrient availability are key controls for production, consumption and emission of these gases. Intensive studies of CH₄ exchange in rice production systems made during the past decade reveal new insight. At the same time, there have been relatively few measurements of CH₄, N_2O or NO_x fluxes in upland tropical crop production systems. There are even fewer studies in which simultaneous measurements of these gases are reported. Such measurements are necessary for determining total greenhouse gas emission budgets. While intensive agricultural systems are important global sources of N₂O and CH₄ recent studies are revealing that the impact of tropical land use change on trace gas emissions is not as great as first reports suggested. It is becoming apparent that although conversion of forests to grazing lands initially induces higher N-oxide emissions than observed from the primary forest, within a few years emissions of NO and N₂O generally fall below those from the primary forest. On the other hand, CH₄ oxidation is typically greatly reduced and grazing lands may even become net sources in situations where soil compaction from cattle traffic limits gas diffusion. Establishment of tree-based systems following slash-and-burn agriculture enhances N₂O and NO emissions during and immediately following burning. These emissions soon decline to rates similar to those observed in secondary forest while CH₄ consumption rates are slightly reduced. Conversion to intensive cropping systems, on the other hand, results in significant increases in N₂O emissions, a loss of the CH₄ sink, and a substantial increase in the global warming potential compared to the forest and tree-based systems. The increasing intensification of crop production in the tropics, in which N fertilization must increase for many crops to sustain production, will most certainly increase N-oxide emissions. The increase, however, may be on the same order as that expected in temperate crop production, thus smaller than some have predicted. In addition, increased attention to management of fertilizer and water may reduce trace gas emissions and simultaneously increase fertilizer use efficiency.     

Mitigating Greenhouse Gas Emissions from Rice-Wheat Cropping Systems in Asia

The rice-wheat belt comprises nearly 24–27 million ha in South and East Asia. Rice is generally grown in flooded fields whereas the ensuing wheat crop requires well-drained soil conditions. Consequently, both crops differ markedly in nature and intensity of greenhouse gas (GHG) fluxes, namely emission of (1) methane (CH₄) and (2) nitrous oxide (N_2O) as well as the sequestration of (3) carbon dioxide. Wetland rice emits large quantities of CH₄; strategies to CH₄ emissions include proper management of organic inputs, temporary (mid-season) field drainage and direct seeding. As for the wheat crop, the major GHG is N_2O that is emitted in short-term pulses after fertilization, heavy rainfall and irrigation events. However, N_2O is also emitted in larger quantities during fallow periods and during the rice crop as long as episodic irrigation or rainfall result in aerobic-anaerobic cycles. Wetland rice ensures a relatively high content of soil organic matter in the rice-wheat system as compared to permanent upland conditions. In terms of global warming potential, baseline emissions of the rice-wheat system primarily depend on the management practices during the rice crop while emissions from the wheat crop remain less sensitive to different management practices. The antagonism between CH₄ and N_2O emissions is a major impediment for devising effective mitigation strategies in rice-wheat system - measures to reduce the emission of one GHG often intensify the emission of the other GHG.     

Integrated and comprehensive estimation of greenhouse gas emissions from land systems

Exchanges of carbon and nitrogen between the atmosphere and terrestrial ecosystems involve a complex set of interactions affected by both natural and management processes. Understanding these processes is important for managing ecosystem productivity and sustainability. Management processes also affect the net outcome of exchanges of greenhouse gases between terrestrial ecosystems and the atmosphere. In developing a national carbon accounting system (NCAS) for Australia to account for emissions and removal of greenhouse gases to and from the atmosphere, a carbon:nitrogen mass balance ecosystem model (FullCAM) was developed. The FullCAM model is a hybrid of empirical and process modelling. The approach enables application to a wide range of natural resource management issues, because it is at land-management-relevant spatial and temporal resolution and captures the main process and management drivers. The scenario-prediction capability can be used to determine the emissions consequences of different management activities. Because, in Australia, emissions of greenhouse gases are closely related to the retention of dead organic matter and the availability of nitrogen for plant growth, the carbon and nitrogen cycling as modelled are good indicators of ecosystem productivity and condition. The NCAS also emphasizes the advantages of a comprehensive and integrated approach to developing a continental scale ecosystem-modelling system that has relevance both to estimation of greenhouse gas emissions and sustainable management of natural resources.