The carbon budget of California

The carbon budget of a region can be defined as the sum of annual fluxes of carbon dioxide (CO₂) and methane (CH₄) greenhouse gases (GHGs) into and out of the regional surface coverage area. According to the state government's recent inventory, California's carbon budget is presently dominated by 115 MMTCE per year in fossil fuel emissions of CO₂ (>85% of total annual GHG emissions) to meet energy and transportation requirements. Other notable (non-ecosystem) sources of carbon GHG emissions in 2004 were from cement- and lime-making industries (7%), livestock-based agriculture (5%), and waste treatment activities (2%). The NASA-CASA (Carnegie Ames Stanford Approach) simulation model based on satellite observations of monthly vegetation cover (including those from the Moderate Resolution Imaging Spectroradiometer, MODIS) was used to estimate net ecosystem fluxes and vegetation biomass production over the period 1990–2004. California's annual NPP for all ecosystems in the early 2000s (estimated by CASA at 120 MMTCE per year) was roughly equivalent to its annual fossil fuel emission rates for carbon. However, since natural ecosystems can accumulate only a small fraction of this annual NPP total in long-term storage pools, the net ecosystem sink flux for atmospheric carbon across the state was estimated at a maximum rate of about 24 MMTCE per year under favorable precipitation conditions. Under less favorable precipitation conditions, such as those experienced during the early 1990s, ecosystems statewide were estimated to have lost nearly 15 MMTCE per year to the atmosphere. Considering the large amounts of carbon estimated by CASA to be stored in forests, shrublands, and rangelands across the state, the importance of protection of the natural NPP capacity of California ecosystems cannot be overemphasized.     

Evaluating climate impacts on carbon balance of the terrestrial ecosystems in the Midwest of the United States with a process-based ecosystem model

The Midwest of the United States includes 12 states and accounts for about a quarter of the total United State land area. In recent years, there is an increasing interest in knowing the biomass potential and carbon balance over this region for the past and the future. In this study, we use the Terrestrial Ecosystem Model (TEM) to evaluate these quantities in the region from 1948 to 2099. We first parameterize the model with field data of major crops, including corn (Zea mays), soybean (Glycine max), and wheat (Triticum spp); then the model is applied to the region for the historical period (1948–2000). Next, we evaluate the simulated forestry biomass with forest inventory data, the agricultural net primary production (NPP) with agricultural statistics data, and the regional NPP with a satellite-based product at the regional scale. Our results show that the simulated annual NPP for the Midwest increased by 1.75% per year and the whole Midwest terrestrial ecosystem acted as a carbon sink during 1948–2005. During the 21st century, vegetation and soil carbon fluxes and pools show an increase trend with a great inter-annual variability. The ecosystems serve as a carbon sink under future climate scenarios. NPP in the Midwest will increase and net ecosystem production (NEP) will also increase and show an even larger interannual variability. This study provides the information of the biomass and NEP at a state- level in the Midwest, which will be valuable for the region stakeholders to better manage their land for the purpose of increasing carbon sequestration on the one hand and meeting the increasing demand of biomass on the other.     

Making carbon sequestration a paying proposition

Atmospheric carbon dioxide (CO₂) has increased from a preindustrial concentration of about 280 ppm to about 367 ppm at present. The increase has closely followed the increase in CO₂ emissions from the use of fossil fuels. Global warming caused by increasing amounts of greenhouse gases in the atmosphere is the major environmental challenge for the 21st century. Reducing worldwide emissions of CO₂ requires multiple mitigation pathways, including reductions in energy consumption, more efficient use of available energy, the application of renewable energy sources, and sequestration. Sequestration is a major tool for managing carbon emissions. In a majority of cases CO₂ is viewed as waste to be disposed; however, with advanced technology, carbon sequestration can become a value-added proposition. There are a number of potential opportunities that render sequestration economically viable. In this study, we review these most economically promising opportunities and pathways of carbon sequestration, including reforestation, best agricultural production, housing and furniture, enhanced oil recovery, coalbed methane (CBM), and CO₂ hydrates. Many of these terrestrial and geological sequestration opportunities are expected to provide a direct economic benefit over that obtained by merely reducing the atmospheric CO₂ loading. Sequestration opportunities in 11 states of the Southeast and South Central United States are discussed. Among the most promising methods for the region include reforestation and CBM. The annual forest carbon sink in this region is estimated to be 76 Tg C/year, which would amount to an expenditure of $11.1–13.9 billion/year. Best management practices could enhance carbon sequestration by 53.9 Tg C/year, accounting for 9.3% of current total annual regional greenhouse gas emission in the next 20 years. Annual carbon storage in housing, furniture, and other wood products in 1998 was estimated to be 13.9 Tg C in the region. Other sequestration options, including the direct injection of CO₂ in deep saline aquifers, mineralization, and biomineralization, are not expected to lead to direct economic gain. More detailed studies are needed for assessing the ultimate changes to the environment and the associated indirect cost savings for carbon sequestration.     

Net Carbon Exchange Across the Arctic Tundra-Boreal Forest Transition in Alaska 1981–2000

Shifts in the carbon balance of high-latitude ecosystems could result from differential responses of vegetation and soil processes to changing moisture and temperature regimes and to a lengthening of the growing season. Although shrub expansion and northward movement of treeline should increase carbon inputs, the effects of these vegetation changes on net carbon exchange have not been evaluated. We selected low shrub, tall shrub, and forest tundra sites near treeline in northwestern Alaska, representing the major structural transitions expected in response to warming. In these sites, we measured aboveground net primary production (ANPP) and vegetation and soil carbon and nitrogen pools, and used these data to parameterize the Terrestrial Ecosystem Model. We simulated the response of carbon balance components to air temperature and precipitation trends during 1981–2000. In areas experiencing warmer and dryer conditions, Net Primary Production (NPP) decreased and heterotrophic respiration (R _H ) increased, leading to a decrease in Net Ecosystem Production (NEP). In warmer and wetter conditions NPP increased, but the response was exceeded by an increase in R _H ; therefore, NEP also decreased. Lastly, in colder and wetter regions, the increase in NPP exceeded a small decline in R _H , leading to an increase in NEP. The net effect for the region was a slight gain in ecosystem carbon storage over the 20 year period. This research highlights the potential importance of spatial variability in ecosystem responses to climate change in assessing the response of carbon storage in northern Alaska over the last two decades.     

喀斯特常绿与落叶阔叶混交林过去50年来的碳循环模拟

通过对Forest-DNDC模型的植被和土壤参数本地化校准,以气象插值数据为输入,模拟了贵州省普定县高原型喀斯特次生常绿与落叶阔叶混交林1965~2014年的土壤、植被和生态系统碳循环特征。结果表明,与冷模拟和实测值相比,参数本地化校准后的模型能更准确地模拟春、秋、冬3个季节的土壤呼吸动态,而模拟的夏季土壤呼吸偏小;但统计检验指出,参数修订后的Forest-DNDC模型能够较好地模拟喀斯特森林土壤呼吸,降低了模拟误差,可用于喀斯特常绿与落叶阔叶混交林碳动态的模拟。进一步分析发现,1965~2014年喀斯特森林的碳通量除模拟早期的前3~4年急剧增加之外,随后总初级生产力(GPP)保持相对稳定,植物呼吸(Rplant)和生态系统呼吸(R_(ecosystem))随着森林发育而增加,土壤呼吸(R_(soil))减少,植被净初级生产力(NPP)呈迅速减小趋势;净生态系统碳交换量(NEE)亦较迅速下降,在2013年达到最低值-0.17 t C/ha,喀斯特森林由碳汇变为弱碳源。相关分析表明,年均温度和年降水对喀斯特常绿与落叶阔叶混交林的GPP和R_(soil)没有显著影响,但却显著影响NPP、R_(plant)、R_(ecosystem)和NEE。     

Estimation of carbon dioxide flux and source partitioning over Beijing, China

The magnitude and partitioning of carbon dioxide emission from the urban area in Beijing, China was estimated based on a statistical approach. Results showed that the urban surface is a net source of CO2 to atmosphere. The main sources of CO2 are vehicles, which accounted for 75.5% and 38.9% of CO2 emission in summer and winter, respectively. At midday in summer, the CO2 uptake of-0.034 mg/（m^2.sec） indicated that vegetation is an important sink of CO2 in summer. Comparison between the annual emission rates of CO2 from the statistical approach and that directly measured by the eddy covariance technique implies that a bottom-up emission approach is a viable means to estimate CO2 emission in an urban area.     

模拟大气 CO2水平升高对春季太湖浮游植物生理特性的影响

基于2012年春季在太湖梅梁湾进行为期27 d的不同CO2水平(大气CO2体积分数([CO2,g])梯度为270×10-6、380×10-6、750×10-6)的野外培养实验,揭示了大气CO2水平升高对太湖浮游植物的碳源选择、生长速率、光合作用、净初级生产力和细胞化学元素组成等生理过程的影响,结果表明,大气CO2浓度的升高首先会显著改变太湖水体的pH值和碳化学环境,减弱浮游植物碳浓缩机制(CCM)的必要性.大气CO2浓度加倍后,浮游植物的最大生长速率(Umax)、净初级生产力(NPP)、单位叶绿素a(Chl-a)含量的NPP会分别增加63.1%、69.6%、33.8%.大气CO2浓度的升高会促进太湖绿藻和硅藻的最大光合作用效率并且其对硅藻的促进作用比绿藻更显著,但并没有改变春季蓝藻光合作用活性极低的现状.大气CO2浓度的升高在提高浮游植物细胞中C、N含量的同时,却减少了P的吸收.本研究结果将为预测和揭示太湖浮游植物对未来气候变化的响应提供理论基础.     

山东黄河下游流域土壤碳储量及时空变化研究

全球气候变暖及其影响是当前人类面临的重大环境问题之一,大气CO2浓度的剧增为人类生活带来的诸多环境问题越来越严重。土壤有机碳是陆地生态系统碳库的重要组成部分,它的微小变化直接影响大气温室气体的浓度。本文利用2003~2010年多目标区域地球化学调查及20世纪80年代全省第二次土壤普查碳数据,对山东省黄河下游流域土壤碳密度、碳储量及时空变化规律和固碳潜力与机制进行了研究,结果表明,1.0 m土层有机碳库约占我国SOCP的3.28%;表现出"碳汇";水稻土碳密度最高、砂姜黑土次之,滨海盐土最低;研究区0~1.0 m土层固碳潜力为1.02×109t,相当于可减少大气中0.081%CO2浓度。通过相关性分析表明,在土壤中增施有机肥和N、P、K肥,以及施用Zn等矿质肥料可有效提高土壤中的有机碳量,提升土壤固碳能力,而含Cl量过高是滨海土壤固碳的破坏性因素。本研究为缓解大气CO2浓度的剧增的环境压力,发挥和提高我国土壤生态系统的固碳潜力提供了科学依据。     

气候变化背景下人类活动对承德接坝区植被净初级生产力的影响

承德接坝区位于农牧过渡区,对气候变化和人类活动极为敏感.以植被净初级生产力(NPP)作为评价指标,基于Thornthwaite Memorial模型计算潜在NPP和MODIS NPP遥感影像获取实际NPP数据,利用潜在NPP与实际NPP间的差值衡量人类活动作用下NPP的大小,运用Slope趋势和变异系数法分析实际NPP、潜在NPP和人类活动作用下NPP的变化趋势及稳定性分布,并采用相关系数法分析实际NPP与年降水量和年均气温间的相关性,最终量化气候变化和人类活动对该区域植被变化的影响.结果表明,潜在NPP自西北向东南递增,其变化趋势和稳定性均为自西向东递增.实际NPP与年降水量和年均气温呈正相关区域面积占比分别是99.87%和91.66%.该区域99.85%的植被得到改善且变化稳定,主要是由气候因素和人类活动共同主导(99.71%),而植被退化完全是由人为因素所导致(0.15%).     

粤港澳大湾区植被CUE变化及与气候变化的关系

基于MOD17数据,采用趋势分析和相关分析法,研究了2000~2019年粤港澳大湾区植被生产力和植被碳利用率（CUE）变化及其与气候变化的关系.结果表明,粤港澳大湾区总初级生产力（GPP）和净初级生产力（NPP）均值分别为1.80和0.89kg·C/m²,呈中部低四周高的空间格局,CUE均值为0.51,呈中部和东南部略高于四周的空间格局;GPP和NPP总体呈增加趋势,其年际变化率均值分别为0.01和0.001kg·C/（m²·a）,GPP年增长率远高于NPP年增长率,不同植被类型GPP和NPP也呈增加趋势.植被CUE则呈逐年下降趋势,其年际变化率均值为-0.002a^-1,由于气候因子变化对光合作用速率和呼吸作用速率产生的不同程度影响,从未来发展趋势看,68.22%的区域表明CUE仍呈下降趋势,植被碳固定能力减弱;不同植被类型CUE存在差异,其中农田CUE平均值最高,为（0.511±0.014）,森林和草地CUE分别为（0.500±0.019）和（0.501±0.020）,从变化趋势看,不同植被类型CUE呈极显著下降趋势（P < 0.01）;GPP与气温、累积降雨和累积净太阳辐射量总体呈正相关关系,其所占比例分别为94.52%、53.36%和90.58%,NPP与气温、累积降雨和累积净太阳辐射量总体上也表现为正相关关系,其所占比例分别为86.86%、71.10%和85.97%.然而,CUE与气候因子的关系却有所不同.CUE与气温和累积降雨呈正相关关系,但与累积太阳辐射呈负相关关系,不同植被类型GPP、NPP和CUE与气温、累积降雨量呈正相关关系,GPP和NPP与累计净太阳辐射呈正相关关系,但CUE与累积太阳辐射却呈负相关关系.     

中国农业植被净初级生产力模拟(I)——模型的建立与灵敏度分析

以业已建成的稻麦作物净初级生产力模型为基本框架,建立了一个具有普适性的中国农业植被净初级生产力模型(CropC-)。CropC-的模拟对象为占我国农作物总播种面积2/3的水稻、小麦、玉米、棉花、油菜和大豆。该模型包括2个主要功能模块:光合作用和呼吸作用;土壤-作物系统氮素运移。前者综合考虑了环境因子和氮素的影响,后者包括了作物氮素吸收、土壤氮矿化和化肥氮释放。灵敏度分析表明,在输入参数变化±10%时,CropC-对6个主要输入参数响应的敏感性依次为温度>光合有效辐射>大气CO2浓度>土壤全氮含量>施氮量>降水。模型分析表明,气候变暖将降低作物净初级生产力。     

中国农业植被净初级生产力模拟(I)——模型的建立与灵敏度分析

以业已建成的稻麦作物净初级生产力模型为基本框架,建立了一个具有普适性的中国农业植被净初级生产力模型(CropC-)。CropC-的模拟对象为占我国农作物总播种面积2/3的水稻、小麦、玉米、棉花、油菜和大豆。该模型包括2个主要功能模块:光合作用和呼吸作用;土壤-作物系统氮素运移。前者综合考虑了环境因子和氮素的影响,后者包括了作物氮素吸收、土壤氮矿化和化肥氮释放。灵敏度分析表明,在输入参数变化±10%时,CropC-对6个主要输入参数响应的敏感性依次为温度>光合有效辐射>大气CO2浓度>土壤全氮含量>施氮量>降水。模型分析表明,气候变暖将降低作物净初级生产力。     

青海湖东北岸天然草地CO2 通量变化特征

采用涡度相关法对青海湖东北岸地区草甸化草原生态系统的CO₂ 通量进行了观测,结果表明： 在生长季节(5~9 月),就日变化,08:00~19:00 为CO₂ 净吸收,20:00~07:00 为CO₂ 净排放,CO₂ 通量 净吸收峰值一般出现在12:00 时,7 月份12:00 时CO₂ 净吸收峰值为1.41 g·(m2·h)^-1;就月变化,7 月 是生长季CO₂ 净吸收最高月份,月CO₂ 净吸收量达到162.70 g·m^-2,整个生长季CO₂ 净吸收的总量达 468.07 g·m^-2。非生长季节(1~4 月及10~12 月),CO₂ 通量日变化振幅极小,最大CO₂ 净排放通量出现 在3 月,为0.29 g·(m2·h)^-1,除12 月和1 月各时段CO₂ 通量接近于零,其余月份各时段CO₂ 净排放在 0.02~0.29 g·(m2·h)^-1;3 月是全年CO₂ 净排放的最高月份,全月CO₂ 净排放量为72.33 g·m^-2,整个非生 长季CO₂ 净排放为319.78 g·m^-2。结果表明,无放牧条件下青海湖东北岸地区草甸化草原,全年CO₂ 净吸收量达148.30 g·m^-2,是显著的CO₂ 汇。     

基于IOCS的内蒙古潜在植被NPP空间分布特征研究

以综合顺序分类系统(IOCS)为基础,利用1985-2009年内蒙古及周边常规气象站的观测资料,采用NPP分类指数模型模拟内蒙古各潜在植被类型NPP,分析其空间分布特征及NPP与气候因子之间的关系。研究表明:①内蒙古地区植被NPP在空间分布上表现出一定的经向分布特征,多年均值介于0~366.5 gC·m^-2·a^-1之间,高值区中心分布在大兴安岭东北部;②各潜在植被类型中,碳汇潜力贡献率最大的潜在植被类型为微温微干温带典型草原类(ⅢC),其值为23.6%;最小的为寒温微干山地草原类(ⅡC),接近于0;③内蒙古潜在植被类型NPP表现出明显的干湿地带性和纬度地带性,且随寒温→微温→暖温、微干→微润→湿润→潮湿的变化其NPP值逐渐增大;但暖温极干暖温带荒漠类(ⅣA)和暖温干旱暖温带半荒漠类(ⅣB)并不符合这一规律,主要原因是较高的温度和较少的降水,达不到植被物质生长的需求。     

广东省土地覆盖变化对植被净初级生产力的影响分析

理解土地利用/覆盖变化对植被净初级生产力（Net Primary Productivity,NPP）的影响对于全球碳循环和粮食安全具有重要意义。论文采用优化的CASA（Carnegie-Ames-Stanford Approach）模型估算广东省2000、2005和2010年NPP,分析NPP的空间格局和土地覆盖的时空动态,研究土地覆盖变化对NPP的影响。结果表明：1）广东省NPP空间分布不均,形成一系列高值区和低值区;总体上是粤中区最高,珠三角区最低。2）2000—2010年广东省土地覆盖变化程度增强,城市用地和耕地变化最大,主要集中在珠三角区和粤中区。3）在气候变化条件下,以城市扩张为主导的广东省土地覆盖类型变化整体上造成NPP的损失,损失量主要来自林地和耕地向低生产力土地覆盖类型的转换,尤其是被城市用地占用;不同生态区NPP损失差异显著,珠三角区和粤中区NPP损失较为严重;2005—2010年珠三角区NPP损失量有所降低,其他生态区均有所增加,体现了城市扩张对NPP影响的复杂性。     

北京及其北部地区大气降尘时空分布特征

文章研究了北京及其北部邻近地区降尘量的时空分布特征和变化规律.在该区的10个采样点开展了为期一年的大气降尘收集工作,结果表明,研究区内年均降尘量为58.4g/(m2·a),最高和最低年降尘量分别位于研究区西北部的张北和东南部的滦平,其年均降尘量分别为169g/(m2·a)和15.6g/(m2·a).整个研究区的降尘主要...     

粤港澳大湾区吸收性气溶胶的解析

为了解粤港澳（Guangdong-Hong Kong-Macao,GHM）大湾区气溶胶污染现状,基于OMAERUV日产品数据,对粤港澳大湾区2008~2019年吸收性气溶胶指数（ultraviolet aerosol index,UVAI）的时空分布、未来趋势变化和潜在源区进行了分析,并对其影响因素进行了探讨.结果表明,GHM大湾区年时间序列上UVAI呈现出下降的趋势,年均下降为2.3%;月时间序列上从春季开始呈现倒"V"形,季节特征春季最高,冬、秋次之,夏季最低;空间上呈现中部区域一直属于高值区,12年年均UVAI高达0.35;UVAI分布在时间序列主要表现为可持续,有82.69%的区域在未来UVAI将呈现下降的趋势;GHM大湾区外部潜在源主要是东部工业产生的碳质源和海洋带来的生物源;UVAI潜在源区春季以碳质源和生物质源为主,夏季以生物质气溶胶源为主,秋季以碳质源占比最大,冬季沙尘性质气溶胶源有所增加;通过相关性分析,气溶胶和PM_2.5之间是相互依附的关系,工业生产活动是大气气溶胶的重要组成部分,降水可以降低大气中因工业生成所产生的气溶胶含量,第二产业活动在气温升高的情况下会加快气溶胶的生成.     

京津冀区域生产和消费CO2排放的时空特点分析

区分消费和生产二氧化碳排放是对开放的经济区域进行排放责任划分的基础,日渐受到政策制定者的关注.利用经济投入产出-生命周期分析模型,对京津冀区域1997年、2002年和2007年的消费和生产二氧化碳排放时空特征及二氧化碳排放平衡进行分析.结果表明,京津冀区域消费和生产二氧化碳排放呈约4%的年均增长;贸易隐含二氧化碳排放比例为30%~83%,并以国内贸易隐含二氧化碳排放为主;河北的消费和生产二氧化碳排放占区域主导,增速和二氧化碳排放强度高于北京和天津;京津冀区域为二氧化碳排放净流入区域,存在部分排放责任转移;京津为二氧化碳排放净转入地区,冀为二氧化碳排放净转出地区;京津冀三地二氧化碳排放关键部门分布集中且相似度较高,可以考虑区域联合控制.其中,电力、蒸汽、热水生产和供应业和金属冶炼及压延加工业对二氧化碳排放的依赖性最大,承担较大的其他部门的二氧化碳排放责任.投入产出分析解析了地区生产和消费二氧化碳排放情况,有利于区域减排的精细化管理和制定相应对策,并促进区域减排合作.     

红枫水库水-气界面二氧化碳分压及扩散通量的时空变化

红枫水库是我国西南喀斯特地区典型的人工湖泊,具有特殊的水文地质特征。准确估算其CO_2排放通量,对了解该水库碳循环具有重要意义。因此,于2017年7月至2018年4月采用走航式监测对库区(南湖和北湖)水气界面二氧化碳分压(pCO_2)和水质参数的时空变化进行了调查。结果表明,红枫水库pCO_2的分布具有明显的时空差异。库区秋、冬季表层水体pCO_2均超过大气pCO_2,表现为CO_2的净排放;春、夏季则相反,表现为CO_2的净吸收。从空间分布上来看,春、秋季北湖pCO_2要明显高于南湖,特别是秋季更为明显。另外,基于高频的走航监测数据,计算得到红枫水库全年CO_2的排放均值约为613mmol/(m~2·d)。     

Modeling harvest and biomass removal effects on the forest carbon balance of the Midwest,USA

The objective of this study was to use an ecosystem process model, Biome-BGC, to explore the effects of different harvest scenarios on major components of the carbon budget of 205,000 km² of temperate forest in the Upper Midwest region of the U.S. We simulated seven harvest scenarios varying the (i) amount of harvest residue retained, (ii) total harvest area, and (iii) harvest type (clear-cut and selective) to assess the potential impacts on net biome production (NBP), net primary production (NPP), and total vegetation carbon. NBP was positive (C sink) in year 1 (2004) and generally decreased over the 50-year simulation period. More intensive management scenarios, those with a high percentage of clear-cut or a doubling of harvest area, decreased average NBP by a maximum of 58% and vegetation C by a maximum of 29% compared to the current harvest regime (base scenario), while less intensive harvest scenarios (low clear-cut or low area harvested) increased NBP. Yearly mean NPP changed less than 3% under the different scenarios. Vegetation carbon increased in all scenarios by at least 12%, except the two most intensive harvest scenarios, where vegetation carbon decreased by more than 8%. Varying the amount of harvest residue retention had a more profound effect on NBP than on vegetation C. Removing additional residue resulted in greater NBP over the 50-year period compared to the base simulation. Results from the seven model simulations suggest that managing for carbon storage and carbon sequestration are not mutually exclusive in Midwest forests.