太行山丘陵区群落演替进程中碳贮量变化特征

为了解植被演替过程中碳贮量分布格局,以太行山丘陵区典型群落为研究对象,采用样地调查法,对其生态系统碳贮量进行了研究.结果表明:(1)土壤碳密度随演替进程逐渐提高,其排序为:乔木阶段(58.3 t/hm2)＞灌丛阶段(43.1 t/hm2)＞草本阶段(20.47 t/hm2);(2)土壤活性有机碳含量随演替进程呈逐渐增高的趋势.其含量排序为:乔木阶段(0.94%)＞灌丛阶段(0.84%)＞草本阶段(0.34%);(3)在群落演替的过程中,植被碳贮量逐渐增加,栓皮栎群落最高,达40.30 t/hm2;草本群落阶段最低(1.34 t/hm2);灌木群落居中(8.26 t/hm2).在碳贮量构成中,乔、灌群落的乔木层碳贮量所占比重最高;草本层所占比例最小.草本层碳贮量所占比例随演替进程呈下降趋势.(4)生态系统碳总贮量随演替进程呈上升态势.由草本阶段的21.81 t/hm2,增加到灌木阶段的51.36 t/hm2,乔木群落阶段达到最大,为92.63 t/hm2.生态系统碳贮量增加约4.3倍.在碳贮量构成中,土壤碳储量所占比重最大.土壤碳贮量占总贮量的比重随演替进程呈下降趋势.     

洞庭湖湿地植被系统的碳贮量及其分配

利用生物量调查和实验数据.对洞庭湖湿地植被生态系统的碳密度、碳贮量及其分配进行研究.结果表明:乔木层植被碳密度为15.607～40.501 t/hm~2,草本层植被为5.906～21.632 t/hm~2.水生植物植被1.460～3.492 t/hm~2,平均14.954 t/hm~2比温带地区湿地植物碳密度高;未受干扰草甸土壤碳密度为260.510 t/hm~2,每年收获产品草甸是185.492 t/hm~2,林地234.513 t/hm~2,水生植物土壤为206.882 t/hm~2,低于全国湿地土壤平均值.碳贮量分配中.植被层、凋落物层和土壤层的碳贮量分别占各植被类型系统碳的总贮量的0.47%～14.69%,0.29%～1.10%和84.54%～99.53%.每年收获部分产品的草甸土壤碳密度只有未受人为干扰草甸的71.2%,原生草本植物草地改造成林地后,6年的时间,土壤的碳密度减少了10%.因此,控制人为干扰,防止湿地破碎化、保护好湿地、保证湿地的固碳潜力,是湿地管理中应该优先考虑的问题.     

不同坡位杉木林土壤碳储量研究

通过实地调查取样和室内实验测定,比较了上坡和下坡杉木的土壤碳库及其垂直分布差异,研究了坡位对杉木人工林固碳功能的影响。结果表明,杉木上坡和下坡的枯枝落叶层有机碳贮量分别为0.9和1.1t/hm2,坡下的枯枝落叶层有机碳贮量较坡上高出32%。坡上和坡下的土壤有机碳贮量分别为149.9和174.2t/hm2,且表层(0-40cm)碳贮量分别占整个碳贮量(0-100cm)的55%和56%。上坡和下坡的土壤有机碳含量和贮量随土层深度的加深而递减,各土层的有机碳含量和贮量均表现为下坡高于上坡。     

西藏草地生态系统植被碳贮量及其影响因子分析

在广泛收集资料的基础上,利用平均碳密度方法,估算了西藏草地生态系统中17类草地植被的碳贮量,并分析了其影响因子。结果表明:(1)17类草地植被总面积为8 205.194×10~4hm~2,草地植被总碳贮量为189.367 TgC,草地植被平均碳密度为2.308 t/hm~2,不同草地植被类型差异较大,在0.396～20.471 t/hm~2之间波动;(2)从区域分布来看,阿里、那曲、日喀则3地区,既是西藏草地主要的分布区,分布面积占西藏草地总面积的84.156%,又是西藏草地生态系统碳贮量的主要贮藏库,其中植被碳贮量占整个17类草地植被碳贮量的60.278%;(3)采用逐步回归模型和主成分分析方法,分析了气候因子对西藏草地植被碳贮量的影响程度,指出降水对草地植被碳贮量的贡献大于气温。     

黄土高原淤地坝对陆地碳贮存的贡献

我国黄土高原地区广泛分布的以防洪拦沙、淤地为目的的淤地坝工程可能在增加陆地碳贮存方面起一定作用。为验证这一假设,利用碾庄沟流域淤地坝普查资料,结合土壤侵蚀野外调查,研究了1957～2000年碾庄沟流域淤地坝控制区土壤侵蚀产沙时间空间变化与淤地坝库泥沙有机碳储存关系,并估算了黄土高原地区淤地坝拦泥对全球陆地生态系统碳收支的贡献。在研究的12个淤地坝小流域内,流域土壤侵蚀产沙平均速率为25800t/(km2·a),变异系数为42%。土壤侵蚀产沙速率的大小序列为50年代>60年代>70年代>80年代。坡地土壤侵蚀向淤地坝输沙速率(S,t/km2·a)随流域面积(A,km2)的增大呈线性函数减小(R2=0.46,p<0.05)。1957～2000年碾庄沟流域淤地坝共储存有机碳173,133t,提高流域碳储存强度在0.13～5.03t/(hm2·a)之间,平均为1.28t/(hm2·a)。到2002年底,黄土高原地区淤地坝工程共增加有机碳贮量为0.123Gt,占1994～1998年全国大面积人工造林工程增加碳贮量的17.08%,是美国年沉积泥沙有机碳储量(0.04Gt/a)的3.08倍。我们的结果表明,黄土高原地区淤地坝拦蓄泥沙及淤成的坝地是陆地生态系统重要的碳吸收汇之一。     

南京市不同土地利用方式的碳储量与碳通量

通过集成区域碳储量和碳通量的核算方法,建立不同土地利用方式与碳过程的对应关系,并以南京市为例探讨不同土地利用方式的碳储量和碳通量状况。主要结论为:(1)南京市2009年总碳储量为6 936.79万t,其中,居民点及工矿用地碳储量占总碳储量的38%,单位面积碳储量最大(184.00t/hm2)的为居民点及工矿用地,这主要归因于城市住宅建筑木材和城市绿化碳储量的大幅增加,以及建筑容积率提高带来的城市单位建筑面积碳蓄积量的增加;(2)南京市碳输入和碳输出通量最大的地类均为居民点及工矿用地,2009年分别达到3 126.95万t和3 283.20万t,两者的强度分别为218.65t/hm2和229.58t/hm2,这表明,作为人为活动强烈集中的地类,居民点及工矿用地与外界的碳交换远远高于其他地类;(3)南京市人为碳排放强度增幅明显,2009年达到46.63t/hm2,其中居民点及工矿用地高达200.52t/hm2,这说明南京市建成区碳代谢强度明显提高,碳循环压力逐渐增大。     

河北省青龙满族自治县2005-2050年森林植被碳储量及碳密度估算

基于河北省青龙满族自治县第七次森林资源清查数据,运用生物量转换因子法和平均生物量法,结合不同树种的分子式含碳率,估算了2005年青龙满族自治县森林植被碳储量和碳密度;利用回归分析法拟合青龙满族自治县林龄与碳密度之间的曲线关系。以2005年为基准年,假定林分面积保持不变,林木保持生长,推算2020年、2030年、2050年青龙满族自治县林分的碳储量和碳密度。研究结果表明:2005年青龙满族自治县森林植被碳储量为255.5万t,平均碳密度为10.73t/hm2,植被碳储量和碳密度大体呈现"北部和东南部山区较高,中部河谷丘陵地带低"的空间格局,植被碳密度国有林场高于其他乡镇;油松、灌木、柞树和经济林是青龙满族自治县森林植被碳储量的主体;2020年、2030年、2050年青龙满族自治县林分的碳储量分别为181.57万t,256.37万t,398.25万t,林分碳储量保持稳定增长的趋势。     

太行山区不同土地利用方式下土壤碳贮量的研究

通过实测对比分析了太行山区不同土地利用方式下土壤有机碳贮量的变化。研究结果表明：（1）不同土地利用方式下，土壤有机碳含量有明显差异，总的趋势是经济林（板栗林）〉水土保持林〉农田；（2）各种土地利用方式下，土壤有机碳和有机碳密度均随土壤深度增加呈现递减的趋势，但土地利用方式不同，其减少程度不同，农田土壤有机碳含量在土层深度上变化较小；（3）研究区域土壤总碳贮量为41573．67t，土壤碳贮量以经济林（板栗林）最大，达到了46．02％，水土保持林次之，而农田贡献最小，仅占5．43％。分析表明：土地利用方式对陆地生态系统碳贮量有明显影响，通过调整土地利用方式可以增加土地生态系统的碳贮量；经济林虽然人为干扰较为强烈，但由于人为投入较大，土壤碳贮量仍能保持较高的水平。     

贵州主要作物固碳现状和潜力估算

近年来,农田土壤碳固定的研究已经成为国际全球气候变化研究的一个重要热点。为明确贵州农田主要作物固碳潜力,借鉴经验公式对贵州主要农作物碳固定和生产过程中的碳排放进行测算。结果表明,近10年贵州6种作物的总固碳量平均(1 151.16±62.99)万t.a-1,变幅为1 052.65万～1 268.28万t.a-1,呈波动变化缓慢增加趋势,主要作物间接碳排放量为(48.53±1.82)万t.a-1,变幅为45.87万～51.68万t.a-1,只相当于固碳量的4.21%。贵州农田作物的固碳潜力巨大。     

湖南永顺闽楠人工林生态系统碳贮量及其分布特征

对湖南永顺43年生闽楠人工林生态系统生物量、碳贮量及其空间分布进行研究,采用平均标准木法和收获法对林分生物量及林下植被与枯落物生物量进行测定与估算,同时测定植物、土壤有机碳含量。结果表明:闽楠人工林林分生物量为295.65t/hm2,生物量分布表现为乔木层(96.70%)枯落物层(2.77%)灌木层(0.46%)草本层(0.07%)。闽楠各器官的碳素含量范围为440.83~506.01g/kg,排列顺序为树叶根茎粗根树枝细根树干树皮中根;闽楠韧皮部平均碳素含量低于外表皮,初生嫩叶碳素含量比多年生老叶高;灌木层植物的碳素平均含量为454.39g/kg,草本层植物为448.66g/kg,未分解枯落物为490.23g/kg,半分解枯落物为402.32g/kg;0-60cm土壤层有机碳含量平均值为16.53g/kg。闽楠人工林生态系统总碳贮量为288.98t/hm2,其中乔木层为133.98t/hm2(46.36%),灌木层为0.62t/hm2(0.45%),草本层为0.10t/hm2(0.07%),枯落物层为3.54t/hm2(2.56%),土壤层为150.74t/hm2(52.17%);闽楠各器官的碳贮量与其生物量成正比,树干的生物量最大,其碳贮量也最高,占乔木层碳贮量的59.33%。闽楠人工林乔木层年净生产力为11.25t/hm2,年净固碳量为5.44t/hm2,年净碳素累积量为3.12t/hm2,并且以地上部分为主。研究表明,在对区域尺度森林植被碳贮量估算时,取50%或45%作为通用标准,可能会导致估算结果偏低或偏高;闽楠人工林生态系统具有较高的碳汇能力,其系统碳贮量高于我国森林生态系统平均碳贮量(258.82t/hm2)。     

森林生态系统碳循环研究进展

针对森林生态系统碳循环在全球碳循环中的重要作用,综述了国内外森林生态系统碳循环的研究进展,包括森林生态系统植物和土壤碳固定、森林群落和土壤的碳释放、森林生态系统碳平衡和碳循环模型等方面,并指出今后的研究方向。     

How do environmental factors and different fertilizer strategies affect soil CO2 emission and carbon sequestration in the upland soils of southern China?

Upland soils have been identified as a major CO₂ source induced by human activities, such as fertilizer applications. The aim of this study is to identify the characteristics of soil CO₂ emission and carbon balance in cropland ecosystems after continuous fertilizer applications over decades. The measurements of soil surface CO₂ fluxes throughout the years of 2009 and 2010 were carried out based on a fertilization experiment (from 1990) in a double cropping system rotated with winter wheat (Triticum aestivum L.) and maize (Zea mays L.) in upland soil in southern China. Four treatments were chosen from the experiment for this study: no-fertilizer application (SR), nitrogen–phosphorus–potassium chemical fertilizers (NPK), NPK plus pig manure (NPKM) and pig manure alone (M). Results showed that the mean value of soil CO₂ fluxes from 08:00 to 10:00 am could represent its daily mean value in summer period (June–August) and that from 09:00 am to 12:00 pm for the rest season of a year. Soil temperature and moisture combined together could explain 70–83% of variations of CO₂ emission. Annual cumulative soil CO₂ fluxes in the treatments with manure applications (8.2 ± 0.8 and 11.0 ± 1.2 t C ha⁻¹ in 2009, and 7.9 ± 0.9 and 11.1 ± 1.2 t C ha⁻¹ in 2010 in NPKM and M, respectively) were significantly higher than those in the treatments with non-manure addition (2.5 ± 0.2 and 3.4 ± 0.2 t C ha⁻¹ in 2009, and 2.1 ± 0.2 and 3.7 ± 0.3 t C ha⁻¹ in 2010 in SR and NPK, respectively). However, the treatments with manure applications represented a carbon sink in the soil (carbon output/input ratio < 1.0), which demonstrated potential for carbon sequestration.     

Protection of soil carbon by microaggregates within earthworm casts

Earthworms are known to play a role in aggregate formation and soil organic matter (SOM) protection. However, it is still unclear at what scale and how quickly earthworms manage to protect SOM. We investigated the effects of Aporrectodea caliginosa on aggregation and aggregate-associated C pools using ¹³C-labeled sorghum (Sorghum bicolor (L.) Moench) leaf residue. Two incubations were set up. The first incubation consisted of soil samples crushed <250 μm to break up all macroaggregates with three treatments: (i) control soil; (ii) soil+¹³C-labeled residue and (iii) soil+¹³C-labeled residue+earthworms. Earthworms were added after 8 d and 12 d (days) later, aggregate size distribution was measured together with total C and ¹³C in each aggregate fraction. A second incubation was made to assay protected versus unprotected total C and ¹³C from 21-d laboratory incubations of intact and crushed large (>2000 μm) and small (250-2000 μm) macroaggregates and microaggregates (53-250 μm). Eight different pools of aggregate-associated C were quantified: (1) and (2) unprotected C pools in large and small macroaggregates, (3) unprotected C pools in microaggregates, (4) and (5) protected C pools in large and small macroaggregates, (6) protected C pool in microaggregates, and (7) and (8) protected C pools in microaggregates within large and small macroaggregates. In the presence of earthworms, a higher proportion of large macroaggregates was newly formed and these aggregates contained more C and ¹³C compared to bulk soil. There were no significant differences between the samples with or without earthworms in the C pool-sizes protected by macroaggregates, microaggregates or microaggregates within small macroaggregates. However, in the presence of earthworms, the C protected by microaggregates within large macroaggregates was a significant pool and 22% of this C pool was newly added C. In conclusion, these results clearly indicate the direct involvement of earthworms in providing protection of soil C in microaggregates within large macroaggregates leading to a possible long-term stabilization of soil C.     

我国湿地碳循环的研究进展

湿地生态系统的碳循环正成为全球变化与陆地生态系统碳循环研究中的一大热点,在稳定全球气候变化中占有重要地位,其重要性主要表现在湿地土壤是陆地重要的有机碳库,土壤碳密度高,能够相对长期地储存碳,是多种温室气体的源和汇。目前湿地碳循环的研究主要集中在碳循环的影响因素方面,对我国湿地土壤有机碳储存的变化及其空间分布规律的特点研究较少。本文通过文献综述,研究我国不同气候区湿地土壤有机碳的储存变化及空间分布规律,对于了解湿地土壤有机碳的储存特点及其与陆地生态系统碳循环的关系,评价和保护湿地生态系统都具有重要的科学意义。     

Carbon sequestration in the agricultural soils of Europe

In this review, technical and economically viable potentials for carbon sequestration in the agricultural soils of Europe by 2008-2012 are analysed against a business-as-usual scenario. We provide a quantitative estimation of the carbon absorption potential per hectare and the surface of agricultural land that is available and suitable for the implementation of those measures, their environmental effects as well as the effects on farm income. Realistically, agricultural soils in EU-15 can sequester up to 16-19 Mt C year⁻¹ during the first Kyoto commitment period (2008-2012), which is less than one fifth of the theoretical potential and equivalent to 2% of European anthropogenic emissions. We identified as most promising measures: the promotion of organic inputs on arable land instead of grassland, the introduction of perennials (grasses, trees) on arable set-aside land for conservation or biofuel purposes, to promote organic farming, to raise the water table in farmed peatland, and—with restrictions—zero tillage or conservation tillage. Many options have environmental benefits but some risk of increasing N₂O emissions. For most measures it is impossible to determine the overall impact on farm profitability. Efficient carbon sequestration in agricultural soils demands a permanent management change and implementation concepts adjusted to local soil, climate and management features in order to allow selection of areas with high carbon sequestering potential. Some of the present agricultural policy schemes have probably helped to maintain carbon stocks in agricultural soils.     

减量施氮与间作大豆对蔗田碳平衡特征的影响

为了研究氮肥投入及豆科作物间作对蔗田碳汇的影响,通过2年(2012—2013年)的大田试验,采用投入产出平衡法(即将作物生育期内的碳投入与碳产出进行量化分析),探讨2个蔗田施氮水平[300 kg·hm?2(减量施氮)和525 kg·hm?2(常规施氮)]和4种种植模式(甘蔗单作、大豆单作、甘蔗||大豆1行︰1行间作及甘蔗||大豆1行︰2行间作)下蔗田生态系统碳的输入和输出特征。结果表明,两种施氮处理甘蔗||大豆1︰2间作模式碳输入量均显著高于甘蔗单作和甘蔗||大豆1︰1间作模式。2012年减量施氮处理甘蔗||大豆1︰2间作模式碳输出量显著低于甘蔗单作和甘蔗||大豆1︰1间作模式,2013年差异不显著;甘蔗收获后,减量施氮处理甘蔗||大豆两种间作模式土壤碳截存量均显著高于甘蔗单作。甘蔗||大豆间作生态系统的碳收支与平衡分析表明,减量施氮处理甘蔗||大豆1︰2间作模式净碳固定量2012年为2 956.35 kg·hm?2,2013年为872.59 kg·hm?2。减量施氮处理甘蔗||大豆1︰2间作模式下农田固碳潜力大于其他处理,从农业可持续发展角度考虑,该模式具有一定的生态合理性。     

基于LUCC的四川省主体功能区碳排放与生态补偿研究

土地利用/土地覆被变化（LUCC）影响下的碳排放充分体现人类活动对生态环境的扰动程度,由此切入的碳收支与补偿研究对区域低碳经济与平衡发展具有重要意义。本文以2005年和2015年四川省土地利用数据为基础,参考IPCC假定构建碳排放模型,借助GIS平台运用数学模型对四川省5个主体功能区碳排放及碳补偿率进行测度与分析,采用造林成本法和碳税率法对生态补偿标准进行测算。结果表明：1）研究期内四川省各主体功能区土地利用与主体功能区规划相符并按其功能定位优化发展。重点开发区域耕地占绝对优势,建设用地面积的总量和增量最大;重点生态功能区林地、草地占比最大。2）研究期内各主体功能区的总碳排放量大幅度增加。重点开发区域碳源量、总碳排放量及其增量均居首位;重点生态功能区碳吸收的能力减弱。3）各主体功能区建设用地碳排放强度远大于总碳排放强度,研究期内各主体功能区总碳排放强度均增加,建设用地碳排放强度则有增有减。国家层面重点开发区域总碳排放强度最大,建设用地碳排放强度很小。4）生态发展区碳补偿率高,经济发达区低。国家层面限制开发区域（重点生态功能区）碳吸收补偿系数最高。5）碳源区应对作为碳汇区的甘孜藏族自治州按固碳价格进行生态补偿。碳排放量与各主体功能区功能定位高度相关,生态补偿标准大致从成都平原向四周递减,限制开发区域生态补偿标准偏低。基于碳排放的生态补偿标准建立横向财政转移支付政策,有利于四川省节能减排和平衡发展。     

农田土壤有机碳固定机制及其影响因子研究进展

全球气候变暖引起的环境问题已经引起各国政府及科学家的密切关注。农田土壤作为大气CO2的源和库,在全球碳循环中的重要角色日渐被认识。本文围绕土壤固碳的基本问题,总结了农田土壤固碳潜力、土壤有机碳固定机制及其影响因素的国内外研究进展。国内研究表明,目前耕地的地力不稳,土壤有机碳密度较低,农田土壤固碳的潜力较大。因此,加强不同区域农田土壤固碳潜力、固碳过程、固碳机理等方面的研究,设计合理优化的农业管理措施,是今后研究的重点。     

Impacts of management on decomposition and the litter-carbon balance in irrigated and rainfed no-till agricultural systems

The litter carbon (C) pool of a single litter cohort in an agroecosystem is the difference between net primary productivity and decomposition and comprises 11–13% of the total C pool (litter and soil 0–15 cm depth) post-harvest. This litter-C pool is highly dynamic and up to 50% can be decomposed in the first 12 months of decomposition. Thus, understanding litter-C dynamics is key in understanding monthly and annual total ecosystem carbon dynamics. While the effects of management practices such as irrigation and fertilization on productivity are well understood, the effects on decomposition are less studied. While irrigation and fertilization increase productivity, this will only lead to increased litter-C residence time and litter-C pool accretion if these techniques do not also result in equivalent or greater increases in decomposition. Management could potentially have impacts on litter-C accretion by increasing litter inputs, changing plant-C allocation, plant tissue quality, or decomposition rates. We examined carbon loss of one annual cohort of maize litter using in situ nylon litter bags for 3 years in three no-till fields with differing management regimes: irrigated continuous maize with a pre-planting fertilization application and two fertigation events, irrigated maize–soybean rotation with the same fertilization regime as the irrigated continuous maize management regime, and rainfed maize–soybean rotation with a single pre-planting fertilization event. We addressed the effects of these different management regimes on net primary productivity and litter inputs, litter nitrogen (N) concentrations and carbon quality measures, plant C allocation, decomposition rates and the potential changes in the overall litter-C balance. We found that irrigation/fertigation management increased litter inputs, led to changes in plant tissue quality, had no effect on carbon allocation, and increased decomposition rates. This balance of both greater litter inputs and outputs of C from the irrigated management regimes led to a similar litter-C balance for this litter cohort in the irrigated and rainfed management regimes after 3 years of decomposition. Our data clearly show that merely increasing litter-C inputs through irrigation/fertigation practices is not sufficient to increase litter-C residence time because decomposition rates also increase. Therefore, close monitoring of decomposition rates is essential for understanding litter-C pool dynamics.     

Old soil carbon is more temperature sensitive than the young in an agricultural field

Changes in the carbon stock of soil in response to climate change would significantly affect the atmospheric carbon dioxide concentration and consequently climate. The isotopes of carbon provide a means to study the temperature sensitivities of different soil carbon fractions. Where C3 vegetation has changed for C4, soil organic matter (SOM) from the different origins have different ¹³C/¹²C ratios. Relying on this feature, we took soil samples from a control field and a field where ordinary grain (C3) vegetation was replaced by maize (C4), 5 years ago. We measured the respiration rate and the ¹³C/¹²C ratio of the CO₂ produced by the samples at different temperatures. Based on these measurements, we quantified that Q₁₀ was 3.4-3.6 for the total CO₂ production while it was 2.4-2.9 at 20 °C for the maize-derived young carbon and 3.6 for the older C3-derived carbon. Our results suggest that climatic warming will accelerate especially the decomposition of the large pool of old soil carbon in these fields.