华东稻麦轮作生态系统的N2O排放研究

根据对华东稻麦轮作周期的N₂O排放及其影响因子的连续观测结果,分析了N₂O排放时间变化以及施肥、灌溉、温度、土壤湿度和土壤速效N素含量对N₂O排放的影响,同时还比较分析了稻田N₂O和CH₄排放.研究结果表明,稻麦轮作周期内,水稻生长季的N₂O排放量仅占30%,稻田持续淹水可比常规灌溉增加CH₄排放量26%,减少N₂O排放量11～26%.     

广州地区晚稻田CH4和N2O的排放通量及其影响因素

用密闭箱法同时研究了广州地区晚稻田CH4和N2 O的排放通量。结果表明 ,连续淹水、常规连作和水旱轮作等 3种处理的CH4平均排放通量分别为 1 7 63、2 84和0 36mg·m- 2 ·h- 1 ,而N2 O的平均排放通量分别为 6 74、1 1 69和 55 0 7μgN2 O N·m- 2 ·h- 1 ,表明稻田连续淹水显著增加CH4的排放而降低N2 O的排放。水旱轮作降低CH4排放而提高N2 O的排放 ,说明稻田CH4和N2 O排放之间存在着消长关系。讨论了这 2种温室气体排放的影响因素 ,并初步分析了它们对温室效应的相对贡献。     

华南丘陵地区农林复合生态系统晚稻田甲烷和氧化亚氮排放

采用静态箱-气相色谱法对晚稻田甲烷(CH4)和氧化亚氮(N2O)排放进行田间原位测定。结果表明,有植株参与的稻田CH4排放通量季节变化与地下5cm温度呈显著正相关关系。稻田CH4和N2O季节平均排放通量在有植株参与时分别为1.16±0.38mgm-2h-1和42.33±20.00μgm-2h-1,而无植株参与的分别为0.15±0.11mgm-2h-1和51.69±15.87μgm-2h-1。水稻种植对CH4的排放影响较大,对N2O的排放影响较小,有植株参与的稻田CH4平均排放量显著高于无植株参与的稻田,N2O的平均排放量无显著差异。     

施硅对增温稻田CH4和N2O排放的影响

夜间增温幅度大于白天是气候变暖的显著特征。夜间增温影响水稻生产及CH4和N2O排放。硅是作物有益元素,施硅可提高产量,减少稻田CH4排放。增温或施硅单因子对稻田CH4和N2O排放影响已有报道,但二者耦合如何影响水稻生产及稻田CH4和N2O排放,尚不清楚。通过田间模拟试验,研究了夜间增温下施硅对水稻生长、产量及温室气体持续增温/冷却潜势和排放强度的影响。采用铝箔反光膜夜间(19:00-6:00)覆盖水稻冠层进行模拟夜间增温试验。增温设2水平,即常温对照(CK)和夜间增温(NW);施硅量设2水平,即Si0(不施硅)和Si1(钢渣硅肥,200 kgSiO2/ha)。结果表明,施硅可缓解夜间增温对水稻根系活力的抑制作用,降低夜间增温对水稻地上部、地下部干重和产量的抑制作用。夜间增温显著提高CH4累计排放量,而施硅显著降低CH4累计排放量。夜间增温下施硅处理稻田CH4累计排放量在分蘖期、拔节期、抽穗-扬花期和灌浆成熟期比未施硅处理分别低48.12%、49.16%、61.59%和39.13%。夜间增温或施硅均促进稻田N2O排放,夜间增温下施硅在上述生育期以及全生育期的累计排放量依次比对照高78.17%、51.45%、52.01%、26.14%和40.70%。研究认为,施硅可缓解夜间增温对稻田综合增温潜势和排放强度的促进作用。     

采伐对小兴安岭落叶松-泥炭藓沼泽温室气体排放的影响

利用静态箱-气相色谱法,研究了择伐和皆伐对小兴安岭落叶松-泥炭藓沼泽CH4、CO2、N2O排放的影响.结果表明:采伐改变了落叶松-泥炭藓沼泽CH4和N2O的季节排放规律,其中对照样地的CH4为夏季吸收、秋季排放,N2O夏秋季吸收;择伐样地的CH4和N2O在夏季集中排放;皆伐样地的CH4在夏秋季排放,N2O则在夏季吸收、秋季排放.但采伐对CO2季节排放规律的影响,均为夏季春季秋季.采伐改变了CH4、CO2和N2O的源汇功能,对照样地为CO2的排放源、CH4和N2O的弱吸收汇;采伐地的CO2排放量下降了1/4,并转化为N2O弱排放源,为CH4的弱排放源或强排放源.择伐样地温室效应贡献潜力较对照样地下降了24.5%,皆伐地则提高了3.2%.     

应用DNDC模型分析管理措施对稻麦轮作系统CH4和N2O综合温室效应的影响

以南京地区稻麦轮作体系为对象,研究了不同农业管理措施对CH4和N2O排放通量及年度动态变化的影响,用田间观测数据验证生物地球化学循环模型(DNDC)在该耕作制度下的适用性;利用DNDC模型模拟不同环境因子和管理措施对CH4和N2O综合温室效应(GWP)的影响.结果表明:除了对照和麦季对CH4排放的模拟偏差较大外,DNDC对其余各处理模拟的CH4和N2O累积排放量与田间观测结果基本吻合,相对偏差变幅7.1%～26.3%,可以直接应用DNDC模型模拟环境因子和主要管理措施对CH4和N2O累积排放量引起GWP的影响.模型灵敏度检验结果表明,年均温度、土壤容重、土壤有机碳、土壤质地、土壤pH等环境因子对GWP的影响显著;施用氮肥、秸秆还田量和烤田期长短等管理因子对GWP的影响明显.在估算我国稻麦轮作制度下温室气体的点或区域排放规律时,应考虑上述这些影响因子.     

小兴安岭典型草丛沼泽湿地CO2、CH4和N2O的排放动态及其影响因素

2007年6～10月,采用静态箱-气相色谱法,同步研究了小兴安岭典型修氏苔草(Carex schmidtii)沼泽湿地CO2、CH4和N2O排放通量的季节动态及其与环境因子的关系,估算CO2、CH4和N2O的生长季排放量,探讨了沼泽湿地碳与氮的源汇关系.结果表明:草丛沼泽生长季节温室气体排放量以CO2占绝对优势(99.61%),CH4的排放量次之(0.39%),N2O的排放量最低(0.000 7%),且为碳、氮的吸收汇(分别为固定量的53.93%和0.04%);CO2、CH4和N2O生长季平均排放通量依次为487.89、1.88和0.004 mg·m-2·h-1,且具有明显的季节变化特征,CO2和N2O的最高排放量均出现在夏季(6月24日至8月14日和7月14日至8月14日),CH4的最高排放量出现在夏秋季(8月24日至9月24日),其中,CO2季节变化与空气温度和0～20 cm土壤温度具有显著相关性(p＜0.05),CH4与空气温度具有显著相关性(p<0.01),N2O与水位具有显著的负相关性(p＜0.05).     

稻田CH4和N2O排放关系及其微生物学机理和一些影响因子

用静态箱法原位观测和分析了我国北方稻田 3～ 1 2月CH4和N2 O的排放及其关系 ,并研究了这一关系发生的微生物学机理 .同时 ,监测了土壤湿度、pH、水分及Eh的变化 .结果表明 ,稻田CH4和N2 O排放之间存在着互为消长的关系 (R2 =0 0 4 94) .土壤湿度、pH及Eh变化范围分别在 0～ 2 4℃、6 87～ 7 0 2和 41 5～ 30 0mv之间 ,水分从非淹水期的 38～ 72 ?至 5～ 1 0cm浅水淹灌 .土壤Eh对CH4和N2 O的释放起重要的调控作用 .在整个观测期内 ,与CH4和N2 O释放密切相关的 6种菌群 (发酵细菌、产氢产乙酸细菌、产甲烷细菌、甲烷氧化菌、硝化细菌、反硝化细菌 )各有其数量消长及酶活性变化规律 ,稻田CH4和N2 O排放之间互为消长的关系受这些相关微生物数量及酶活性变化的共同调控 .     

长效氮肥施用对黑土水旱田CH4和N2O排放的影响

通过在黑土玉米地与水稻田施用长效氮肥后发现 ,长效碳酸氢铵 (长碳 )与长效尿素(长尿 )能显著减少黑土玉米地N2 O的排放。与施用普通尿素相比 ,其排放量分别减少了5 9 2 %和 73 3%。长碳和长尿还能促进黑土玉米地对CH4的吸收作用。黑土水稻田施用长尿后 ,N2 O的排放减少了 6 1%。而CH4的排放却略有增加     

DCD不同施用时间对水稻生长期CH4和N2O排放的影响

硝化抑制剂传统的施用方法是在作物移栽或播种前与基肥配合施用.通过温室盆栽试验研究相同施肥条件下,硝化抑制剂双氢胺(dicyandiamide, DCD)不同施用时间(与基肥混施、分孽肥后施入、穗肥后施入)对水稻生长期CH4和N2O排放的影响.结果表明,施入DCD能同时降低CH4和N2O排放量.就整个水稻生长期而言,与基肥混施DCD分别降低21.41%的CH4排放量和8.00%的N2O排放量;调节DCD施用时间至分孽肥后显著降低30.30%的N2O排放量,同时降低5.24%的CH4排放量.就施入DCD到水稻收获的特定生长阶段而言,缓施DCD分别降低32.65%的N2O排放量和11.18%的CH4排放量;晚施DCD对CH4和N2O排放的影响不大.CK、早施DCD、缓施DCD及晚施DCD处理CH4平均排放通量分别为0.95、0.75、0.87 mg/(m2 · h)及0.94 mg/(m2 · h),N2O平均排放通量为155.67、143.24、108.50 μg/(m2 · h)及153.24 μg/(m2 · h),缓施DCD显著降低CH4和N2O排放量(p＜0.01).土壤温度是影响N2O排放的主要因素,而CH4排放通量与土壤Eh呈显著负相关(p＜0.01).     

Recent progress on polymerization-induced emission

The aggregate luminescence behaviors of polymeric luminescent materials have been attracting great attention. However, the importance of the polymerization process on luminescence, namely, polymerization-induced emission (PIE), has rarely been overviewed. In this review, recent advances in polymerization with PIE effects are summarized, including PIE with aromatic rings based on one-/two-/multi-component polymerizations, and PIE without aromatic rings according to disparate mechanisms of polymerizations. Typical examples are selected to elaborate the basic design principles, as well as the properties and potential applications of the luminous polymers. Moreover, the challenges and perspectives in this area are also discussed.     

骨导声诱发的耳声发射耳蜗图

用不同频率的短纯音骨导刺激,在7名(14耳)听力正常受试者同时记录双耳声诱发耳声发射(EOAE)。此法比单耳轮流记录省时一半。研究结果表明,EOAE 为一种窄带声,其中心频率随刺激声频率增高而增高,提示 EOAE 产生部位在接受刺激声频率对应的耳蜗部位附近。EOAE 的潜伏期与刺激强度无明显关系,但有随刺激声频率增高而变短的趋势,可能与不同频率刺激声诱发的 EOAE 在基底膜上产生的部位与鼓膜之间的距离不等有关。除1耳用4.0kHz 外,用1.0,2.0,3.0和4.0kHz 短纯音刺激在14耳全可记录到 EOAE,0.5kHz和6.0kHz 则分别在10耳和7耳记录到 EOAE。0.5—6.0kHz 短纯音诱发的 EOAE 的阈值均值连线所得的声发射耳蜗图上可见,1.0kHz 处阈值最低,而在这些受试者所测得的中耳共振频率平均值为1100±230Hz,推测1.0kHz EOAE 阈值最低与中耳的传导函数有关。本文描述的骨导双耳同时记录 EOAE 并描记声发射耳蜗图的方法可用于临床的听力客观评价。     

Recent advances of organic emitters in deep-red light-emitting electrochemical cells

Light-emitting electrochemical cells (LECs) are kind of easily fabricated and low-cost light-emitting devices that can efficiently convert electric power to light energy. Compared with blue and green LECs, the performance of deep-red LECs is limited by the high non-radiative rate of emitters in long-wavelength region. While various organic emitters with deep-red emission have been developed to construct high-performance LECs, including polymers, metal complexes, and organic luminous molecules (OLMs), but this is seldom summarized. Therefore, we overview the recent advances of organic emitters with emission at the deep-red region for LECs, and specifically highlight the molecular design approach and electrochemiluminescence performance. We hope that this review can act as a reference for further research in designing high-performance deep-red LECs.     

湿地碳排放及其影响因素

湿地生态系统在全球碳循环中起着重要作用.湿地独特的土壤、水文和植被条件,使得其在低氧环境下能不断累积碳,并同时释放大量温室气体——CH4和CO2,因此湿地的碳排放近年来成为全球气候变化研究关注的重点问题.湿地的土壤状况、水文条件及植被类型的不同导致湿地CH4和CO2的排放具有极强的时空变异性.土壤温度与CH4和CO2排放呈正相关关系;水位条件对湿地温室气体的排放有一定影响,在一定范围内,土壤的厌氧环境导致CH4排放量增大,CO2排放量减小;植被影响到温室气体产生、氧化和排放各个方面,因物种而异.     

中国农田土壤N2O排放通量分布格局研究

中国作为世界上一个重要农业大国,对全球大气中N2O浓度的影响正在引起人们的普遍关注。该研究采用针对农业土壤痕量气体排放估算建立的,基于N2O的产生、传输和消耗机理的反硝化分解（DNDC）模型,在建立了有关中国气候、农业土壤和农业生产的分县数据库基础上,估计了我国各县农业土壤N2O的排放通量,发现我国农田土壤N2O排放通量有较明显的地区差异,西北地区较低,东南地区较高。还发现无论温度升高,还是施肥量变化,对我国农田土壤N2O排放通量的影响,都存在区域差异,表现为东南地区的变化幅度较西北地区大,这可能与我国气候的干湿变化有较密切的关系。     

Effect of agrometeorological parameters on the phenology of pollen emission and production of olive trees (Olea europea L.)

The pollination period and pollen concentrationof olive trees (Oleaeuropea L.) and olive production were analysedfor Prato and Florenceusing a data set of 8 years (1991–1998).Meteorological data have been usedto obtain information about weather conditionsduring vegetative seasonsand correlations were found both for thephenology and yield.The results showed that air temperatureprevious to the onset of floweringis of great importance in determining thereproductive cycle of olive treebut the chill period in January and Februaryshould also be considered.Olive pollen collected during thepollination period was positivelycorrelated with the production level for bothsites. Weather conditionfollowing pollination were also taken intoaccount for a better assessmentof the final yield.     

Environmental and developmental controls over the seasonal pattern of isoprene emission from aspen leaves

Isoprene emission from plants represents one of the principal biospheric controls over the oxidative capacity of the continental troposphere. In the study reported here, the seasonal pattern of isoprene emission, and its underlying determinants, were studied for aspen trees growing in the Rocky Mountains of Colorado. The springtime onset of isoprene emission was delayed for up to 4 weeks following leaf emergence, despite the presence of positive net photosynthesis rates. Maximum isoprene emission rates were reached approximately 6 weeks following leaf emergence. During this initial developmental phase, isoprene emission rates were negatively correlated with leaf nitrogen concentrations. During the autumnal decline in isoprene emission, rates were positively correlated with leaf nitrogen concentration. Given past studies that demonstrate a correlation between leaf nitrogen concentration and isoprene emission rate, we conclude that factors other than the amount of leaf nitrogen determine the early-season initiation of isoprene emission. The late-season decline in isoprene emission rate is interpreted as due to the autumnal breakdown of metabolic machinery and loss of leaf nitrogen. In potted aspen trees, leaves that emerged in February and developed under cool, springtime temperatures did not emit isoprene until 23 days after leaf emergence. Leaves that emrged in July and developed in hot, midsummer temperatures emitted isoprene within 6 days. Leaves that had emerged during the cool spring, and had grown for several weeks without emitting isoprene, could be induced to emit isoprene within 2 h of exposure to 32°C. Continued exposure to warm temperatures resulted in a progressive increase in the isoprene emission rate. Thus, temperature appears to be an important determinant of the early season induction of isoprene emission. The seasonal pattern of isoprene emission was examined in trees growing along an elevational gradient in the Colorado Front Range (1829–2896 m). Trees at different elevations exhibited staggered patterns of bud-break and initiation of photosynthesis and isoprene emission in concert with the staggered onset of warm, springtime temperatures. The springtime induction of isoprene emission could be predicted at each of the three sites as the time after bud break required for cumulative temperatures above 0°C to reach approximately 400 degree days. Seasonal temperature acclimation of isoprene emission rate and photosynthesis rate was not observed. The temperature dependence of isoprene emission rate between 20 and 35°C could be accurately predicted during spring and summer using a single algorithm that describes the Arrhenius relationship of enzyme activity. From these results, it is concluded that the early season pattern of isoprene emission is controlled by prevailing temperature and its interaction with developmental processes. The late-season pattern is determined by controls over leaf nitrogen concentration, especially the depletion of leaf nitrogen during senescence. Following early-season induction, isoprene emission rates correlate with photosynthesis rates. During the season there is little acclimation to temperature, so that seasonal modeling simplifies to a single temperature-response algorithm.     

Seasonal characteristics of nitric oxide emission from a typical Chinese rice–wheat rotation during the non-waterlogged period

Nitric oxide emissions from a typical rice–wheat rotation system in southeastern China were continuously measured with an automatic system in 1996–1997. The seasonal pattern of the NO emissions was characterized for the non‐waterlogged period of a rotation cycle. Nitric oxide emissions during the period from March through June were 3.9–6.3 folds for the fertilized plots and 1.6 folds for the unfertilized plot larger than those from November through December. Nitric oxide emissions were not detectable during the winter period from January through February. Amendment of synthetic fertilizer N significantly enhanced the NO emission by a factor of 6.5, but the enhancement was significantly mitigated by 25% through substituting ca. 16% of the synthetic fertilizer N with organic N from fermented crop residues or by 21% through deep tillage. The NO–N emission factor, defined as the amount of NO–N released per unit of synthetic fertilizer N input, was determined to be 0.025 kg NO–N kg ^?1 of N applied for the non‐waterlogged period, which was reduced by 32% through substituting part of the synthetic N fertilizer with fermented crop residues or by 24% through deep tillage. In addition, the NO emission factor, defined as the amount of NO–N emitted from unit unfertilized area per day, was observed to be ca. 3.8 g N ha ^?1 d ^?1 . Approximately 0.55 Tg N yr ^?1 was likely released as NO from Chinese cultivated lands.     

Comparison of farm-level greenhouse gas emissions in transhumance and semi-intensive sheep production systems in continental rangelands

Despite their predominance worldwide, few studies have been conducted to look at the impact of sheep production systems relying on transhumance practices in arid and continental conditions, on farm-level greenhouse gas (GHG) emissions. Using Turkey as an example, this paper examines on farm-level GHG emissions calculated for two contrasting sheep production systems under arid and continental climate conditions. Production and management data were obtained through face-to-face interviews carried out on 10 transhumance and 15 semi-intensive meat sheep farms in Turkey. A total of seven GHG emission estimates were then calculated for each farm with the Agricultural Resource Efficiency Calculator (AgRECalc©) tool; i) total Carbon Dioxide (CO2) from energy use (kg CO2e), ii) total Carbon Dioxide equivalent (CO2e) from methane (kg CO2e), iii) total CO₂e from nitrous oxide (kg CO₂e), iv) whole farm and enterprise CO₂e emissions (kg CO₂e), v) net emission from land use (kg CO₂e), vi) whole farm CO₂e emissions per kg of farm output (kg CO₂e/kg output), vii) product CO₂e emissions (meat): kg CO₂e / kg live weight, and viii) farm output (kg of sheep). Multivariate analyses (using R software) were carried out to compare both farm types and their respective carbon emissions. The total farm output per ewe was lower in the transhumance farms (7.4 kg/ewe) than in the semi-intensive farms (7.7 kg/ewe). The kg CO₂e per kg of output was also lower for the transhumance farms (46.2 kg CO₂e) than for the semi-intensive ones (56.5 kg CO₂e). This trend was similar for the amount of CO₂e per kg of live weight produced (20.8 kg and 25.4 kg for the transhumance and the semi-intensive farms, respectively). Despite overall net emissions from land use being greater on average for the transhumance farms, once measured per hectare, they were found to be lower than those for the semi-intensive farms. This study provides a reference point for different sheep production systems’ GHG emission impact in continental rangelands in Turkey.