猪粪化肥配施对双季稻田CH4和N2O排放及其全球增温潜势的影响

以湖南典型红壤双季稻田系统为研究对象,采用静态箱-气相色谱法研究了水稻生长季基肥配施猪粪条件下CH4和N2O的排放特征,并估算了排放的CH4和N2O的全球增温潜势(GWP).结果表明,与施用化肥处理相比,猪粪化肥配施对稻田CH4和N2O排放的季节变化模式无明显影响,但影响其排放量大小.两个稻季,猪粪替代50%化学氮肥处理(1/2N+PM)CH4累积排放量较不施氮肥处理(0N)、50%化学氮肥处理(1/2N)、100%化学氮肥处理(N)分别提高54.83%、33.85%和43.30%(P<0.05);1/2N+PM处理N2O累积排放量较N处理显著降低67.50%,较0N处理、1/2N处理分别提高129.43%、119.23%(P<0.05).水稻生长季CH4是GWP的主要贡献者,占CH4和N2O综合GWP的99%以上.1/2N+PM处理的GWP显著高于其他处理(P<0.05),且1/2N+PM处理单位产量GWP最高,较N处理、1/2N处理、0N处理分别提高58.21%、26.82%、20.63%.因此,双季稻田猪粪替代部分化学氮肥较全部施用化学氮肥增加了双季稻田CH4和N2O排放的综合温室效应,其对温室气体排放的影响需在区域温室气体排放清单中加以考虑.     

不同施氮处理下旱作农田土壤CH_4、N_2O气体排放特征研究

依托甘肃农业大学布设在定西市李家堡镇的长期施氮定位实验,对不同施氮农田CH4和N2O气体通量,采用静态箱-气相色谱法进行小麦生育期的连续观测,并对影响通量变化的环境因子同期观测.结果表明:5个施氮处理下(0、52.5、105、157.5、210 kg·hm-2),旱作农田土壤在小麦全生育期内表现为CH4累积通量的汇和N2O累积通量的源;且不施氮处理时,CH4累积吸收通量最大;施氮量为210 kg·hm-2时,土壤CH4的累积吸收通量所受抑制最大,即土壤CH4累积吸收通量随施氮量升高而降低.相反,不施氮处理时,土壤N2O的累积排放通量最小,施氮量为210 kg·hm-2时,土壤N2O的累积排放通量最大,土壤N2O累积排放通量随施氮量的增加而增大.综合分析,施氮量增大会抑制全生育期旱作春小麦田土壤CH4吸收通量,提高土壤N2O的排放通量.因此,合理控制施氮量有利于生育期旱作农田土壤减排.CH4平均吸收通量随土壤温度的升高而降低,随土壤水分的升高而升高;相反,N2O平均排放通量随土壤温度的升高而升高,随土壤水分的升高而降低.5~10 cm层次的土壤温度与CH4平均吸收通量呈极显著线性负相关,与N2O平均排放通量呈显著正相关.5~10 cm层次的土壤水分与CH4平均吸收通量呈极显著线性正相关,与N2O平均排放通量呈显著负相关.     

Methane and nitrous oxide fluxes from four tundra ecotopes in Ny-Ålesund of the High Arctic

During the summers of 2008 and 2009, net methane（CH4） and nitrous oxide（N2O） fluxes were investigated from 4 tundra ecotopes： normal lowland tundra（LT）, bird sanctuary tundra（BT）, the tundra in an abandoned coal mine（CT） and the tundra in scientific bases（ST） in Ny-Alesund of the High Arctic. Tundra soils in CT（184.5 ± 40.0 μg CH4/（m2·hr）） and ST（367.6 ± 92.3 μg CH4/（m2·hr）） showed high CH4 emissions due to the effects of human activities, whereas high CH4 uptake or low emission occurred in the soils of LT and BT.The lowland tundra soils（mean,-4.4-4.3 μg N2O/（m2·hr）） were weak N2 O sources and even sinks. Bird activity increased N2 O emissions from BT with the mean flux of7.9 μg N2O/（m2·hr）. The mean N2 O fluxes from CT（45.4 ± 10.2 μg N2O/（m2·hr）） and ST（78.8 ± 18.5 μg N2O/（m2·hr）） were one order of magnitude higher than those from LT and BT, indicating that human activities significantly increased N2 O emissions from tundra soils. Soil total carbon and water regime were important factors affecting CH4 fluxes from tundra soils. The N2 O fluxes showed a significant positive correlation with ammonia nitrogen（NH4＋-N） contents（r = 0.66, p 〈 0.001） at all the observation sites, indicating that ammonia nitrogen（NH4＋-N） content acted as a strong predictor for N2 O emissions from tundra soils. The CH4 and N2O fluxes did not correspond to the temperature variations of soil at 0-15 cm depths.Overall our results implied that human activities might have greater effects on soil CH4 and N2O emissions than current climate warming in Ny-Alesund, High Arctic.     

Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting

Gaseous emission (N₂O, CH₄ and NH₃) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO₂ and 0.8% to 7.5% of TOC emitted as CH₄. Most of the nitrogen was lost in the form of NH₃, which account for 9.6% to 32.4% of initial nitrogen. N₂O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH₃ (p = 0.0189), CH₄ (p = 0.0113) and N₂O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH₄ emission but increase the NH₃ and N₂O losses. C/N ratio could affect the NH₃ (p = 0.0442) and CH₄ (p = 0.0246) emissions significantly, but not the N₂O. Lower C/N ratio caused higher NH₃ and CH₄ emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio.     

碳底物含量对厌氧条件下水稻土N2、N2O、NO、CO2和CH4排放的影响

理解底物碳氮对厌氧条件下水稻土排放氮素气体——氮气(N2)、氧化亚氮(N2O)和一氧化氮(NO)以及二氧化碳(CO2)和甲烷(CH4)的影响,有助于制定合理的温室气体减排措施,定量了解反硝化产物组成对碳底物水平的依赖性,也有助于氮转化过程模型研发中制定正确的关键过程参数选取方法或参数化方案.本研究采用粉砂壤质水稻土为研究对象,设置对照(CK)和加碳(C+)两个处理,前者的初始硝态氮和可溶性有机碳(DOC)含量分别为~50 mg·kg-1和~28 mg·kg-1,后者的分别为~50 mg·kg-1和~300 mg·kg-1.采用氦环境培养-气体及碳氮底物直接同步测定系统,研究了完全厌氧条件下碳底物水平对上述气体排放的影响.结果表明,CK处理无CH4排放,而C+处理可观测到CH4排放;C+处理的综合增温潜势显著高于CK处理(P<0.01);NO、N2O和N2排放量占这3种氮素气体排放总量的比重,在CK处理分别约为9%、35%和56%,在C+处理分别约为31%、50%和19%,处理间差异显著(P<0.01).由此表明,碳底物水平可显著改变所排放氮素气体的组成;对于旱地阶段硝态氮比较丰富的水稻土,避免在淹水前或淹水期间施用有机肥,有利于削减温室气体排放.     

Effects of plant diversity on greenhouse gas emissions in microcosms simulating vertical constructed wetlands with high ammonium loading

Wastewater with relatively high nitrogen concentrations is a major source of nitrous oxide (N₂O) and methane (CH₄) emissions and exerts multiple stresses on the environment. Studies have shown that plant diversity plays an important role in ecosystem functioning. However, the effects of plant species diversity on CH₄ and N₂O emissions under high ammonium (NH₄⁺-N) loading rates remain unclear. In this study, a microcosm experiment simulating vertical constructed wetlands supplied with high NH₄⁺-N water levels was established. The treatments included four species richness levels (1, 2, 3, 4) and 15 species compositions. There was no significant relationship between species richness and N₂O emissions. However, N₂O emissions were significantly reduced by specific plant species composition. Notably, the communities with the presence of Rumex japonicus L. reduced N₂O emissions by 62% compared to communities without this species. This reduction in N₂O emissions may have been a result of decreased N concentrations and increased plant biomass. CH₄ emissions did not respond to plant species richness or species identity. Overall, plant species identity surpassed species richness in lowering N₂O emissions from constructed wetlands with high NH₄⁺-N water. The results also suggest that communities with R. japonicus could achieve higher N removal and lower greenhouse gas emissions than other wetland species.     

Biosphere–atmosphere exchange of reactive nitrogen and greenhouse gases at the NitroEurope core flux measurement sites: Measurement strategy and first data sets

The NitroEurope project aims to improve understanding of the nitrogen (N) cycle at the continental scale and quantify the major fluxes of reactive N by a combination of reactive N measurements and modelling activities. As part of the overall measurement strategy, a network of 13 flux ‘super sites’ (Level-3) has been established, covering European forest, arable, grassland and wetland sites, with the objective of quantifying the N budget at a high spatial resolution and temporal frequency for 4.5 years, and to estimate greenhouse gas budgets (N₂O, CH₄ and CO₂). These sites are supported by a network of low-cost flux measurements (Level-2, 9 sites) and a network to infer reactive N fluxes at 58 sites (Level-1), for comparison with carbon (C) flux measurements.Measurements at the Level-3 sites include high resolution N₂O, NO (also CH₄, CO₂) fluxes, wet and dry N deposition, leaching of N and C and N transformations in plant, litter and soil. Results for the first 11 months (1.8.2006 to 30.6.2007) suggest that the grasslands are the largest source of N₂O, that forests are the largest source of NO and sink of CH₄ and that N deposition rates influence NO and N₂O fluxes in non-agricultural ecosystems. The NO and N₂O emission ratio is influenced by soil type and precipitation. First budgets of reactive N entering and leaving the ecosystem and of net greenhouse gas exchange are outlined. Further information on rates of denitrification to N₂ and biological N₂ fixation is required to complete the N budgets for some sites. The quantitative roles played by CO₂, N₂O and CH₄ in defining net greenhouse gas exchange differ widely between ecosystems depending on the interactions of climate, soil type, land use and management.     

节水灌溉和控释肥施用耦合措施对单季稻田CH4和N2O排放的影响

以我国华东地区典型单季稻水稻田(江苏宜兴)的原柱状土为研究对象,通过两年土柱观测试验,研究不同灌溉管理模式(长期淹水CF、间隙灌溉Ⅱ、控制灌溉CI)和氮肥施用(不施氮CK、尿素Urea和控释肥CRF)耦合措施对水稻生长期内CH4和N2O排放和产量的影响,以期优选典型单季稻田减排增效的水肥管理模式.结果表明,两种节水灌溉方式(CI和Ⅱ)均显著影响稻田土壤CH4和N2O排放量及二者的综合温室效应(GWP)和排放强度(GHGI),与CF相比,Ⅱ和CI均显著提高了 N2O排放量(P＜0.05),降低了 CH4排放量(P＜0.05),进而二者的GWP和GHGI分别显著降低28.9％～71.4％和14.3％～70.4％(P＜0.05);两种节水灌溉模式相比,CI较Ⅱ模式呈现较好的CH4减排优势,排放总量降低了 57.7％～91.8％,而二者的N2O排放量无显著性差异(P＞0.05),最终CI对GWP和GHGI的减排效应略优于Ⅱ模式2.0％～56.2％.施用氮肥(Urea和CRF)均显著促进N2O排放18.4％～2547.8％(P＜0.05),其中CRF处理N2O排放量均略高于Urea处理32.7％～78.6％,但无显著性差异(P＞0.05);CH4排放总量对施氮处理的响应随水分管理模式的不同而不同,总体而言,施用CRF较Urea对稻田土壤GWP和GHGI均无显著影响(P＞0.05).相关分析表明,2018年CF模式的Urea处理和Ⅱ模式的Urea、CRF处理中N2O排放通量与田面水NH4+-N浓度分别呈现显著(P＜0.05)和极显著的正相关关系(P＜0.01),而二者在2019年CI模式的CK和CRF处理中呈现相反规律;2018年CI模式下CK、CRF处理的N2O排放通量与田面水NO3--N浓度呈极显著的正相关关系(P＜0.01).节水灌溉和氮肥施用对水稻产量均呈显著影响(P＜0.05),与CF相比,两种节水灌溉模式(Ⅱ、CI)水稻产量均下降了 14.7％～37.7％;CRF处理较Urea处理略提高水稻产量2.5％～7.4％(P＜0.05).综合考虑稻田土壤GWP、GHGI和水稻产量,节水模式与控释肥施用对稻田土壤减排增产的耦合效应仍有待进一步研究.     

三江平原泥炭沼泽湿地N2O排放通量及影响因子

运用静态暗箱-气相色谱法观测了三江平原毛苔草泥炭沼泽湿地植物生长季N2O排放通量,并分析了其关键影响因子.结果表明:生长季N2O排放通量季节变化动态明显,最大值出现在7月上旬;平均排放通量为76.77μg/(m2·h),高于潜育沼泽湿地[20~60μg/(m2·h), 2002~2005].N2O排放通量与土壤温度存在极显著指数关系(P<0.01),且随土壤深度(土壤10cm以下)的增加相关关系逐渐减弱;与水位呈极显著负相关关系(P<0.01);另外,植被是影响N2O排放的主要生物因子,有植被参与的N2O排放是无植被的1.7倍.总之,水位和土壤温度是控制泥炭沼泽N2O排放呈明显季节变化的主要因素,而土壤水文物理特性的差异是引起泥炭沼泽N2O排放高于潜育沼泽的主要原因.经初步估算,三江平原泥炭沼泽每年植物生长季N2O排放总量约为72.9Mg,表明泥炭沼泽湿地在生长季是重要的N2O潜在排放源.     

生物炭和有机肥对华北农田盐碱土N2O排放的影响

基于山东滨州地区冬小麦-夏玉米轮作大田试验,探究了施用生物炭和有机肥对夏玉米季土壤氧化亚氮(N_2O)排放的影响,为盐碱土壤N_2O增汇减排提供理论依据.试验按照不同处理氮、磷、钾含量相同原则,设置对照CK[N:0.2t·(hm~2·a)~(-1),P_2O_5:0.12 t·(hm~2·a)~(-1),K_2O:0.2 t·(hm~2·a)~(-1)]、C1[5 t·(hm~2·a)~(-1)生物炭]、C2[10 t·(hm~2·a)~(-1)生物炭]、C3[20 t·(hm~2·a)~(-1)生物炭]、M1[7.5 t·(hm~2·a)~(-1)有机肥]、M2[10 t·(hm~2·a)~(-1)有机肥]这6个处理.结果表明,施加生物炭和有机肥对土壤N_2O排放影响趋势基本一致,排放高峰均出现在施肥(基肥和追肥)后,累积排放量占整个生育期排放量的近一半;与CK相比,C1、C2分别降低N_2O排放的45.3%、31.6%,而C3、M1、M2分别增加了17.3%、37.4%、27.6%.施加生物炭和有机肥均会对土壤N_2O排放产生影响,施加生物炭可以降低N_2O排放,而施加有机肥则促进了N_2O排放.因此,生物炭对减少农田N_2O排放具有巨大潜力.     

地膜覆盖和施氮对菜地N2O排放的影响

为了探讨地膜覆盖和不同施氮处理对菜地N_2O排放的影响,以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内辣椒-萝卜轮作菜地为研究对象,采用静态暗箱/气相色谱法,进行为期2 a的田间原位观测.试验设置8个处理,分别为对照常规(NN0)、对照覆膜(FN0),低N常规(NN1)、低N覆膜(FN1),中N常规(NN2)、中N覆膜(FN2),高N常规(NN3)、高N覆膜(FN3),研究地膜覆盖和施氮对菜地N_2O的排放特征和影响因素.结果表明,覆膜与常规两种种植方式对于菜地N_2O的排放体现出明显差异,表现为辣椒季常规显著大于覆膜(P 0. 05),萝卜季为覆膜显著大于常规(P 0. 05). 2014年5月至2016年4月观测期间,覆膜种植下无氮、低氮、中氮和高氮菜地N_2O年均累积排放量分别为244. 91、730. 49、903. 32和1 867. 45 mg·m-2,常规种植下N_2O年均累积排放量为221. 48、840. 33、1 256. 50和1 469. 67 mg·m-2.不同施氮梯度对于菜地N_2O的排放呈现为随施氮量增加N_2O的排放随之增加.通过计算N_2O排放系数可知,覆膜可以一定程度上降低辣椒季N_2O的排放系数,而萝卜季则没有明显规律. 2014年5月至2015年4月,辣椒季常规和覆膜种植下均为低氮菜地的N_2O排放系数最高,在萝卜季则显示为高氮排放系数最高; 2015年5月至2016年4月,则显示辣椒季为高氮菜地N_2O排放系数最高,而萝卜季低氮菜地最高. N_2O的排放通量和土壤氮素含量以及土壤温度呈显著相关关系,而地膜覆盖可一定程度地增加土壤中氮素的含量,进而影响菜地N_2O的排放通量.     

Influence of organic ley–arable management and afforestation in sandy loam to clay loam soils on fluxes of N2O and CH4 in Scotland

Assessment of the sustainability of alternatives to conventional uses of agricultural land, viz. organic systems and afforestation should include consideration of any effects on trace gas budgets. Nitrous oxide (N₂O) and methane (CH₄) fluxes and controlling soil properties were measured in an organic ley–arable rotation in north-east Scotland on a sandy loam. N₂O fluxes were monitored in the ley and arable phases and in organic permanent grass (Lolium perenne) located nearby throughout the 3-year phase duration. Gas fluxes in woodland that had been converted from arable for 1 or 6 years were also measured in both north-east and south-east Scotland on sandy loam to clay loam soils. The climate is maritime and variable with annual rainfall between 800 and 900 mm. Within the organic rotation, differences in N₂O fluxes between the ley and arable phases were less marked than in conventional agriculture. Although this was mainly because grassland emissions were low, some losses from the arable component were also relatively high. Seasonal rainfall had a major influence on cumulative emissions of N₂O, including the first year after conversion from ley to arable. In the short term, changing land use from arable to woodland increased CH₄ oxidation rates and decreased N₂O emissions, though both these rates were also influenced by seasonal weather. Afforestation of agricultural land appears to be more beneficial to trace gas exchange than conversion to organic production.     

Differences in nitrous oxide fluxes from red soil under different land uses in mid-subtropical China

Red soil may play an important role in nitrous oxide (N₂O) emissions due to its recent land use change pattern. To predict the land use change effect on N₂O emissions, we examined the relationship between soil N₂O flux and environmental determinants in four different types of land uses in subtropical red soil. During two years of study (January 2005-January 2007), biweekly N₂O fluxes were measured from 09:00 to 11:00 a.m. using static closed chamber method. Objectives were to estimate the seasonal and annual N₂O flux differences from land use change and, reveal the controlling factors of soil N₂O emission by studying the relationship of dissolved organic carbon (DOC), microbial biomass carbon (MBC), water filled pore space (WFPS) and soil temperature with soil N₂O flux. Nitrous oxide fluxes were significantly higher in hot-humid season than in the cool-dry season. Significant differences in soil N₂O fluxes were observed among four land uses; 2.9, 1.9 and 1.7 times increased N₂O emissions were observed after conventional land use conversion from woodland to paddy, orchard and upland, respectively. The mean annual budgets of N₂O emission were 0.71-2.21 kg N₂O-N ha⁻¹ year⁻¹ from four land use types. The differences were partly attributed to increased fertilizer use in agriculture land uses. In all land uses, N₂O fluxes were positively related to soil temperature and DOC accounting for 22-48% and 30-46% of the seasonal N₂O flux variability, respectively. Nitrous oxide fluxes did significantly correlate with WFPS in orchard and upland only. Nitrous oxide fluxes responded positively to MBC in all land use types except orchard which had the lowest WFPS. We conclude that (1) land use conversion from woodland to agriculture land uses leads to increased soil N₂O fluxes, partly due increased fertilizer use, and (2) irrespective of land use, soil N₂O fluxes are under environmental controls, the main variables being soil temperature and DOC, both of which control the supply of nitrification and denitrification substrates.     

湖南地区不同集约化栽培模式下双季稻稻田CH4和N2O的排放规律

采用静态暗箱-气相色谱法研究了湖南双季稻稻田不施氮(NN)、当地常规(FP)、高产高效(YE)、再高产(HY)、再高效(HE)5种不同栽培模式下温室气体(CH4、N2O)的排放规律.结果表明:水稻生长季CH4累积排放量变化为(206.5±37.5) kg· hm-2(FP,早稻)～(490.5±65.7) kg·hm-2(HE,晚稻),N2O-N累积排放量变化为(0.08±0.05) kg·hm-2(NN,早稻)～(0.326±0.15) kg·hm-2(HY,晚稻).不同栽培模式对CH4和N2O的排放都有显著影响(p＜0.05).HE模式CH4排放显著高于其他模式62％～ 87％(p＜0.05),尤其是晚稻季节;除NN模式外,其他4种模式间N2O排放差异不显著.冬季休闲期也是CH4和N2O排放的重要时期,分别占全年排放量的9.7％～19.7％和42％～ 62％.CH4主导了稻田不同栽培模式下的综合温室效应,在各模式中均占95％以上.施氮肥提高了作物产量,降低了温室气体强度(GHGI).在5种模式中,YE和HY模式温室气体强度较小,HY模式下仅为(0.97±0.16) kg·kg-1(以每kg产量排放的CO2当量计).因此,与FP模式相比,YE和HY模式既能提高产量和氮肥利用率,也能减缓温室效应;但HE模式排放的温室气体较高,在实际应用前尚需进一步研究.     

厌氧条件下砂壤水稻土N2、N2O、NO、CO2和CH4排放特征

了解厌氧条件土壤反硝化气体(N2、N2O和NO)、CO2和CH4排放特征,是认识反硝化过程机制的基础,并有助于制定合理的温室气体减排措施.定量反硝化产物组成,可为氮转化过程模型研发制定正确的关键过程参数选取方法或参数化方案.本研究选取质地相同(砂壤土)的两个水稻土为研究对象,通过添加KNO3和葡萄糖的混合溶液,将培养土壤的初始NO-3和DOC含量分别调节到50 mg·kg-1和300 mg·kg-1,采用氦环境培养-气体及碳氮底物直接同步测定方法,研究完全厌氧条件下土壤N2、N2O、NO、CO2和CH4的排放特征,并获得反硝化气态产物中各组分的比率.结果表明,在整个培养过程中,两个供试土壤的N2、N2O和NO累积排放量分别为6~8、20和15~18 mg·kg-1,这些气体排放量测定结果可回收土壤NO-3变化量的95%~98%,反硝化气态产物以N2O和NO为主,其中3种组分的比率分别为15%~19%(N2)、47%~49%(N2O)和34%~36%(NO);但反硝化气体产物组成的逐日动态均显现为从以NO为主逐渐过渡到以N2O为主,最后才发展到以N2为主.以上结果说明,反硝化气体产物组成是随反硝化进程而变化的,在以气体产物组成比率作为关键参数计算各种反硝化气体产生率或排放率的模型中,很有必要重视这一点.     

Methane and CO2 fluxes from an Indonesian peatland used for sago palm (Metroxylon sagu Rottb.) cultivation: Effects of fertilizer and groundwater level management

Tropical peatland is a vast potential land source for biological production, but peatland is a major natural source of greenhouse gases, especially methane (CH₄). It is important to evaluate the changes in greenhouse gas emissions induced by cultivation practices for sustainable agricultural use of tropical peatland. We investigated the effects of fertilizer application and the groundwater level on CH₄ and carbon dioxide (CO₂) fluxes in an Indonesian peat soil. The crop cultivated was sago palm (Metroxylon sagu Rottb.), which can grow on tropical peat soil without drainage and yield great amounts of starch. CH₄ emission through sago palm plants was first estimated by collecting gas samples immediately after cutting sago suckers using the closed chamber method. The CH₄ fluxes ranged from negative values to 1.0 mg C m⁻² h⁻¹. The mean CH₄ flux from treatment with macroelements (N, P, and K) and microelements (B, Cu, Fe, and Zn) applied at normal rates did not differ significantly from that of the No fertilizer treatment, although increasing the application rates of macroelements or microelements by 10-fold increased the CH₄ flux by a factor of two or three. The relationship between CH₄ flux and the groundwater table was regressed to a logarithmic equation, which indicated that to maintain a small CH₄ flux, the groundwater table should be maintained at <−45 cm. The CO₂ fluxes ranged between 24 and 150 mg C m⁻² h⁻¹, and were not significantly affected by either fertilizer treatments or the groundwater level. The inclusion of sago palm suckers in a chamber increased CH₄ emission from the peat soil significantly. Thus, gas emissions mediated by certain kinds of palm plants should not be disregarded.     

三峡库区消落带N2O排放及其影响因素

为了探讨亚热带水库消落带N_2O的排放规律,选取三峡库区王家沟一典型消落带内3个高程(180、175和155 m)作为研究对象,采用静态暗箱和浮箱法进行了为期2 a的连续观测.175 m和155 m高程位于三峡库区消落带上,而180 m高程作为对照,为永不淹水的陆地.结果表明,各高程处的N_2O排放通量都表现出明显的季节变化,180 m高程处的春季N_2O排放最低;175 m高程在实验观测的第一年表现为单峰型的夏季N_2O排放高峰,次年在三峡水库实现最高蓄水位175 m后,表现为干湿交替和夏季N_2O高排放的双峰型;155 m高程处只呈现为夏季高N_2O排放的单峰态.另外,位于消落带上的175 m和155 m高程均表现为落干期N_2O排放大于淹水期.各高程处N_2O的年累积排放量为175 m(853.92 mg·m-2)180 m(336.69mg·m~(-2))155 m(324.69 mg·m~(-2)),与180 m高程对照相比,表明短期淹水会促进N_2O排放,而长期淹水则会抑制N_2O排放.相关性分析显示,陆地与消落带落干期的N_2O排放与各环境因子间无显著相关性,消落带淹水期排放与水温和风速呈极显著负相关.对影响陆地、消落带淹水期和落干期N_2O排放的因素进行主成分分析可知,消落带淹水期水体中可溶性氮素的分布是影响水面N_2O排放的最主要因素,而消落带落干期及陆地则是受土壤碳氮含量、土壤温度、湿度及pH等因素的共同影响和制约.     

闽江河口短叶茳芏湿地CH4和N2 O排放对氮输入的短期响应

利用静态箱-气相色谱法,研究了氮输入对闽江河口短叶茳芏湿地CH4和N2O排放通量的短期影响.结果表明,高氮输入在不同采样时间均促进了湿地CH4排放,低氮输入在不同时间则具有不同的变化特征.与对照处理相比,低氮和高氮2种处理分别使湿地CH4排放通量增加了-44.35%～1 057.35%和7.15%～667.37%.外源氮输入在24 h内对湿地N2O排放通量具有明显的正激发效应,最高可增加171.60倍和177.79倍,但在8 d后,氮输入对湿地N2O排放的激发效应减弱甚至消失.氮输入在短时间内对湿地土壤Ec、pH和Eh均未产生显著影响.湿地CH4排放通量在对照处理下仅与5 cm Eh存在显著负相关,在低氮处理下仅与10 cm地温呈显著负相关,在高氮处理下则与5 cm Ec、0、5 cm pH以及0、5、10 cm土壤Eh均呈显著相关性,而N2O排放通量在不同处理下与湿地气温、地温、盐度、pH和Eh等环境因子均不存在显著相关性.研究表明,探讨氮输入对湿地温室气体排放的影响应考虑其时间变异性.     

保护性耕作对后茬冬小麦土壤CO2和N2O排放的影响

为研究保护性耕作对后茬冬小麦土壤CO2和N2O排放的影响,在前茬进行常规耕作(T)、免耕(NT)、免耕+秸秆覆盖(NTS)、常规耕作+秸秆施用(TS)这4种处理,采用静态箱-气相色谱法分析土壤CO2和N2O排放通量.结果表明,保护性耕作没有改变后茬土壤CO2和N2O排放的季节性规律,对冬小麦生物量无明显影响;保护性耕作显著减少了土壤CO2和N2O累积排放量.与T相比,TS、NT、NTS的全生育期土壤CO2累积排放量分别降低了5.95%(P=0.132)、12.94%(P=0.007)和13.91%(P=0.004),土壤N2O累积排放量分别减少了31.23%(P=0.000)、61.29%(P=0.000)和33.08%(P=0.000).本研究表明免耕与秸秆施用能减少后茬作物生长季土壤的CO2和N2O排放量.     

Responses of greenhouse gas fluxes to experimental warming in wheat season under conventional tillage and no-tillage fields

Understanding the effects of warming on greenhouse gas(GHG, such as N_2O, CH_4 and CO_2 )feedbacks to climate change represents the major environmental issue. However, little information is available on how warming effects on GHG fluxes in farmland of North China Plain(NCP). An infrared warming simulation experiment was used to assess the responses of N_2O, CH_4 and CO_2 to warming in wheat season of 2012–2014 from conventional tillage(CT) and no-tillage(NT) systems. The results showed that warming increased cumulative N_2O emission by 7.7% in CT but decreased it by 9.7% in NT fields(p 0.05). Cumulative CH_4 uptake and CO_2 emission were increased by 28.7%–51.7% and 6.3%–15.9% in both two tillage systems,respectively(p 0.05). The stepwise regressions relationship between GHG fluxes and soil temperature and soil moisture indicated that the supply soil moisture due to irrigation and precipitation would enhance the positive warming effects on GHG fluxes in two wheat seasons.However, in 2013, the long-term drought stress due to infrared warming and less precipitation decreased N_2O and CO_2 emission in warmed treatments. In contrast, warming during this time increased CH_4 emission from deep soil depth. Across two years wheat seasons, warming significantly decreased by 30.3% and 63.9% sustained-flux global warming potential(SGWP) of N_2O and CH_4 expressed as CO_2 equivalent in CT and NT fields, respectively. However, increase in soil CO_2 emission indicated that future warming projection might provide positive feedback between soil C release and global warming in NCP.