剔除林下灌草和添加翅荚决明对尾叶桉林土壤温室气体排放的影响

森林土壤是CO₂、CH₄和N₂O等温室气体的重要排放源。采用静态箱/色谱分析技术对中国科学院鹤山丘陵综合开放试验站的尾叶桉(Eucalyptus urophylla)林土壤CO₂、CH₄和N₂O排放通量进行了原位测定, 研究剔除林下灌草和添加翅荚决明(Cassia alata)对尾叶桉林土壤温室气体排放的影响。结果表明: 尾叶桉林土壤CO₂排放通量在湿季维持在较高水平, 在旱季则明显降低。CH₄和N₂O在湿季波动幅度较大, 在旱季则相对稳定。土壤CO₂和CH₄通量峰值均出现在湿季, 但N₂O峰值出现在旱季的12月。尾叶桉林土壤在不同处理下可能是CH₄的源, 也可能是CH₄的汇, 而对于CO₂和N₂O则主要是源。尾叶桉林下剔除灌草及添加翅荚决明能显著增大土壤CO₂和N₂O的排放, 但林下灌草剔除后有利于CH₄的吸收, 添加翅荚决明有利于CH₄的排放。表层土壤温度和湿度是影响土壤温室气体排放的首要因子。呼吸底物(氮源)和土壤微生物量也是影响土壤温室气体排放的重要因子。     

模拟增温对荒漠生物土壤结皮-土壤系统CO2、CH4和N2O通量的影响

目前, 有关增温条件下荒漠生物土壤结皮(BSCs)-土壤系统与大气之间主要温室气体(CO₂、CH₄和N₂O)通量变化的研究十分匮乏, 以致很难准确地评估荒漠生态系统温室气体通量对气候变暖的响应与反馈的方向和程度。该文选择腾格里沙漠东南缘天然植被区由藻类、藓类以及二者混生的3种类型的BSCs覆盖土壤为研究对象, 以开顶式生长室(OTC)为增温方式模拟全球变暖, 采用静态箱-气相色谱法探究了2012年7月至2013年6月增温和不增温处理下CO₂、CH₄和N₂O通量的变化特征。结果表明: 增温和结皮类型对CO₂、CH₄和N₂O通量没有显著影响。采样日期、结皮类型与采样日期, 以及增温与结皮类型和采样日期的互作显著影响CO₂和CH₄通量, 增温和采样日期互作显著影响CH₄通量。BSCs-土壤系统的CO₂、CH₄和N₂O年通量及其增温潜能在增温和不增温处理下的差异均不显著。CO₂通量与5 cm深度的土壤温度呈显著的指数正相关关系, 与10 cm深度的土壤湿度呈线性正相关关系; 藓类、混生结皮的CH₄通量与5 cm深度的土壤温度和10 cm深度的土壤湿度均呈显著的线性负相关关系; 3种结皮类型的N₂O通量与5 cm深度的土壤温度均无相关关系, 藓类结皮的N₂O通量与10 cm深度的土壤湿度呈显著的线性负相关关系。藓类结皮的CO₂和CH₄在增温和不增温两种处理下的通量差异与5 cm深度的土壤温度差异呈显著的负线性相关, 藻类结皮N₂O的通量差异与温度差异呈近似正相关关系(p = 0.051)。以上结果说明: 在全球变暖的背景下, 荒漠BSCs-土壤系统主要温室气体通量不会有明显的变化, 意味着荒漠生态系统温室气体的排放可能对气候变暖没有明显的 反馈。     

剔除灌草和添加翅荚决明对厚荚相思林土壤温室气体排放的影响

森林土壤是CO₂、CH₄和N₂O等温室气体的主要排放源.本研究采用静态箱/色谱分析技术,对中国科学院鹤山丘陵综合开放试验站内厚荚相思林土壤CO₂、CH₄和N₂O通量进行原位测定,研究剔除林下灌草和添加翅荚决明对土壤温室气体排放的影响.结果表明：厚荚相思林土壤CO₂通量在湿季维持较高水平,在旱季则明显降低.CH₄和N₂O在9-11月波动幅度较大,峰值出现在10月.在不同处理下,厚荚相思林土壤可能是CH₄的源也可能是CH₄的汇,而于CO₂和N₂O则是源.林下剔除灌草能显著增大土壤CO₂排放(P<0.05),而添加翅荚决明能加快土壤CH₄的排放(P<0.05).林下剔除灌草及添加翅荚决明两种处理都能够加大N₂O的排放通量.表层土壤温度、湿度、NO₃^--N和微生物生物量碳都是影响土壤温室气体排放的重要因子.     

大兴安岭重度火烧迹地天然次生林土壤温室气体通量及其影响因子

为研究大兴安岭重度火烧迹地自然恢复后的林分土壤温室气体源汇强度及其影响因素,采用静态箱/气相色谱法,对生长季(6—9月)天然次生林土壤温室气体CO₂、CH₄、N₂O通量进行原位观测.结果表明: 1)生长季内天然次生林土壤为大气CO₂、N₂O的源,CH₄的汇,平均通量分别为575.81 mg·m^-2·h^-1、17.81 μg·m^-2·h^-1和-68.69 μg·m^-2·h^-1;CO₂与CH₄通量在生长季内表现出明显的双峰变化规律,N₂O通量则呈单峰变化,且均在8月达到观测期的最大值.2)土壤温度是影响该区天然次生林土壤温室气体通量的主控因子,土壤湿度和大气湿度在昼夜与季节尺度上与土壤温室气体通量的相关性不同.3)该区天然次生林9:00—12:00时段观测获得的土壤气体通量值经矫正后可代表当日气体通量.研究补充了大兴安岭火烧迹地森林生态系统温室气体通量数据,为该区土壤温室气体源汇的相关研究提供了依据.     

透光抚育对温带帽儿山红松林非生长季土壤温室气体排放的影响

非生长季土壤温室气体排放在碳氮循环中具有重要作用,而采伐干扰对非生长季森林土壤温室气体排放具有何种影响并不明确.采用静态暗箱-气相色谱法,同步观测温带帽儿山50年生红松人工林在不同透光抚育方式下(次生林冠下栽植红松10年时设立为对照;半透光抚育: 伐除上层林木50%;全透光抚育: 伐除上层林木100%)非生长季土壤3种温室气体(CO₂、CH₄和N₂O)排放通量及其相关环境因子(土壤温度、含水量及碳氮含量等),研究采伐干扰对非生长季森林土壤温室气体排放的影响及主控因子.结果表明: 透光抚育会降低非生长季土壤CO₂、CH₄和N₂O的排放通量,全透光和半透光抚育显著降低了温带红松林非生长季土壤CO₂排放量21.0%和22.8%,并降低CH₄吸收量16.0%和16.4%,但差异不显著,全透光抚育显著降低N₂O排放量23.5%,而半透光抚育降低11.2%且差异不显著.温带红松林非生长季土壤CO₂、CH₄和N₂O的年贡献率分别为11.7%～14.2%、13.1%～17.0%和63.9%～72.6%,透光抚育降低了非生长季土壤CO₂(1.4%～2.5%)和CH₄(0.7%～3.9%)年贡献率,但提高了N₂O年贡献率(2.4%～8.7%).透光抚育增加了CO₂排放与土壤温度、含水量、硝态氮及铵态氮的相关性,降低其与有机碳的相关性,增加了CH₄排放与土壤含水量、酸碱度、有机碳和铵态氮的相关性,降低其与硝态氮的相关性,增加了N₂O排放与土壤温度相关性,降低其与硝态氮和铵态氮的相关性,改变了其与土壤酸碱度的正负相关关系.因此,透光抚育经营方式能够显著影响温带森林非生长季土壤温室气体排放,其中全透光抚育降低非生长季土壤N₂O排放能力要强于半透光抚育.     

加气灌溉对不同施氮水平的设施甜瓜土壤CO2和N2O排放的影响

为探讨不同加气灌溉施氮模式下设施甜瓜土壤CO₂和N₂O排放的动态变化规律及其与土壤温度、湿度的关系,本研究采用密闭静态箱-气相色谱法对加气灌溉不同施氮水平下土壤CO₂和N₂O排放进行监测,并分析了加气灌溉对不同施氮量下土壤CO₂和N₂O排放的影响.试验采用加气灌溉(AI)和不加气灌溉(CK)两种灌溉方式,施氮量设不施氮(N₁)、传统施氮量的2/3(150 kg·hm^-2,N₂)和传统施氮量(225 kg·hm^-2,N₃)3个施氮水平.结果表明:加气灌溉土壤CO₂和N₂O排放量高于不加气灌溉处理,但是差异不显著;相同灌溉模式下,CO₂和N₂O排放量随施氮量的增加而显著增加,施氮量是土壤CO₂和N₂O排放的主要影响因素.加气灌溉条件下,不同施氮处理N₂O排放通量与土壤温度和湿度呈显著正相关,CO₂排放通量与土壤温度呈显著正相关.加气减氮处理在氮肥减少1/3的情况下,甜瓜产量提高了6.9%,温室气体排放引起的增温潜势值从9544.82 kg·hm^-2下降到9340.72 kg·hm^-2.综上,通过加气灌溉减少氮肥施用量来抑制农业生产系统中温室气体排放是可行的.     

加气灌溉对不同施氮水平的设施甜瓜土壤CO2和N2O排放的影响

为探讨不同加气灌溉施氮模式下设施甜瓜土壤CO₂和N₂O排放的动态变化规律及其与土壤温度、湿度的关系,本研究采用密闭静态箱-气相色谱法对加气灌溉不同施氮水平下土壤CO₂和N₂O排放进行监测,并分析了加气灌溉对不同施氮量下土壤CO₂和N₂O排放的影响.试验采用加气灌溉(AI)和不加气灌溉(CK)两种灌溉方式,施氮量设不施氮(N₁)、传统施氮量的2/3(150 kg·hm^-2,N₂)和传统施氮量(225 kg·hm^-2,N₃)3个施氮水平.结果表明:加气灌溉土壤CO₂和N₂O排放量高于不加气灌溉处理,但是差异不显著;相同灌溉模式下,CO₂和N₂O排放量随施氮量的增加而显著增加,施氮量是土壤CO₂和N₂O排放的主要影响因素.加气灌溉条件下,不同施氮处理N₂O排放通量与土壤温度和湿度呈显著正相关,CO₂排放通量与土壤温度呈显著正相关.加气减氮处理在氮肥减少1/3的情况下,甜瓜产量提高了6.9%,温室气体排放引起的增温潜势值从9544.82 kg·hm^-2下降到9340.72 kg·hm^-2.综上,通过加气灌溉减少氮肥施用量来抑制农业生产系统中温室气体排放是可行的.     

科尔沁沙丘-草甸梯级生态系统土壤温室气体通量特征及其影响因素

采用静态箱-气相色谱法,对科尔沁半干旱地区典型的沙丘-草甸梯级生态系统中半流动沙丘和草甸湿地的温室气体(CO₂、CH₄、N₂O)通量进行了观测,分析了生长季温室气体的动态变化及其与环境影响因子的关系.结果表明: 生长季半流动沙丘和草甸湿地CH₄通量均整体表现为吸收,平均值分别为-52.7和-34.7 μg·m^-2·h^-1,介于-176.1～49.8 μg·m^-2·h^-1之间变化,8月22日半流动沙丘CH₄吸收值达到生长季最大值;8、9月降雨集中时段内草甸湿地CH₄通量表现为持续排放,与半流动沙丘呈明显差异.N₂O通量在7月21日达到生长季最大值,半流动沙丘N₂O通量的月均值表现为7月>8月>9月>6月>5月.土壤温湿度是影响CO₂和CH₄通量的关键因子,N₂O通量主要受土壤温度的影响.样地土壤温度敏感性(Q₁₀)表现为半流动沙丘(1.009)<草甸湿地(1.474),半流动沙丘土壤受到水分胁迫,导致其温室气体通量对土壤温度变化的敏感性明显低于草甸湿地.     

天目山常绿落叶阔叶混交林土壤温室气体排放特点

采用静态箱-气象色谱法, 将试验样地按照自上而下分为A、B、C、D 四个梯度的采样点。研究了浙江天目山常绿落叶阔叶混交林2013 年3 月-11 月期间土壤温室气体排放的时空变化特点, 并分析了不同梯度的土壤温湿度与气体排放通量的相关性。结果表明: (1)天目山常绿落叶阔叶混交林土壤CO₂ 和CH₄ 两种温室气体排放/吸收季节变化特征较一致, 即夏季>春季>秋季; N₂O 排放通量季节变化表现为夏季>秋季>春季。其中, CO₂ 和N₂O 表现为土壤的排放源, CH₄ 为大气的吸收汇。(2)空间上, CO₂ 通量大小表现为: D 采样点> A 采样点> C 采样点 > B 采样点; 土壤对CH4吸收速率表现为A 采样点 > C 采样点 > B 采样点 > D 采样点; 土壤N₂O 通量大小依次为: A 采样点 > C 采样点 > B采样点 > D 采样点。(3)温度是影响天目山常绿落叶阔叶混交林土壤CO₂ 通量重要因子; CH₄ 的吸收通量随温度的升高和湿度的降低而增大; 在海拔较低的地区, 温度是N₂O 通量的重要影响因子, 海拔较高地区, 湿度是N₂O 通量的重要限制因子。     

灌水量对温室番茄土壤CO2、N2O和CH4排放的影响

为揭示不同灌水量对温室番茄土壤CO₂、N₂O和CH₄排放及作物产量的影响,提出有效的减排措施,试验设置充分灌溉(1.0W,W_1.0;W为充分供水的灌水量)、亏缺20%灌溉(0.8W,W_0.8)和亏缺40%灌溉(0.6W,W_0.6)3个灌水水平,采用静态暗箱/气相色谱法于2017年4—12月对两茬温室番茄土壤CO₂、N₂O和CH₄进行全生长季监测,分析土壤CO₂、N₂O和CH₄排放对不同灌水量的响应.结果表明: 番茄两个生长季中,土壤CO₂、N₂O和CH₄排放量均随着灌水量增加呈现逐渐增加的趋势(W_1.0＞W_0.8＞W_0.6),除W_0.6和W_1.0处理间土壤N₂O排放具有显著差异外,其他各处理间气体排放差异均不显著.与W_1.0处理相比,W_0.6和W_0.8处理土壤CO₂排放分别减小了12.2%和8.3%,N₂O分别减小了19.1%和8.0%,CH₄分别减小了11.0%和6.2%.番茄产量和由土壤N₂O和CH₄引起的全球增温潜势(GWP)均随灌水量增加而增加;与W_1.0处理相比,W_0.6处理产量和GWP显著减小,降幅分别为17.0%和22.9%,而W_0.8处理对两者未产生显著影响.单位产量GWP随灌水量增加表现为先增加后降低的趋势(W_0.8＞W_1.0＞W_0.6),处理间差异不显著.灌溉水利用效率(IWUE)随灌水量增加而降低,与W_1.0处理相比,W_0.6和W_0.8处理IWUE分别增加了38.3%和9.4%.回归分析表明,土壤CO₂排放通量与土壤水分呈指数负相关关系;土壤CH₄通量与土壤水分呈线性正相关关系;当土壤温度小于18 ℃和大于18 ℃时,土壤N₂O排放通量与土壤温度间均呈指数负相关关系.灌水增加了番茄产量和温室气体排放,但降低了IWUE.综合考虑番茄产量、IWUE和温室效应,推荐W_0.8处理为较佳的灌溉模式.     

Greenhouse gas fluxes of typical northern subtropical forest soils: Impacts of land use change and reduced precipitation

Aims It is important to study the effects of land use change and reduced precipitation on greenhouse gas fluxes (CO₂, CH₄ and N₂O) of forest soils. Methods The fluxes of CO₂, CH₄ and N₂O and their responses to environmental factors of primary forest soil, secondary forest soil and artificial forest soil under a reduced precipitation regime were explored using the static chamber and gas chromatography methods during the period from January to December in 2014. Important findings Results indicate that CH₄ uptake of primary forest soil ((-44.43 ± 8.73) μg C·m^-2·h^-1) was significantly higher than that of the secondary forest soil ((-21.64 ± 4.86) μg C·m^-2·h^-1) and the artificial forest soil ((-10.52 ± 2.11) μg C·m^-2·h^-1). CH₄ uptake of the secondary forest soil ((-21.64 ± 4.86) μg C·m^-2·h^-1) was significantly higher than that of the artificial forest ((-10.52 ± 2.11) μg C·m^-2·h^-1). CO₂ emissions of the artificial forest soil ((106.53 ± 19.33) μg C·m^-2·h^-1) were significantly higher than that of the primary forest soil ((49.50 ± 8.16) μg C·m^-2·h^-1) and the secondary forest soil ((63.50 ± 5.35) μg C·m^-2·h^-1) (p < 0.01). N₂O emissions of the secondary forest soil ((1.91 ± 1.22) μg N·m^-2·h^-1) were higher than that of the primary forest soil ((1.40 ± 0.28) μg N·m^-2·h^-1) and the artificial forest soil ((1.01 ± 0.86) μg N·m^-2·h^-1). Reduced precipitation (-50%) had a significant inhibitory effect on CH₄ uptake of the artificial forest soil, while it enhanced CO₂ emissions of the primary forest soil and the secondary forest soil. Reduced precipitation had a significant inhibitory effect on CO₂ emissions of the artificial forest soil and N₂O emissions of the secondary forest (p < 0.01). Reduced precipitation promotes N₂O emissions of the primary forest soil and the artificial forest soil. CH₄ uptake of the primary forest and the secondary forest soil increased significantly with the increase of soil temperature under natural and reduced precipitation. CO₂ and N₂O emission fluxes of the primary forest soil, secondary forest soil and artificial forest soil were positively correlated with soil temperature (p < 0.05). Soil moisture inhibited CH₄ uptake of the secondary forest soil and the artificial forest soil (p < 0.05). CO₂ emissions of the primary forest soil were significantly positively correlated with soil moisture (p < 0.05). N₂O emissions of primary forest soil and secondary forest soil were significantly correlated with the nitrate nitrogen content (p < 0.05). It was implied that reduced precipitation and land use change would have significant effects on greenhouse gas emissions of subtropical forest soils.     

Effluxes of nitrous oxide,methane and carbon dioxide and their responses to increasing nitrogen deposition in the Gurbantünggüt Desert of Xinjiang,China

Aims Desert soils play an important role in the exchange of major greenhouse gas (GHG) between atmosphere and soil. However, many uncertainties existed in understanding of desert soil role, especially in efflux evaluation under a changing environment. Methods We conducted plot-based field study in center of the Gurbantünggüt Desert, Xinjiang, and applied six rates of simulated nitrogen (N) deposition on the plots, i.e. 0 (N0), 0.5 (N0.5), 1.0 (N1), 3.0 (N3), 6.0 (N6) and 24.0 (N24) g·m^-2·a^-1. The exchange rates of N₂O, CH₄ and CO₂ during two growing seasons were measured for two years after N applications. Important findings The average efflux of two growing seasons from control plots (N0) were 4.8 μg·m^-2·h^-1, -30.5 μg·m^-2·h^-1 and 46.7 mg·m^-2·h^-1 for N₂O, CH₄ and CO_2, respectively. The effluxes varied significantly among seasons. N0, N0.5 and N1 showed similar exchange of N₂O in spring and summer, which was relatively higher than in autumn, while the rates of N₂O in N6 and N24 were controled by time points of N applications. The uptake of CH₄ was relatively higher in both spring and summer, and lower in autumn. Emission of CO₂ changed minor from spring to summer, and greatly decreased in autumn in the first measured year. In the second year, the emission patterns were changed by rates of N added. N additions generally stimulated the emission of N₂O, while the effects varied in different seasons and years. In addition, no obvious trends were found in the emission factor of N₂O. The uptake of CH₄ was not significantly affected by N additions. N additions did not change CO₂ emissions in the first year, while high N significantly reduced the CO₂ emissions in spring and summer of the second year, without affected in autumn. Structure equation model analysis on the factors suggested that N₂O, CH₄ and CO₂ were dominantly affected by the N application rates, soil temperature or moisture and plant density, respectively. Over the growing seasons, both the net efflux and the global warming potential caused by N additions were small.     

库布齐沙漠东部不同生物结皮发育阶段土壤温室气体通量

以流动沙地为对照,采用时空替代法分析库布齐沙漠东部固定沙地上不同发育阶段生物结皮藻类结皮和地衣结皮土壤温室气体通量特征及其与环境因子之间的关系,研究生物结皮发育对荒漠土壤温室气体通量的影响.结果表明: 荒漠土壤CO₂排放通量大小为地衣结皮(128.5 mg·m^-2·h^-1)>藻结皮(70.2 mg·m^-2·h^-1)>流动沙地(48.2 mg·m^-2·h^-1),CH₄吸收通量大小为地衣结皮(30.4 μg·m^-2·h^-1)>藻结皮(21.2 μg·m^-2·h^-1)>流动沙地(18.2 μg·m^-2·h^-1),N₂O排放通量大小为地衣结皮(6.6 μg·m^-2·h^-1)>藻结皮(5.4 μg·m^-2·h^-1)>流动沙地(2.5 μg·m^-2·h^-1).CO₂排放具有明显的季节变化,生长季显著大于非生长季;CH₄和N₂O季节变化差异不显著,前者生长季吸收大于非生长季,后者非生长季排放大于生长季.土壤有机碳和全氮含量、土壤微生物数量均是影响温室气体通量的重要因素,环境水热因子是影响土壤CO₂排放的关键因子,但CH₄和N₂O通量对水热因子的变化不敏感.随着植被恢复和生物结皮发育,荒漠土壤温室气体累积通量的不断增大导致其百年尺度的全球增温潜势亦显著提高,依次为地衣结皮(1135.7 g CO₂-e·m^-2·a^-1)>藻结皮(626.5 g CO₂-e·m^-2·a^-1) >流动沙地(422.7 g CO₂-e·m^-2·a^-1).     

长白山北坡不同土壤N2O和CH4排放的初步研究

用箱法技术原位测定了长白山北坡不同土壤(苔原土、生草森林土、棕色针叶林土和暗棕色森林土)6-8月间的N₂O和CH₄排放。结果表明,这些土壤既是N₂O的源,又同时是CH₄的汇。N₂O通量变化于6.17-12.33μg·m^-2·h^-3之间(平均9.37μg·m^-2·h^-1),CH₄通量为-85.63—7.58μg·m^-2·h^-1(平均-41.45μg·m^-3·h^-1),并观察到在N₂O排放和CH₄吸收之间有着相互消长关系。实验室培养实验表明,最大反硝化作用活性存在于土壤上层(0-6cm);不同土壤的反硝化作用活性明显不同。山地暗棕色森林土的CH₄吸收作用也主要发生在土壤的上层(0-12cm).     

Responses of soil respiration with biocrust cover to water and temperature in the southeastern edge of Tengger Desert,Northwest China

Aims Soil respiration of the lands covered by biocrusts is an important component in the carbon cycle of arid, semi-arid and dry-subhumid ecosystems (drylands hereafter), and one of the key processes in the carbon cycle of drylands. However, the responses of the rate of soil respiration with biocrusts to water and temperature are uncertain in the investigations of the effects of experimental warming and precipitation patterns on CO₂ fluxes in biocrust dominated ecosystems. The objectives of this study were to investigate the relationships of carbon release from the biocrust-soil systems with water and temperature in drylands. Methods Intact soil columns with two types of biocrusts, including moss and algae-lichen crusts, were collected in a natural vegetation area in the southeastern fringe of the Tengger Desert. Open top chambers were used to simulate climate warming, and the soil respiration rate was measured under warming and non-warming treatments using an automated soil respiration system (LI-8150). Important findings Over the whole observational period (from April 2016 to July 2016), soil respiration rates varied from -0.16 to 4.69 μmol·m^-2·s^-1 for the moss crust-covered soils and from -0.21 to 5.72 μmol·m^-2·s^-1 for the algae-lichen crust-covered soils, respectively, under different rainfall events (the precipitations between 0.3-30.0 mm). The mean soil respiration rate of the moss crust-covered soils is 1.09 μmol·m^-2·s^-1, which is higher than that of the algae-lichen crust-covered soils of 0.94 μmol·m^-2·s^-1. The soil respiration rate of the two types of biocrust-covered soils showed different dynamics and spatial heterogeneities with rainfall events, and were positively correlated with precipitation. The mean soil respiration rate of the biocrust-covered soils without warming was 1.24 μmol·m^-2·s^-1, significantly higher than that with warming treatments of 0.79 μmol·m^-2·s^-1 (p < 0.05). By increasing the evaporation of soil moisture, the simulated warming impeded soil respiration. In most cases, soil temperature and soil respiration rate displayed a similar single-peak curve during the diel cycle. Our results show an approximately two hours’ lag between soil temperature at 5 cm depth and the soil respiration rate of the biocrust-covered soils during the diel cycle.     

若尔盖高原湿地不同微地貌区甲烷排放通量特征

若尔盖高原是我国泥炭沼泽湿地的主要分布区、青藏高原的主要甲烷(CH₄)排放中心。为了研究湿地微地貌环境对高原湿地CH₄排放通量的影响, 2014年5-10月, 采用静态箱和快速温室气体分析仪原位测量若尔盖高原湖滨湿地3种泥炭沼泽5种微地貌环境下的CH₄排放通量特征。结果表明: (1)常年性淹水泥炭湿地洼地(P-hollow)和草丘(P-hummock)生长季平均CH₄排放通量为68.48和40.32 mg·m^-2·h^-1, 季节性淹水的泥炭湿地洼地(S-hollow)和草丘(S-hummock)平均CH₄排放通量为2.38和0.63 mg·m^-2·h^-1, 而无淹水平坦地(Lawn)平均CH₄排放通量为3.68 mg·m^-2·h^-1; (2)湿地5种微地貌区CH₄排放通量为(23.10 ± 30.28) mg·m^-2·h^-1 (平均值±标准偏差)), 变异系数为131%。分析显示这5种微地貌区CH₄排放通量的平均值与其水位深度平均值存在显著的线性正相关关系(R² = 0.919, p < 0.01), 表明水位深度是控制湿地微地貌区CH₄排放通量空间变化的主要因子; (3) P-hummock、P-hollow和S-hummock的CH₄排放通量存在显著的季节变化, Lawn和S-hollow无明显的季节性变化, 但5种微地貌区在夏季或秋季均观测到CH₄排放通量峰值, 其影响因子可能与水位深度、土壤温度和凋落物输入密切相关; (4) P-hollow可能时常发生冒泡式CH₄排放, 这可能导致过去低估了若尔盖高原湿地的CH₄排放量。     

稻田CH4和N2O的排放及养萍和施肥的影响

用箱法对我国东北稻田CH₄和N₂O排放进行观测研究表明,东北稻田的CH₄排放通量比南方稻田小,平均日排放通量和生长季节排放总量分别为0.07和7.4g·m^-2.稻田淹水期几乎没有N₂O的净排放,但在非淹水期内却有大量N₂O排放(平均通量59μgN₂O·m^-2·h^-1).稻田养萍和施肥明显促进CH₄和N₂O排放。稻田CH₄和N₂O排放之间存在消长关系。制定稻田温室气体减排技术措施时应充分注意这一关系。     

Characteristics of methane emission fluxes in the Zoigê Plateau wetland on microtopography

AimsThe Zoigê Plateau, as a very important wetland distribution region of China, was the major methane (CH₄) emission center of the Qinghai-Xizang Plateau. The objective of this study is to study the effects of microtopographic changes on CH₄ emission fluxes from five plots across three marshes in the littoral zone of the Zoigê Plateau wetland.
Methods CH₄ emission fluxes were measured in five plots across three marshes in Zoigê Plateau wetland using the closed chamber method and Fast Greenhouse Gas Analyzer from May to October in 2014.
Important findings During the growing season, mean CH₄ emission fluxes from the permanently flooded hollow (P-hollow) and hummock (P-hummock) in the Zoigê Plateau wetland were 68.48 and 40.32 mg·m^-2·h^-1, while mean CH₄ emission fluxes from the seasonally flooded hollow (S-hollow) and hummock (S-hummock) were 2.38 and 0.63 mg·m^-2·h^-1. CH₄ emission fluxes from non-flooded lawn was 3.68 mg·m^-2·h^-1. Mean CH₄ emission fluxes from five plots across three sites was 23.10 mg·m^-2·h^-1, with a standard deviation of 30.28 mg·m^-2·h^-1 and the coefficient of variation was 131%. We also found that there was a significant and positive correlation between mean CH₄ emission fluxes and mean water table depth in the five plots across three sites (R² = 0.919, p < 0.01), indicating that water table depth was controlling the spatial variability of CH₄ emission fluxes from the Zoigê Plateau wetland on microtopography. CH₄ emission fluxes in the P-hollow, P-hummock, and S-hummock showed an obvious seasonal pattern, which was not observed in the lawn and S-hollow. However, CH₄ emission peaks were observed in all the plots during summer and/or autumn, which could be closely related to the water table depth, soil temperature, and the magnitude of litter mass. In addition, we found that the CH₄ emission flux in the P-hollow was much higher than the other four plots in the Zoigê Plateau wetland, suggesting that CH₄ in the P-hollow could be often transported to the surface by ebullition and CH₄ emission from the Zoigê Plateau wetland may be under estimated in the past.     

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N₂O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1.763、2.84和0.36mg·m^-2·h^-1,而N₂O的平均排放通量分别为6.74、11.69和55.07μgN₂O-N·m^-2·h^-1,表明稻田连续淹水显著增加CH₄的排放而降低N₂O的排放。水旱轮作降低CH₄排放而提高N₂O的排放,说明稻田CH₄和N₂O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。