增温和隔离降雨对亚热带森林土壤N2O通量的影响

设置对照(CT)、增温5 ℃(W)、隔离50%降雨(P)和增温5 ℃+隔离50%降雨(WP)4种处理,以相关功能基因作为标志物,研究增温和隔离降雨影响亚热带森林生态系统土壤N₂O通量变化的途径.结果表明: 隔离降雨显著降低了土壤铵态氮浓度;增温显著降低了土壤N₂O通量和土壤反硝化势.增温处理(W)和降雨处理(P)的土壤微生物生物量氮(MBN)均显著低于对照(CT),AOA amoA基因丰度与MBN和铵态氮含量之间呈显著负相关,但与土壤硝化势和土壤N₂O通量没有显著相关性.路径分析显示,反硝化势直接显著影响土壤N₂O通量,而微生物生物量磷(MBP)和增温则通过直接影响反硝化势来间接影响土壤N₂O通量.温度可能是影响亚热带森林土壤N₂O通量的主要驱动因素,全球变暖可能会减少亚热带森林土壤的N₂O排放.     

全球森林土壤N2O排放通量的影响因子

森林生态系统在全球变暖格局下的地位和作用,尤其是土壤氮库对大气氮沉降增加的响应逐渐成为全球变化研究的热点。本文通过对已有文献资料的调研和整理,分析了1984—2009年间全球38个森林土壤N2O排放通量的野外原位观测结果的分布特征,评估了森林土壤N2O年排放累积通量对大气氮素沉降量和水热条件等因子变化的响应。结果表明,全球森林土壤N2O排放通量的平均值为0.47kgN·hm-2·a-1,而且土壤N2O释放通量随着纬度增加逐渐降低。作为一个复杂的生态过程,土壤N2O累积释放量同样受到年均温、年降水量以及土壤属性的显著影响。其中全球森林土壤N2O释放温度敏感性系数(Q10值)约为1.5。另外,森林土壤N2O排放通量也随着氮沉降量的增加而显著增大,大气氮沉降量可解释土壤N2O排放通量在不同区域之间53%的差异;土壤pH、年均温和大气氮沉降量可以解释区域森林土壤N2O排放通量变化的55%。     

氮沉降和施生物质炭对毛竹林土壤N2O通量的影响

本研究于2019年7月-2020年7月在浙江省杭州市典型毛竹林布置野外控制实验,采用静态箱-气相色谱法测定毛竹林土壤N2O通量,分析生物质炭(10 t·hm-2)、氮沉降(60 kg N·hm-2·a-1)、生物质炭+氮沉降混合处理对土壤N2O通量的影响,并探讨了土壤N2O通量与环境因子的关系.结果 表明:与对照相比,...     

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。     

Responses of CO2, N2O and CH4 fluxes between atmosphere and forest soil to changes in multiple environmental conditions

To investigate the effects of multiple environmental conditions on greenhouse gas (CO₂, N₂O, CH₄) fluxes, we transferred three soil monoliths from Masson pine forest (PF) or coniferous and broadleaved mixed forest (MF) at Jigongshan to corresponding forest type at Dinghushan. Greenhouse gas fluxes at the in situ (Jigongshan), transported and ambient (Dinghushan) soil monoliths were measured using static chambers. When the transported soil monoliths experienced the external environmental factors (temperature, precipitation and nitrogen deposition) at Dinghushan, its annual soil CO₂ emissions were 54% in PF and 60% in MF higher than those from the respective in situ treatment. Annual soil N₂O emissions were 45% in PF and 44% in MF higher than those from the respective in situ treatment. There were no significant differences in annual soil CO₂ or N₂O emissions between the transported and ambient treatments. However, annual CH₄ uptake by the transported soil monoliths in PF or MF was not significantly different from that at the respective in situ treatment, and was significantly lower than that at the respective ambient treatment. Therefore, external environmental factors were the major drivers of soil CO₂ and N₂O emissions, while soil was the dominant controller of soil CH₄ uptake. We further tested the results by developing simple empirical models using the observed fluxes of CO₂ and N₂O from the in situ treatment and found that the empirical models can explain about 90% for CO₂ and 40% for N₂O of the observed variations at the transported treatment. Results from this study suggest that the different responses of soil CO₂, N₂O, CH₄ fluxes to changes in multiple environmental conditions need to be considered in global change study.     

双氢胺对土壤裂缝产生过程中N2O释放的影响

模拟稻田土壤在加入不同量的（NH4）2SO4和双氢按（DCD）抑制剂的溶液后先进行淹水培养,然后让土壤自然蒸发变干,直至土壤产生裂缝到裂缝稳定,最后在裂缝稳定后的复水的连续培养试验。通过模拟对土壤进行复杂的、动态的水分含量变化过程中试验,探讨双氢胺抑制剂对其N2O释放的影响。每天监测土体释放的N2O通量,以及渗漏液中溶解的N2O浓度和pH值。这些监测结果表明：在相同的水分管理条件下,土壤中没有氮肥加入,只有DCD加入的A处理释放N2O气体最少,其平均释放通量为340.91μgm^-2h^-1;土壤中有高剂量的氮肥和DCD加入的E处理释放N2O最多,其平均释放通量为9280.23μgm^-2h^-1。裂缝产生稳定后的复水能减少N2O向空气中的释放。渗漏液中的N2O浓度都是过饱和的。当土壤中肥料（NH4）2SO4加入量（每千克土壤中外加N≤3g）相对较少的情况下,DCD抑制剂能抑制裂缝产生过程中的N2O释放;当土壤中肥料（NH4）2SO4加入量（每千克土壤中外加N≥6g）相对较多的情况下,DCD抑制裂缝产生过程中的N2O释放效果不明显。此外还得出（NH4）2SO4和DCD的加入量比是10：1时,其抑制N2O排放的效果比（NH4）2SO4和DCD的加入量比分别是10：1.5和10：2要好。土体释放的N2O通量和渗漏液中溶解的N2O浓度之间不存在相关性,土体释放的N2O通量和渗漏液中的pH值之间也不存在相关性。但是渗漏液中的N：O浓度和pH值之间存在显著的正线性相关关系。     

全球变化对土壤动物多样性的影响

陆地生态系统由地上和地下两部分组成,二者相互作用共同影响生态系统过程和功能.土壤动物在生物地球化学循环方面起着重要作用.随着人们对土壤动物在生态系统过程中重要性的认识,越来越多的研究表明全球变化对土壤动物多样性产生深刻影响.土地利用方式的改变、温度增加和降雨格局的改变能直接影响土壤动物多样性.CO2浓度和氮沉降的增加主要通过影响植物群落结构、组成和化学成分对土壤动物多样性产生间接影响.不同环境因子之间又能相互作用共同影响土壤动物多样性.了解全球变化背景下不同驱动因子及其交互作用对土壤动物多样性的影响,有助于更好地预测未来土壤动物多样性及相关生态学过程的变化.     

外源氮对沼泽湿地CH4和N2O通量的影响

三江平原沼泽湿地受到大气沉降、地表径流、农业排水等外源氮素的输入,对湿地生态系统CH4和N2O通量有重要影响。采用野外原位施肥试验模拟外源氮输入,设0,60,120,240kgN·hm^-24种试验处理,探讨外源氮对沼泽湿地CH4和N2O通量的影响。结果表明,外源氮促进了CH4和N2O排放。与对照处理比较,各施氮水平CH4平均排放通量分别增加了181％,254％和155％,N2O排放通量分别增加了21％,100％和533％。外源氮输入对CH4排放的季节变化形式影响不大,而N2O的季节变化形式随着氮输入表现出波动变化的趋势。不同施氮水平对CH4排放的促进作用与植物生长阶段和产CH4的微生物过程密切相关,N2O排放通量随氮输入量呈指数增加（R^2=0．97,P〈0．01）。外源氮通过影响湿地微生物过程来进一步影响CH4和N2O的排放。     

施氮和降水格局改变对土壤CH4和CO2通量的影响

氮沉降增加和降水格局改变是全球变化的两项重要内容,但是同时考虑上述两因素对温室气体CH4和CO2通量影响的原位双因子模拟研究还相当有限.本研究以长白山温带阔叶红松林土壤为研究对象,采用静态箱法研究了外施氮源(50 kg N·hm-2·a-1)和增减30％降水对土壤CH4和CO2通量的影响.结果表明:施氮能抑制土壤CH4吸收,有时甚至能将土壤对CH4的吸收转为释放,但这种抑制效应只能维持5d左右,且能在一定程度上改变CH4通量和环境因子(温度、土壤pH、粘粒含量)的相关关系.降水改变未能显著影响土壤CH4通量.对CO2通量而言,施氮能降低土壤CO2排放,长白山阔叶红松林连续施氮第4年的平均抑制效应为27.4％.长期连续施氮的平均抑制效应随施氮时间延长而逐渐增大,一定年限后达到最大值.单次施氮的抑制效应随时间延长逐渐减弱,并在1个月的施氮周期末期基本消失.施氮的抑制效应和土壤充水孔隙度(WFPS)呈显著负相关关系,且升温能增强施氮对CO2释放的抑制效应并延长抑制时间.施氮、降水有可能改变土壤呼吸的温度敏感性.本研究表明,长白山森林土壤氮素尚未达到一定阈值,未来氮沉降增加将抑制CO2的释放和CH4的吸收,因此总体来看施氮抑制土壤碳排放.     

全球变化对土壤动物多样性的影

陆地生态系统由地上和地下两部分组成,二者相互作用共同影响生态系统过程和功能.土壤动物在生物地球化学循环方面起着重要作用.随着人们对土壤动物在生态系统过程中重要性的认识,越来越多的研究表明全球变化对土壤动物多样性产生深刻影响.土地利用方式的改变、温度增加和降雨格局的改变能直接影响土壤动物多样性.CO₂浓度和氮沉降的增加主要通过影响植物群落结构、组成和化学成分对土壤动物多样性产生间接影响.不同环境因子之间又能相互作用共同影响土壤动物多样性.了解全球变化背景下不同驱动因子及其交互作用对土壤动物多样性的影响,有助于更好地预测未来土壤动物多样性及相关生态学过程的变化.     

秸秆不同还田方式对棕壤N_2O排放和土壤理化性质的影响

通过田间试验,采用静态箱-气相色谱法研究秸秆炭化还田和直接还田对棕壤旱田氧化亚氮(N2O)排放和相关土壤理化性质的影响。试验设单施化肥(对照CK)、化肥+玉米秸秆直接还田(CS)、化肥+玉米秸秆炭化还田(BC)3个处理,各处理均施用等量化肥。结果表明:(1)各处理土壤N2O排放量差异显著,表现为CKCSBC,BC和CS处理分别比CK降低38.9%和24.0%;(2)BC处理N2O排放强度显著降低,分别比CS和CK处理降低35.0%和39.2%,而CS与CK处理N2O排放强度差异不显著;(3)CS和BC处理均可显著降低土壤容重和氨氧化潜势,增加土壤p H、速效钾和有机碳含量;(4)相关分析结果表明,N2O排放量与土壤温度、土壤容重和氨氧化潜势均呈显著正相关,与土壤p H、硝态氮含量和土壤有机碳含量呈负相关。     

长期施肥对华北典型潮土N分配和N2O排放的影响

利用长期定位肥料试验研究化学肥料N、有机肥料N以及化学肥料N和有机肥料N混合施用对N分配和N2O排放影响。处理包括化学肥料N、P、K的不同组合NPK、NP、NK、PK、全部施用有机肥料N（OM）、一半化学肥料N＋一半有机肥料N（1／2OM）及不施肥（CK）7个处理。结果表明,等N条件下,处理间N2O排放的差异不显著,N2O排放主要发生在玉米生长期。均衡提供N、P和K显著提高土壤N储量,有机肥料N的效果显著高于化学N肥。施肥也影响N的利用效率和N在作物中的分配。均衡的养分供应有利于N在子粒中积累,而养分缺乏的处理,秸秆中N含量相对较高。进入环境的N量以NK最多,1／20M最少。总体而言,施P肥和有机肥可减少N2O的间接排放,提高土壤N素肥力并能获得较高的产量。     

渗滤液负荷和灌溉深度对土壤氧化亚氮与二氧化碳释放的影响

采用预设取样器和静态箱气相色谱法,对渗滤液灌溉条件下,土柱土壤不同深度剖面 N2O的浓度以及N2O和CO2的表面释放通量进行了监测.结果表明: 渗滤液灌溉可促进N2O的生成和释放,灌溉后24 h内土柱N2O的释放通量与表土下10 cm(r=0.944,P< 0.01)、20 cm(r=0.799,P<0.01)、30 cm(r=0.666,P<0.01)和40 cm(r=0.482,P<0.05)处所生成的N2O浓度呈显著相关,且相关程度依次递减.渗滤液灌溉还促进了CO2的释放,但N2O与CO2释放通量之间无显著相关性(P>0.05).渗滤液的灌溉负荷主要决定温室气体释放总量的强弱(N2O和CO2,以CO2当量计),灌溉负荷为6 mm·d-1条件下温室气体释放总量为灌溉负荷2 mm·d-1的3倍多.采用表土下20 cm处灌溉方式可比表土下10 cm处灌溉方式削减47%的温室气体释放总量.渗滤液灌溉土壤14 d内,N2O释放量约占温室气体释放总量的57.0%～91.0%.     

不同氮输入对湿地草甸沼泽土N_2O排放和有机碳矿化的影响

通过室内培养实验,研究了不同氮输入梯度下(N0:0mg·g-1,N1:0.1mg·g-1,N2:0.2mg·g-1,N3:0.5mg·g-1)湿地草甸沼泽土N2O排放和有机碳矿化特征,并分析了土壤微生物量碳、氮变化规律。整个培养期(23d)内,N0、N1、N2和N3处理N2O排放总量分别为91.12、133.02、147.75和303.45μg.kg-1,随氮输入量增大而增大,表明氮输入对N2O排放产生促进作用;氮输入处理的有机碳矿化速率在整个培养期除最后培养阶段外均低于对照,表明氮输入对有机碳矿化有一定的抑制作用;各氮输入处理土壤微生物量碳降低,与对照差异显著(P0.05),但各处理间差异未达到显著水平,土壤微生物量氮随氮输入量增大呈线性增加,各处理间差异显著(P0.05),表明氮输入影响土壤微生物结构和组成,具体影响机理须进一步探讨。     

间作对旱地CO2和N2O排放影响的研究进展

农田温室气体排放是近年来科学界的研究热点,采用合适的种植模式是减少农田温室气体排放的有效途径之一.本文综述了作物间作对旱地土壤CO₂和N₂O排放的影响及机理.合理间作能够提高土壤有机碳(SOC)含量、促进不同作物秸秆向SOC转化、降低SOC矿化速率,从而减少CO₂排放.禾本科与豆科作物间作能够在维持作物产量的情况下,减少化学氮肥投入、土壤有效氮残留及还田秸秆产生的无机氮,降低N₂O排放.间作作物的互作、田间小气候环境的改善也是影响土壤温室气体排放的重要因素.今后,要增加土壤温室气体监测时长并对影响因子进行综合、全面的分析,尤其是从分子水平探究间作模式下土壤微生物对温室气体产生过程的作用机理,为构建环境友好型农业模式提供科学依据.     

三种控释肥在赤红壤中的氧化亚氮排放

采用静态箱收集和对比法,研究了无作物种植条件下包膜与否对高氮、均衡及高钾3种氮磷钾配比复合肥在华南赤红壤发育的菜园土中氧化亚氮(N2O)排放情况.结果表明:肥料氮磷钾配比不同,N2O排放量差异显著,3种类型复合肥N2O累积排放量表现为均衡型≥高氮型＞高钾型;同一类型复合肥,包膜控释能显著降低N2O排放量,包膜控释高氮、均衡及高钾型复合肥N2O排放总量分别为不包膜复合肥N2O排放量的34.4％、30.5％和89.3％;与不包膜相比,复合肥包膜能降低肥料在土壤中的N2O日排放通量,滞后和削减N2O排放高峰,减少土壤氮素损失以及由N2O排放造成的全球增温潜势.     

Effects of three global change drivers on terrestrial C:N:P stoichiometry: a global synthesis

Over the last few decades, there has been an increasing number of controlled‐manipulative experiments to investigate how plants and soils might respond to global change. These experiments typically examined the effects of each of three global change drivers [i.e., nitrogen (N) deposition, warming, and elevated CO₂] on primary productivity and on the biogeochemistry of carbon (C), N, and phosphorus (P) across different terrestrial ecosystems. Here, we capitalize on this large amount of information by performing a comprehensive meta‐analysis (>2000 case studies worldwide) to address how C:N:P stoichiometry of plants, soils, and soil microbial biomass might respond to individual vs. combined effects of the three global change drivers. Our results show that (i) individual effects of N addition and elevated CO₂ on C:N:P stoichiometry are stronger than warming, (ii) combined effects of pairs of global change drivers (e.g., N addition + elevated CO₂, warming + elevated CO₂) on C:N:P stoichiometry were generally weaker than the individual effects of each of these drivers, (iii) additive interactions (i.e., when combined effects are equal to or not significantly different from the sum of individual effects) were more common than synergistic or antagonistic interactions, (iv) C:N:P stoichiometry of soil and soil microbial biomass shows high homeostasis under global change manipulations, and (v) C:N:P responses to global change are strongly affected by ecosystem type, local climate, and experimental conditions. Our study is one of the first to compare individual vs. combined effects of the three global change drivers on terrestrial C:N:P ratios using a large set of data. To further improve our understanding of how ecosystems might respond to future global change, long‐term ecosystem‐scale studies testing multifactor effects on plants and soils are urgently required across different world regions.     

Four years of experimental climate change modifies the microbial drivers of N2O fluxes in an upland grassland ecosystem

Emissions of the trace gas nitrous oxide (N₂O) play an important role for the greenhouse effect and stratospheric ozone depletion, but the impacts of climate change on N₂O fluxes and the underlying microbial drivers remain unclear. The aim of this study was to determine the effects of sustained climate change on field N₂O fluxes and associated microbial enzymatic activities, microbial population abundance and community diversity in an extensively managed, upland grassland. We recorded N₂O fluxes, nitrification and denitrification, microbial population size involved in these processes and community structure of nitrite reducers (nirK) in a grassland exposed for 4 years to elevated atmospheric CO₂ (+200 ppm), elevated temperature (+3.5 °C) and reduction of summer precipitations (?20%) as part of a long‐term, multifactor climate change experiment. Our results showed that both warming and simultaneous application of warming, summer drought and elevated CO₂ had a positive effect on N₂O fluxes, nitrification, N₂O release by denitrification and the population size of N₂O reducers and NH₄ oxidizers. In situ N₂O fluxes showed a stronger correlation with microbial population size under warmed conditions compared with the control site. Specific lineages of nirK denitrifier communities responded significantly to temperature. In addition, nirK community composition showed significant changes in response to drought. Path analysis explained more than 85% of in situ N₂O fluxes variance by soil temperature, denitrification activity and specific denitrifying lineages. Overall, our study underlines that climate‐induced changes in grassland N₂O emissions reflect climate‐induced changes in microbial community structure, which in turn modify microbial processes.     

Evaluation of photoacoustic infrared spectroscopy for simultaneous measurement of N2O and CO2 gas concentrations and fluxes at the soil surface

Simultaneous measurement of N₂O and CO₂ flux at the soil surface with photoacoustic infrared spectroscopy (PAS) is gaining popularity due to portability, low maintenance, and ease‐of‐operation. However, the ability of PAS to measure N₂O with accuracy and precision similar to gas chromatography (GC) is uncertain due to overlap in N₂O, CO₂, and H₂O absorbance spectra combined with the large range in analyte concentrations. We tested the ability of six PAS units to simultaneously measure N₂O and CO₂ gas concentrations and fluxes with accuracy and precision similar to two GC units. We also evaluated H₂O vapor and CO₂ interferences with N₂O measurement. The accuracy and precision of standard gas concentration measurements with PAS and GC were similar. High water vapor (~26 600 ppm) and CO₂ concentrations (~4500 ppm) did not interfere with N₂O measurement across the concentration range typically observed in static flux chambers at the soil surface (~0.5–3.0 ppm N₂O). On average, N₂O fluxes measured with the six PAS were 4.7% higher than one GC and 9.9% lower than the second GC.     

降雨和土壤湿度对贵州旱田土壤N2O释放的影响

以南方亚热带代表性旱田土壤-贵州玉米-油菜轮作田、大豆-冬小麦轮作田和休耕地为观测对象,研究土壤N2O释放通量季节变化与降雨和土壤湿度的关系,同时,采用DNDC模型定量探讨了未来降雨量变化对土壤N2O释放的潜在影响,结果表明,降雨与N2O释放峰间存在明显的驱动-响应关系,N2O释放通量与降雨量和土壤湿度间存在正相关性,模型检验结果表明,夏秋季土壤N2O释放通量与降雨量变化呈正相关,而降雨量的大幅度增加或下降将引起冬春季土壤N2O释放通量的微弱下降。