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。     

植物与温室气体

CO_2、CH_4和N_2O是3种重要的温室气体由于它们对全球变暖具有较大影响,已引起科学家的广泛关注。研究表明导致温室气体增加的主要原因是人类活动和生物产生,作为占地球生物量约99%的植物,在温室气体产生与消耗中起着怎样的作用,对这一问题的研究将有助于进一步认识植物与大气的生态关系以及在全球气候变化中的作用。目前研究证明植物能吸收大气CO_2,参与大气CH_4和N_2O的产生或排放,因此,它对温室效应的影响是双重的。     

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.     

北亚热带地带性森林土壤温室气体通量对土地利用方式改变和降水减少的响应

弄清土地利用和降水变化对林地土壤主要温室气体(CO₂、CH₄和N₂O)排放通量变化的影响, 是准确评估森林土壤温室气体排放能力的重要基础。该研究以常绿落叶阔叶混交林原始林、桦木(Betula luminifera)次生林和马尾松(Pinus massoniana)人工林为对象, 采用静态箱-气相色谱法研究了3种土地利用方式(常绿落叶阔叶混交林原始林、桦木次生林和马尾松人工林)和降水减少处理状况下森林土壤CO₂、CH₄和N₂O通量排放特征, 并探讨了其环境驱动机制。研究结果表明: 原始林土壤CH₄吸收通量显著高于次生林和人工林, 次生林CH₄吸收通量显著高于人工林土壤。人工林土壤CO₂排放通量显著高于原始林和次生林土壤。次生林土壤N₂O排放通量高于原始林和人工林, 但三者间差异不显著。降水减半显著抑制了3种不同土地利用方式下林地土壤CH₄吸收通量; 降水减半处理对原始林和次生林土壤CO₂排放通量均具有显著的促进作用, 而对人工林土壤CO₂排放通量具有显著的抑制作用; 降水减半处理促进了原始林和人工林林地土壤N₂O排放而抑制了次生林林地土壤N₂O排放。原始林和次生林林地土壤CH₄吸收通量随土壤温度升高显著增加, CH₄吸收通量与土壤温度均呈显著相关关系; 原始林、次生林和人工林土壤CO₂和N₂O排放通量与土壤温度均呈显著正相关关系; 土壤湿度抑制了次生林和人工林土壤CH₄吸收通量, 其CH₄吸收通量随土壤湿度增加显著减少; 原始林土壤CO₂排放通量与土壤湿度呈显著正相关关系。自然状态下, 原始林土壤N₂O排放通量与土壤湿度呈显著正相关关系, 原始林和次生林土壤N₂O排放通量与硝态氮含量呈显著相关关系。研究结果表明全球气候变化(如降水变化)和土地利用方式的转变将对北亚热带森林林地土壤温室气体排放通量产生显著的影响。     

蚯蚓和三叉苦对亚热带人工林土壤N2O和CH4通量的短期效应

在广东鹤山大叶相思(Acacia auriculaeformis)人工林内设置外来蚯蚓西土寒宪蚓(Ocnerodrilus occidentalis)和乡土植物三叉苦(Evodia lepta)野外控制实验,用静态箱-气相色谱法对土壤N2O和CH4通量进行15 d的原位测定,研究蚯蚓和三叉苦对土壤N2O和CH4通量的影响。结果表明,三叉苦并未明显增加土壤N2O和CH4的通量,而假植物(模拟三叉苦的物理效应)则显著促进了土壤N2O的释放通量。整个实验阶段,蚯蚓效应分别使无植物对照和三叉苦处理土壤N2O通量增加了26.7%和66.3%,而在种假植物条件下,添加蚯蚓使土壤N2O通量降低了39.7%;同时,蚯蚓效应使对照处理土壤CH4吸收通量增加了10.3%,使假植物处理土壤CH4吸收通量降低了90.6%,而使三叉苦处理土壤CH4释放通量增加了301.8%。可见,蚯蚓能够促进人工林土壤N2O释放;同时促进人工林土壤从CH4“汇”向“源”转变。三叉苦的物理过程促进土壤N2O的释放,而三叉苦的生物过程抑制土壤N2O的排放。如何减缓人工林中土壤N2O和CH4的排放,必须综合考虑植物物理过程、生物过程以及蚯蚓对土壤N2O和CH4排放过程影响的独立效应和交互效应。     

下辽河平原典型农田融化期氧化亚氮和甲烷排放通量研究

应用静态箱／气相色谱法对下辽河平原典型农田（大豆地、玉米地、水稻田）土壤融化期N2O和CH4排放通量进行了研究。结果表明,在融化期间,3种农田N20排放量均较大,这段时期的农田是大气N2O的一个重要源;3种农田CH4排放不明显,成为大气CH4的汇。在融化期间,农田N2O排放量,旱田CH4排放量与箱内温度间均无显著相关性。而水稻田CH4排放量与箱内温度呈显著负相关,相对于生长季来说,这是土壤融化期间的特定现象。     

开放式空气CO2增高对稻田CH4和N2O排放的影响

在FACE(free aircarbondioxideenrichment)平台上 ,采用静态暗箱 气相色谱法观测研究了大气CO2 浓度增加对稻田CH4和N2 O排放的影响 .结果表明 ,在 15 0和 2 5 0kgN·hm-2 两种氮肥水平下大气CO2 浓度增加 2 0 0 μmol·mol-1均明显促进水稻生长 ,水稻生物量积累 .大气CO2 浓度增加对 15 0和 2 5 0kgN·hm-2 两种氮肥水平下稻田CH4排放均无显著影响 ,并简要分析了与现有文献报道结果不一致的原因 .大气CO2 浓度增加也未导致 15 0和 2 5 0kgN·hm-2 两种氮肥水平下稻田N2 O排放的明显变化 ,与大多数研究结果一致 .     

植物对沼泽湿地生态系统CO2和CH4排放的影响

利用静态暗箱/气相色谱法于2003~2005年在生长季对三江平原小叶章(Calamagrostis angustifolia)沼泽化草甸和毛果苔草(Carexlasiocarpa)沼泽地区CO2和CH4的排放通量进行野外对比观测实验。结果表明:2003~2005年生长季小叶章草甸土壤-植物系统CO2排放通量分别是土壤CO2排放通量的1.65、2.06和2.01倍,毛果苔草沼泽土壤-植物系统CO2排放通量分别是土壤CO2排放通量的2.58、2.27和4.21倍,表明沼泽湿地土壤-植物系统CO2排放通量的主要贡献者是植物地上部分的呼吸作用,且3个生长季小叶章草甸CO2排放通量均显著大于毛果苔草沼泽,主要是由于植物生物量的差异以及土壤微生物活性的不同。2003~2005年植物生长季,小叶章草甸土壤-植物系统CH4排放通量分别是土壤的4.84、3.55和6.45倍,毛果苔草沼泽土壤-植物系统CH4排放通量分别是土壤的2.60、1.25和3.22倍,且3个生长季小叶章草甸和毛果苔草沼泽CH4排放通量均具有显著差异,这主要是由于水位的差异以及植物对CH4排放能力的不同造成的。     

干扰对动物传播森林植物种子有效性影响的研究进展

干扰在森林生态系统中普遍存在,并影响森林的更新和演替.动物传播种子是种子更新的必经阶段,其对森林干扰的响应在一定程度上能够预测未来的森林群落组成和结构变化,对于明确森林演替方向具有重要意义.本文论述了森林干扰对动物传播种子有效性(包括动物传播种子的数量和质量)影响研究的生态学意义,全面揭示了自然干扰(火干扰、林窗干扰等)和人为干扰(生境破碎化、狩猎、采伐等)对动物传播种子数量、传播距离以及传播后幼苗更新影响的研究进展,指出干扰通过影响动物种群动态,进而造成动物传播种子数量发生了改变,动物传播种子的距离对干扰的响应基本表现出轻微负相关;干扰对传播后幼苗更新的影响结果因干扰类型的不同而复杂多变,干扰迹地环境因子的变化也影响着传播后的种子萌发和幼苗更新.干扰对动物传播种子有效性影响研究中存在的问题,主要表现为火干扰迹地恢复过程、增益性的干扰(如抚育、间伐、林窗)等对种子传播有效性影响研究的匮乏,以及忽略了温带森林内的干扰对动物传播种子的影响等.今后,应开展干扰对种子传播有效性的长期研究;对于干扰多发地带的森林,应高度重视增益性干扰影响动物传播植物种子的研究.     

三江平原典型沼泽湿地氧化亚氮通量

2002～2004年利用静态箱-气相色谱法对三江平原3种具有代表性的湿地类型(常年积水的毛果苔草沼泽、季节性积水的小叶章湿草甸和常年土壤过湿的灌丛湿地)进行了为期两年半的N₂O现场观测研究.结果表明,三江平原3种类型湿地N₂O通量均有明显的季节变化和年际变化,一般在非冰冻期表现为排放,冰雪覆盖期表现为微弱的吸收.生长季的N₂O通量以灌丛湿地N₂O排放通量最大,毛果苔草沼泽最小.全年平均N₂O交换通量: 毛果苔草沼泽为53.928 mg·m^-2·yr^-1,小叶章湿地为21.408 mg·m^-2·yr^-1,灌丛湿地为657.120 mg·m^-2·yr^-1,证明沼泽湿地是大气N₂O的源.3种类型湿地生长季N₂O通量无明显的日变化,与温度的相关性不大.     

Ecosystem–atmosphere exchange of CH4 and N2O and ecosystem respiration in wetlands in the Sanjiang Plain, Northeastern China

Natural wetlands are critically important to global change because of their role in modulating atmospheric concentrations of CO₂, CH₄, and N₂O. One 4‐year continuous observation was conducted to examine the exchanges of CH₄ and N₂O between three wetland ecosystems and the atmosphere as well as the ecosystem respiration in the Sanjiang Plain in Northeastern China. From 2002 to 2005, the mean annual budgets of CH₄ and N₂O, and ecosystem respiration were 39.40 ± 6.99 g C m^?2 yr^?1, 0.124 ± 0.05 g N m^?2 yr^?1, and 513.55 ± 8.58 g C m^?2 yr^?1 for permanently inundated wetland; 4.36 ± 1.79 g C m^?2 yr^?1, 0.11 ± 0.12 g N m^?2 yr^?1, and 880.50 ± 71.72 g C m^?2 yr^?1 for seasonally inundated wetland; and 0.21 ± 0.1 g C m^?2 yr^?1, 0.28 ± 0.11 g N m^?2 yr^?1, and 1212.83 ± 191.98 g C m^?2 yr^?1 for shrub swamp. The substantial interannual variation of gas fluxes was due to the significant climatic variability which underscores the importance of long‐term continuous observations. The apparent seasonal pattern of gas emissions associated with a significant relationship of gas fluxes to air temperature implied the potential effect of global warming on greenhouse gas emissions from natural wetlands. The budgets of CH₄ and N₂O fluxes and ecosystem respiration were highly variable among three wetland types, which suggest the uncertainties in previous studies in which all kinds of natural wetlands were treated as one or two functional types. New classification of global natural wetlands in more detailed level is highly expected.     

Greenhouse gas dynamics in boreal, littoral sediments under raised CO2 and nitrogen supply

SUMMARY 1. The effects of increasing CO₂ and nitrogen loading and of a change in water table and temperature on littoral CH₄, N₂O and CO₂ fluxes were studied in a glasshouse experiment with intact sediment cores including vegetation (mainly sedges), taken from a boreal eutrophic lake in Finland. Sediments with the water table held at a level of 0 or at ?15 cm were incubated in an atmosphere of 360 or 720 p.p.m. CO₂ for 18 weeks. The experiment included fertilisation with NO₃^– and NH₄⁺ (to a total 3 g N m^?2). 2. Changes in the water table and temperature strongly regulated sediment CH₄ and cCO₂ fluxes (community CO₂ release), but did not affect N₂O emissions. Increase in the water table increased CH₄ emissions but reduced cCO₂ release, while increase in temperature increased emissions of both CO₂ and CH₄. 3. The raised CO₂ increased carbon turnover in the sediments, such that cCO₂ release was increased by 16–26%. However, CH₄ fluxes were not significantly affected by raised CO₂, although CH₄ production potential (at 22 °C) of the sediments incubated at high CO₂ was increased. In the boreal region, littoral CH₄ production is more likely to be limited by temperature than by the availability of carbon. Raised CO₂ did not affect N₂O production by denitrification, indicating that this process was not carbon limited. 4. A low availability of NO₃^– did severely limit N₂O production. The NO₃^– addition caused up to a 100‐fold increase in the fluxes of N₂O. The NH₄⁺ addition did not increase N₂O fluxes, indicating low nitrification capacity in the sediments.     

生物黑炭对旱地土壤CO2、CH4、N2O排放及其环境效益的影响

采用土柱室内模拟的方法,通过添加0%、0.5%、2%、4%、6%、8%生物黑炭于土壤中,测定土壤CO2、CH4、N2O排放通量,探讨生物黑炭对旱地土壤CO2、CH4、N2O排放及其环境效益的影响。结果表明:室内模拟土柱培养期内,施用生物黑炭能显著增加CO2排放,且生物黑炭添加百分数(x)与CO2累积排放量(y)之间满足线性方程:y=12.591x+235.02(R2=0.834,n=24);当生物黑炭添加量达到2%及以上时,基本抑制了CH4的排放和显著减少土壤N2O排放,并显著减少CH4和N2O的综合温室效应,当其达到4%以上时,CH4和N2O的综合温室效应降幅更大并趋于稳定,但施用少量生物黑炭(0.5%)可显著促进N2O排放,对减少CH4和N2O综合温室效应并无明显效果。生物黑炭表观分解率随其添加量的增加逐渐减少,生物黑炭添加比例越高,积累于土壤中的碳越多,从投入生物黑炭量与固碳量和减排比角度综合考虑,农业生产中推荐生物黑炭施用量为20 t/hm2,其固碳减排效果俱佳。     

新疆天山高寒草原不同放牧管理下的CO2,CH4和N2O通量特征

以中国科学院新疆巴音布鲁克草原生态站为依托,于2010年5月—2011年10月利用静态箱-气相色谱法对短期禁牧(2005年围封)、长期禁牧(1984年围封)和自由放牧(冬季放牧)3种草地的CO2、CH4、N2O气体通量进行了野外连续试验研究。结果表明:新疆天山高寒草原对CO2,CH4和N2O通量表现出明显的季节排放特点。在植物的生长季(5—10月),新疆天山高寒短期禁牧、长期禁牧和自由放牧草原的CO2通量平均值分别为:(89.8±49.3)、(52.8±28.7)、(57.0±30.7)mg·m-2·h-1,CH4通量平均值分别为:(-66.3±21.3)、(-104.5±32.8)、(-103.0±39.0)μg·m-2·h-1,N2O通量平均值分别为:(21.2±11.8)、(13.6±6.9)、(13.2±6.2)μg·m-2·h-1;短期禁牧草原与长期禁牧和自由放牧草原CH4平均通量具有显著性差异(P0.05),但CO2和N2O差异不显著(P0.05)。在植物的非生长季(11月—翌年4月),新疆天山高寒短期禁牧、长期禁牧以及自由放牧草原的3种温室气体的通量较低且差异均不显著。     

Change in fluxes of carbon dioxide,methane and nitrous oxide due to forest drainage of mire sites of different trophy

Northern peatlands accumulate atmospheric CO₂ thus counteracting climate warming. However, CH₄ which is more efficient as a greenhouse gas than CO₂, is produced in the anaerobic decomposition processes in peat. When peatlands are taken for forestry their water table is lowered by ditching. We studied long-term effects of lowered water table on the development of vegetation and the annual emissions of CO₂, CH₄ and N₂O in an ombrotrophic bog and in a minerotrophic fen in Finland. Reclamation of the peat sites for forestry had changed the composition and coverage of the field and ground layer species, and increased highly the growth of tree stand at the drained fen. In general, drainage increased the annual CO₂ emissions but the emissions were also affected by the natural fluctuations of water table. In contrast to CO₂, drainage had decreased the emissions of CH₄, the drained fen even consumed atmospheric CH₄. CO₂ and CH₄ emissions were higher in the virgin fen than in the virgin bog. There were no N₂O emissions from neither type of virgin sites. Drainage had, however, highly increased the N₂O emissions from the fen. The results suggest that post-drainage changes in gas fluxes depend on the trophy of the original mires.     

小叶章生态系统根际土壤微生物及CO2、CH4、N2O动态

研究了培养 4 5 d的小叶章根际土壤微生物和二氧化碳 ,甲烷及氧化亚氮产生与消耗之间的关系。结果表明好氧微生物与厌氧微生物的空间分布与甲烷 ,二氧化碳及氧化亚氮的产生和氧化有着密切的关系。好氧微生物与甲烷产生呈负相关 ,与二氧化碳和氧化亚氮的产生呈正相关关系。厌氧微生物与甲烷的产生呈正相关 ,与二氧化碳和氧化亚氮的产生呈负相关关系     

Winter CO2 CH4 and N2O fluxes on some natural and drained boreal peatlands

CO₂ and CH₄ fluxes during the winter were measured at natural and drained bog and fen sites in eastern Finland using both the closed chamber method and calculations of gas diffusion along a concentration gradient through the snowpack. The snow diffusion results were compared with those obtained by chamber, but the winter flux estimates were derived from chamber data only. CH₄ emissions from a poor bog were lower than those from an oligotrophic fen, while both CO₂ and CH₄ fluxes were higher in theCarex rostrata- occupied marginal (lagg) area of the fen than in the slightly less fertile centre. Average estimated winter CO₂-C losses from virgin and drained forested peatlands were 41 and 68 g CO₂-C m^–2, respectively, accounting for 23 and 21% of the annual total CO₂ release from the peat. The mean release of CH₄-C was 1.0 g in natural bogs and 3.4 g m^–2 in fens, giving rise to winter emissions averaging to 22% of the annual emission from the bogs and 10% of that from the fens. These wintertime carbon gas losses in Finnish natural peatlands were even greater than reported average long-term annual C accumulation values (less than 25g C m^–2). The narrow range of 10–30% of the proportion of winter CO₂ and CH₄ emissions from annual emissions found in Finnish peatlands suggest that a wider generalization in the boreal zone is possible. Drained forested bogs emitted 0.3 g CH₄-C m^–2 on the average, while the effectively drained fens consumed an average of 0.01 g CH₄-C m^–2. Reason for the low CH₄. efflux or net oxidation in drained peatlands probably lies in low substrate supply and thus low CH₄ production in the anoxic deep peat layers. N₂O release from a fertilized grassland site in November–May was 0.7 g N₂O m^–2, accounting for 38% of the total annual emission, while a forested bog released none and two efficiently drained forested fens 0.09 (28% of annual release) and 0.04 g N₂O m^–2 (27%) during the winter, respectively.