土地利用史对水田甲烷的排放和甲烷植物的影响

The characteristics of methane emission were compared among six types of upland and paddy soils developed from different materials with distinct physical and chemical properties after planting rice.The fluxes of methane emission in submerged soils from the upland were obviously lower than those from the paddy rice field.The flux of methane emission in the paddy soil developed from fluvo-aquic soil was the largest among all the types of soils.Planting of rice was heplful to emission of methane in soils.The amounts of various groups of methanogenic flora were conformed with the differences among the fluxes of methane emission in various types of soils.Methane formation was observed in each type of air-dried soils stored for a long time after addition of water and incubation at 35℃.     

上海地区水稻土氮素矿化模拟

Three types of paddy soils, derived from granite, Quaternary red clay and basalt, respectively, were selected to study the effects of Fe and Mn in paddy soils on methane production and emission through pot and incubation experiments. The results indicated that the difference of Fe and Mn in paddy soils was one of the important factors causing obvious differences in methane emission from different soil types. Soil Fe and Mn affecting methane emission from the paddy soils was likely through affecting soil Eh and forming Fe and Mn plaques on rice roots. Different rates and valences of added Fe and Mn significantly affected methane production from paddy soils. Therefore, this study enhanced understanding of processes controlling methane emission from paddy soils and may help to improve modeling and estimating regional and global methane emission from paddy soils.     

中国东北休闲期稻田温室气体排放

CH4, N2O and CO2 emissions from northeast Chinese rice fields were measured in the fallow season （November to March） to investigate the effects of freezing-thawing on the emissions. Both CH4 emission from and atmospheric CH4 oxidation by the soil occurred, but the flux was small. During the fallow season, rice fields acted as a minor source of atmospheric CH4, which accounted for about 1% of the CH4 emission during the rice growing period. The field was also a substantial source of atmospheric N20, which ranged between 40 to 77 mg m-2 and eu=counted for 40%-50% of the annual N20 emission. The largest N20 flux was observed in the thawing period during the fallow season. Laboratory incubation tests showed that the largest N20 flux came from the release of N20 trapped in frozen soil. Tillage and rice straw application （either mulched on the soil surface or incorporated in the soil） stimulated the CH4 and CO2 emissions during the fallow season, but only straw application stimulated N2O emission substantially.     

封闭系统水稻土甲烷氧化的模拟

Methane oxidation by paddy soils in a closed system could be simulated by the equation x=k1xo/(k1 k2x0)exp(k2t)-k2x0 where x0 and x are the CH4 concentrations at time zero and t,respectively;k1 and k2 are constants related to the constant of first-order-kinetics.According to the equation the change of soil ability to oxidize CH4 could be estimated by the equation Ac=k2/k1(x0-x)x0k2/k1-1.The results showed that the soil ability to oxidize CH4 varied,depending on the initial CH4 concentration.High initial CH4 concentration stimulated soil ability to consume CH4,while low concentration depressed the ablility.This characteristic of paddy soil seemed to be of considerable significance to self-adjusting CH4 emission from flooded rice fields if there exist oxic microsites in the soil.     

稻田土壤甲烷排放模型: Ⅰ. 模型的建立

With an understanding of the processes of methane production, oxidation and emission, a semi-empirical model, focused on the contributions of rice plants to the processes and also the influence of environmental factors, was developed to predict methane emission from rice paddy soils. In the present model, the amount of methane transported from the soil to the atmosphere was determined by the rates of CH₄ production and an emitted fraction. The rates of CH₄ production in irrigated rice soils were computed from the availability of methanogenic substrates that are primarily derived from rice plants and added organic matter and the influence of soil texture, soil redox potential and temperature. The fraction of methane emitted was assumed to be modulated by the rice plants and declines with rice growth and development. To make it applicable to a wider area with limited data sets, a simplified version of the model was also derived to predict methane emission in a more practical manner.     

南亚热带森林干季期间土壤变湿后一氧化氮排放

Information about soil nitric oxide (NO) emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, we measured NO fluxes following wetting of dry soil in a broadleaf forest and a pine forest in subtropical China. Large pulses of NO fluxes were observed after soil wetting in both forests. NO fluxes increased significantly within 0.5 h following wetting in both forests and reached peak 1 h and 4 h after soil wetting in the pine forest and the broadleaf forest, respectively. In the broadleaf forest, averaged peak flux of NO pulses was 157 ng N m–2 s–1, which was 8 times the flux value before wetting, and in the pine forest, the averaged peak flux was 135 ng N m–2 s–1, which was 15.5 times the flux value before wetting. The total pulses-induced NO emissions during the dry season were roughly estimated to be 29.4 mg N m–2 in the broadleaf forest and 22.2 mg N m–2 in the pine forest or made up a proportion of 4.6% of the annual NO emission in the broadleaf forest and 5.3% in the pine forest.     

中国湖南省主要水稻土类型的氨固定

The contents, affecting factors, seasonal changes and availability of fixed ammonium in major types ofpaddy soils derived from different parent materials in Hunan Province, China, were studied using the Silva-Bremner method by laboratory and pot experiments. Results showed that the content of fixed ammoniumin the plough horizons ranged from 88.3 mg kg-1 to 388.1 mg kg-1, with 273.2 ± 77.7 mg kg-1 on average,accounting for 11.2% of total soil N on average. Content of fixed ammonium decreased in the order of newlylacustrine clayey paddy soil ＞ alluvial sandy paddy soil ＞ purple clayey paddy soil ＞ newly alluvial sandypaddy soil ＞ yellow clayey paddy soil ＞ reddish-yellow clayey paddy soil ＞ granitic sandy paddy soil. Therewere four distribution patterns of fixed ammonium in the profiles to 1-m depth, i.e., increase with the depth,decrease with increasing depth, no distinct change with the depth, and abrupt increase or decrease in somehorizon. Percentage of fixed ammonium in total N increased with the depth in most of the soils. Fixationof NH4+ by soil was higher at 30 ℃ than at 20 ℃ and 40 ℃, and continuous submergence benefited thefixation of NH4+ in newly alluvial sandy paddy soil, purple clayey paddy soil and alluvial sandy paddy soil,while alternating wetting and drying contributed to the fixation of NH4+ in yellow clayey paddy soil mostly.Fixed ammonium content in the test paddy soils was significantly correlated with ＜ 0.01 mm clay content(P ＜ 0.05), but not with ＜ 0.001 mm clay content, total N, organic N and organic matter. Fixed ammoniumcontent varied with rice growth stages. Application of N fertilizer promoted fixation of NH4+ by soil, and Nuptake by rice plant promoted release of fixed ammonium from the soil. Recently fixed ammonium in paddysoil after N fertilizer application was nearly 100% available to rice plant, while native fixed ammonium wasonly partly available, varying with the soil type and rice type.     

Characteristics of Humic Substances in Paddy Soils

In the present paper,the composition of humus and the charateristics of humic acid from seven paddy soils were compared with those of upland (and/or natural) soils.Results show that:(1) in each group of the soil samples for comparison the HA/FA ratio of the humus of a paddy soil,in most cases,was appreciable higher than that of adjacent upland(and/or natural) soil derived from the same parent material;(2) the humic acid extracted from the paddy soils was characterized by a higher C/O ratio,a higher content of methoxyl groups,and a lower content of carboxyl groups than those from the corresponding upland (and/or natural) flooded soils,implying that the humic acid formed under rice cultivation is in a lower degree of humification than that formed under upland(and/or natural) conditions;and (3) the humic acid of paddy soils,however,was not always characterized by a lower aromaticity than that of the corresponding upland(and/or natural) soils.     

基于多年田间实验的尿素和控释尿素肥料对稻田甲烷排放的影响研究

A four-year(2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier(CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4ha-1in treatments CK(zero N), U(urea) and C(CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7%(P 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration(MSA) starting on D30(30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.     

Fractionation of Zinc in Paddy Soils of China

The rice fields in China amount to 25.4 million hectares of which low yield paddy soils areabout 26％(Xu,1981;Xiao,1981).One of the most important causes of low yield is the defi-ciency in nutrients including zinc.Zinc deficiency usually occurs in calcareous paddy soils withpH>6.5(Zhu and Liu,1981).And the availability of zinc in calcareous paddy soils is lowerthan that in neutral and acid paddy soils.     

华南地区覆膜旱种稻田甲烷排放及其与土壤水分和温度的关系

采用静态箱法和田间小区试验,研究了常规稻田和覆膜旱种稻田水稻全生育期CH4的排放规律,探讨了温度和水分与稻田CH4排放的关系。结果表明:覆膜旱种稻田的甲烷排放量明显低于常规水田的排放量,常规水田的甲烷累计排放通量为20.38g/m2,覆膜旱种稻田为2.46g/m2,水稻覆膜旱种后甲烷排放量降低了88%。常规水田CH4排放峰期持续了35d,覆膜旱种稻田CH4排放峰期为25d,两者在CH4排放高峰期的排放量分别占整个生育期累计排放量的72%和97%。覆膜旱作稻田CH4排放量降低,主要表现在最大排放峰值降低和排放峰持续时间缩短。土壤温度(5cm处)和水分与水稻生育期稻田甲烷的排放有显著正相关。CH4排放通量大于1.0mg·m-2·h-1主要集中在土壤质量含水率高于36.25%的区域,在土壤质量含水率小于36.25%时,常规稻田和覆膜旱种稻田都只有少量CH4排放。     

水肥管理对稻田CH4排放及其全球增温潜势影响的评估

甲烷(CH_4)是主要温室气体之一,对全球增温的作用仅次于二氧化碳(CO_2)。稻田是CH_4的重要排放源,减少稻田CH_4排放对减缓气候变暖具有直接效应。为此,掌握稻田CH_4排放的规律和特征对控制和减少稻田CH_4排放尤为重要。为了解稻田温室气体排放的主要影响因子及影响程度,估算稻田温室气体全球增温潜势,寻求农田减排措施,我们通过收集已发表的文献建立了稻田CH_4排放的数据库,采用析因分析与回归分析方法对稻田CH_4日排放量和全球增温潜势特征和可能的影响因子进行了分析。结果表明,稻田CH_4日排放量和增温潜势均随土壤有机质背景含量的升高而增加,不同类型稻田CH_4日排放量大小依次为:双季稻晚稻双季稻早稻单季稻稻麦轮作晚稻;晚稻田CH_4的增温潜势大于早稻田。不同肥料处理条件下,稻田CH_4日排放量表现为:秸秆还田配施有机肥化学氮肥≈生物炭。控制灌溉水量可降低稻田CH_4的综合增温潜势,表现为:持续淹水晒田干湿交替控制灌溉。研究结果说明,稻田CH_4的产生与排放过程受土壤有机质含量、肥料管理和水分管理以及轮作制度等多种因素的共同影响,应依据不同土壤条件和种植制度,适当调整肥水管理,以减少稻田温室气体排放,降低其增温潜势。     

耕种制度对西南地区冬水田甲烷排放的影响

1995年5月15日～1997年5月15日两年在田间条件下研究我国西南地区冬水田甲烷排放量及耕种制度的影响。结果表明冬水田水稻生长期甲烷排放通量在0．47～171．12mg／m2     

三江平原寒地稻田CH_4、N_2O排放特征及排放量估算

利用静态暗箱-气相色谱法,于2003-2006年对三江平原寒地稻田CH4、N2O通量进行了为期4年的田间原位观测研究.结果表明:三江平原寒地稻田CH4和N2O排放具有明显的季节变化,水稻生长季淹水期是CH4排放的强源,稻田排水后CH4排放显著下降,休闲期CH4排放微弱或呈弱吸收汇,整个生长季CH4排放呈现单峰型态,并随水稻植株生长和叶面积指数而变化;水稻生长季和休闲期N2O排放通量都很小,冬季休闲期有时还出现微弱的吸收现象.生长季一般在施肥和表土落干时都会出现不同强度的排放峰,除了几次比较显著的排放峰值外,其它淹水状态下N2O排放很弱;温度和土壤水分状况是影响稻田CH4和N2O排放的重要因子,稻田积水深度和气体排放无明显的相关性;水稻植株对稻田土壤CH4排放起促进作用而对稻田土壤N2O排放起抑制作用;稻田氮肥用量增加可以降低土壤CH4排放,但却增加了N2O的排放.根据试验数据对三江平原地区寒地稻田CH4和N2O排放总量估算值分别为0.1035 Tg/a和0.0021 Tg/a.     

水稻土甲烷产生、氧化和排放过程的相互影响①——以水分历史处理为例

通过盆栽和培养试验研究了不同水分历史水稻土CH4产生、氧化及排放间的相互影响。水稻土CH4产生、氧化和排放皆受土壤水分历史条件的强烈影响,非水稻生长期土壤水分含量越高,随后水稻生长期CH4排放量越大,产生和氧化能力也越强。无论是水稻生长期平均值还是季节变化,CH4排放皆受CH4产生的显著影响。CH4产生量和排放量的相对差值很好地说明了各处理间土壤CH4氧化潜力的差异。水稻土CH4排放通量主要受CH4产生率,而不是CH4氧化潜力的影响,但CH4氧化能牵制CH4产生率对CH4排放通量的影响,水稻土这种自然调节CH4排放量的特性对减少稻田CH4排放具有重要的意义。     

不同灌溉模式和施氮处理下稻田 CH4 和 N2O 排放

【目的】研究不同灌溉模式和施氮处理稻田 CH₄ 和 N₂O 的排放规律、综合增温潜势和综合排放强度,以期获得降低稻田 CH₄ 和 N₂O 排放的灌溉模式和施氮管理。【方法】2015～2016 年在广西南宁市灌溉试验站进行晚稻和早稻大田试验,两次试验均设 3 种灌溉模式:常规灌溉 (CIR)、“薄浅湿晒 ”灌溉 (TIR) 和干湿交替灌溉 (DIR)。 2 种尿素-N 和猪粪-N 比例:100% 尿素-N (FM1),50% 尿素-N + 50% 猪粪-N (FM2)。共设 CIR-FM1、TIR-FM1、DIR-FM1、CIR-FM2、TIR-FM2 和 DIR-FM2 6 个处理,用静态箱–气相色谱法测定了水稻生育期内稻田 CH₄ 和 N₂O 排放通量,分析了早晚稻生育期内 CH₄ 和 N₂O 累积排放量和综合增温潜势,并结合产量分析了 CH₄ 和 N₂O 综合排放强度。【结果】DIR 下 FM2 处理早稻产量和两季总产量比 FM1 处理分别提高 18.8% 和 17.7%,FM2 下 TIR 和 DIR 模式早稻产量分别比 CIR 模式提高 20.9% 和 37.4% 以及 DIR 模式两季总产量比 CIR 模式提高 21.5%。不同处理早晚稻生育前期 CH₄ 排放通量较高,生育中后期 CH₄ 排放通量较低。水稻生育期内 TIR 和 DIR 模式 CH₄ 累积排放量低于 CIR 模式,FM1 处理 CH₄ 累积排放量低于 FM2 处理。不同处理早晚稻生育前期 N₂O 的排放通量为负值或者较低,N₂O 排放主要集中在晒田完成复水之后及成熟期稻田水分落干时,DIR 模式 N₂O 累积排放量显著高于 CIR 模式,FM2 处理 N₂O 累积排放量高于 FM1 处理。不同处理稻田 CH₄ 和 N₂O 的排放彼此间存在消长关系。CH₄ 对综合增温潜势的贡献率达 99% 以上,而 N₂O 的贡献率不足 1%。3 种灌溉模式下 FM1 处理 CH₄ 或 N₂O 增温潜势、CH₄ 和 N₂O 综合增温潜势和排放强度均低于 FM2 处理,2 种施氮处理下 TIR 和 DIR 模式 CH₄ 和 N₂O 综合增温潜势和排放强度低于 CIR 模式。【结论】与常规灌溉相比,“薄浅湿晒”灌溉水稻产量和 N₂O 排放有所提高,但是降低 CH₄ 排放量及 CH₄ 和 N₂O 综合增温潜势和排放强度;干湿交替灌溉增加水稻产量和 N₂O 排放,但是降低 CH₄ 的排放量及 CH₄ 和 N₂O 综合增温潜势和排放强度,因此,“薄浅湿晒”和干湿交替灌溉模式是有效降低稻田 CH₄ 和 N₂O 综合增温潜势和排放强度的两种灌溉模式。在这两种灌溉方式下,与猪粪尿素配施相比,单施尿素显著降低 CH₄ 和 N₂O 综合增温潜势和排放强度。     

水分状况对水田土壤N2O排放的影响

通过室内培养试验,研究了不同水分含量下水稻土的Ｎ２Ｏ排放,结果表明,在水分含量相当于田间持水量时,土壤具有最大的Ｎ２Ｏ排放速率,当水分含量在田间持水量之上时,反硝化作用是Ｎ２Ｏ的主要来源。水分含量在田间持水量之下时,尽管硝倾作用强烈,但Ｎ２Ｏ排放量较小。通过温室盆栽试验研究了不同水分管理措施下,水稻土Ｎ２Ｏ和ＣＨ４的排放,同常规水分管理方式相比,长期淹水显著增加ＣＨ４的排放而减少了Ｎ２Ｏ的排放。相反,湿润灌溉的处理在整个水稻生长期内没有明显的ＣＨ４排放,但其Ｎ２Ｏ排放对水分状况敏感,出现数次峰值,从而总排放量远高于其它两处理。     

生物质炭输入减少稻田痕量温室气体排放

为揭示不同水平生物质炭输入对稻田土壤理化性质、水稻产量及温室气体排放的影响,采用自制竹炭在4种不同施用水平下(0、10、20、40 t/hm2)输入稻田土壤,开展了水稻一个生长周期的田间试验。结果表明,生物质炭输入可显著提高土壤p H值和有机碳含量(P0.05),且有机碳含量增幅与生物质炭施用水平呈正比(相关系数为0.78,P0.01)。生物质炭施用可显著降低土壤容重(P0.05),最大降幅为0.25 g/cm3,土壤容重随着生物质炭施用量的增加而降低。不同处理水稻产量无显著性差异(P0.05)。CH4累积排放量与生物质炭施用量呈负相关性(相关系数为-0.24,P0.01),投加生物质炭可显著降低稻田CH4排放通量和累积排放量(P0.05),但过量施用生物质炭(超过20 t/hm2)并不能显著降低CH4累积排放量(P0.05)。相比对照处理(不输入生物质炭),生物质炭输入后一周内可显著性降低N2O排放通量(P0.05),并在排水烤田时升高,最终稳定于9.80 mg/(m2·h)。生物质炭输入可显著性降低N2O累积排放量(P0.05),但不同水平生物质炭输入处理之间差异不显著(P0.05)。该试验条件下,生物质炭施用量为20 t/hm2时可实现稻田稳产和固碳减排目标,该研究可为太湖地区苕溪流域稻田增汇和温室气体减排提供参考。     

水稻根系生物特性与稻田温室气体排放相关性研究

通过湖南双季稻区温室气体排放差异的水稻品种田间试验,研究了不同品种温室气体排放与根系特征的相关性。结果表明,早稻分蘖盛期CH4排放通量与根干重、伤流量均呈显著负相关（P〈0.05）;晚稻CH4排放通量与根伤流量呈极显著负相关（P〈0.01）;早稻N2O排放通量在分蘖盛期与根伤流量相关性极显著（P〈0.01）,在齐穗期与根体积、干重、根伤流量均呈极显著负相关（P〈0.01）;晚稻分蘖盛期,根系干重与体积均与N2O排放通量呈显著正相关（P〈0.05）;齐穗期,根系体积与N2O排放通量呈显著负相关（P〈0.05）;早稻分蘖盛期CO2排放通量与根系干重和根伤流量呈显著正相关关系（P〈0.05）,晚稻齐穗期根系伤流量与CO2排放通量负相关性达到极显著水平（P〈0.01）。因此,根系特性是影响水稻温室气体排放的重要因素。