博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O排放通量

为研究干旱区淡水湖泊人工、天然芦苇湿地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,于2015年1月—12月对博斯腾湖人工和天然芦苇湿地土壤CO_2、CH_4和N_2O通量进行全年观测。结果表明,人工芦苇湿地土壤CO_2、CH_4和N_2O排放通量变化范围分别为:10.1—588.4mg m~(-2)h~(-1)、2.9—82.4μg m~(-2)h~(-1)和1.32—29.7μg m~(-2)h~(-1),天然芦苇湿地土壤CO_2、CH_4和N_2O排放通量变化范围分别为10.3—469.6mg m~(-2)h~(-1)、3.1—64.8μg m~(-2)h~(-1)和1.9—14.3μg m~(-2)h~(-1)。人工和天然芦苇湿地夏季土壤CO_2排放通量均明显高于其他季节,而土壤CH_4和N_2O排放通量较大值多集中在春末夏初。全年观测期间,人工芦苇湿地土壤CO_2、CH_4和N_2O排放通量高于天然芦苇湿地(P0.05);温度是影响人工、天然芦苇湿地土壤CO_2和N_2O排放通量的关键因素,近地面温度和5cm土壤温度与CO_2和N_2O排放通量呈现极显著的正相关关系(P0.01)。土壤CH_4排放通量是温度和水分二者共同影响的,由近地表温度、5cm土壤温度和土壤含水量共同拟合的方程可以分别解释人工、天然芦苇湿地土壤CH_4排放通量的71%、74.5%;土壤有机碳、pH、盐分、NH_4~+-N、NO_3~--N也是人工、天然芦苇湿地土壤CO_2、CH_4和N_2O排放通量的影响因素;人工和天然芦苇湿地土壤均是CO_2、CH_4和N_2O的"源"。基于100年尺度,由3种温室气体计算全球增温潜势得出,人工芦苇湿地全球增温潜势大于天然芦苇湿地(15150.18kg/hm~212484.21kg/hm~2)。     

模拟SO42-沉降对闽江口淡水感潮野慈姑湿地甲烷排放通量的影响

2015年12月—2016年10月,每月小潮日原位定期向闽江口塔礁洲淡水感潮野慈姑(Sagittaria trifolia L.)湿地施加剂量为60、120 kg S hm~(-2)a~(-1)的K_2SO_4溶液(分别记做S-60和S-120),探讨模拟硫酸根(SO_4~(2-))沉降对河口淡水感潮湿地甲烷(CH4)排放通量及间隙水SO_4~(2-)浓度的影响。对照、S-60和S-120处理组CH_4排放通量年均值分别为(7.88±1.00)mg h~(-1)m~(-2)、(6.55±0.97)mg h~(-1)m~(-2)和(6.66±1.49)mg h~(-1)m~(-2)。在年尺度上,两个高强度模拟SO_4~(2-)沉降处理组均未显著降低闽江口淡水感潮野慈姑湿地CH_4排放通量(P0.05),即高强度SO_4~(2-)沉降不会对河口淡水感潮湿地CH_4排放通量产生类似于其对泥炭湿地和水稻田的显著抑制效应。在年尺度以及秋、冬季,两个施加K_2SO_4溶液处理显著增加了野慈姑湿地10 cm深度土壤间隙水SO_4~(2-)浓度。对于各个处理组,温度较高的夏、秋季CH_4排放通量均显著高于温度相对较低的冬、春季(P0.05)。不同处理组CH_4排放通量均与土壤温度呈显著正相关关系,温度仍然是影响亚热带河口淡水感潮湿地CH_4排放通量的重要环境因子。     

神农架主要森林土壤CH4、CO2和N2O排放对降水减少的响应

研究降水格局改变后森林土壤温室气体排放格局,可为森林温室气体排放清单制定提供科学依据。以神农架典型森林类型常绿落叶阔叶混交林和2种人工林马尾松和杉木林为研究对象,研究了降水格局改变后,其土壤CH_4吸收、CO_2和N_2O的排放格局和可能机制。结果表明:常绿落叶阔叶混交林吸收CH_4通量为(-36.79±13.99)μg Cm~(-2)h~(-1),显著大于马尾松和杉木两种人工林的CH_4吸收通量,其吸收通量分别为(-14.10±3.38)μg Cm~(-2)h~(-1)和(-7.75±2.80)μg Cm~(-2)h~(-1)。马尾松和杉木两种人工林CO_2排放通量分别为(107.03±12.11)μg Cm~(-2)h~(-1)和(80.82±10.29)μg Cm~(-2)h~(-1),显著大于常绿落叶阔叶混交林(71.27±10.59)μg Cm~(-2)h~(-1)。常绿落叶阔叶混交林N_2O排放通量为(8.88±6.75)μg Nm~(-2)h~(-1),显著大于杉木人工林(5.93±2.79)μg Nm~(-2)h~(-1)和马尾松人工林(1.64±1.02)μg Nm~(-2)h~(-1)。分析3种森林土壤CH_4吸收量与其环境因子之间的关系发现,常绿落叶阔叶混交林的CH_4吸收通量与其土壤温度呈现显著的指数负相关关系(P0.01)。常绿落叶阔叶混交林、马尾松林和杉木林的土壤CO_2排放通量与其空气温度和土壤温度之间均呈现显著的指数正相关关系(P0.01)。常绿落叶阔叶混交林和马尾松林土壤N_2O排放通量与空气温度之间均呈现显著的指数正相关关系(P0.01),而马尾松林与土壤温度之间呈显著正相关(P0.05),与土壤湿度之间均无显著相关。降水减半后,减少降水对常绿落叶阔叶混交林和马尾松林土壤CH_4吸收通量均具有明显的促进作用,但对杉木林土壤CH_4吸收量具有抑制作用,对常绿落叶阔叶混交林和杉木林土壤CO_2平均排放通量均具有明显的促进作用,而对马尾松林土壤CO_2平均排放通量明显抑制作用,对常绿落叶阔叶混交林、马尾松和杉木林土壤N_2O排放量具有明显的抑制作用。     

大兴安岭永久冻土区7种沼泽类型土壤温室气体排放特征

气候变暖及永久冻土退化将会增加冻土湿地的温室气体排放,但关于大兴安岭永久冻土区沼泽湿地温室气体通量及主控因子尚不明确。采用静态箱-气相色谱法,同步原位观测大兴安岭永久冻土区7种天然沼泽类型(草丛沼泽-C、灌丛沼泽-G、毛赤杨沼泽-M、白桦沼泽-B、落叶松苔草沼泽-LT、落叶松藓类沼泽-LX、落叶松泥炭藓沼泽-LN)土壤CO_2、CH_4和N_2O通量及土壤温度、水位、化冻深度及土壤碳氮含量、碳氮比、pH值及含水量,揭示永久冻土区沼泽土壤温室气体通量及其主控因子。结果表明:1) 7种沼泽类型土壤CO_2年均通量(125.12—163.33 mg m~(-2) h~(-1))相近;2) CH_4年均通量(-0.007—0.400 mg m~(-2) h~(-1))呈草丛显著高于其他沼泽5.6—65.7倍(P0.01);3) N_2O年均通量(1.52—37.90μg m~(-2) h~(-1))呈阔叶林沼泽显著高于其他类型2.0—23.9倍,针叶林沼泽显著高于草丛、灌丛沼泽2.9—6.2倍(P0.05);4) CO_2主控因子为土壤温度和水位;CH_4主控因子为土壤温度和化冻深度;N_2O受到多种环境因子综合调控,共同可以解释N_2O变化的26%—99%;5)土壤增温潜势(11.05—15.37 t CO_2 hm~(-2) a~(-1))相近,且均以CO_2占绝对优势地位,但草丛以CH_4占次要地位,森林沼泽则以N_2O占次要地位。综合对比国内外现有研究结果发现目前大兴安岭永久冻土区沼泽土壤仍处于CO_2、CH_4和N_2O低排放阶段。     

张掖湿地甲烷通量动态特征及其影响因子

于2012年7月—2014年6月对地处干旱区的张掖湿地甲烷(CH_4)通量进行观测,分析其CH_4通量的变化特征及其影响因子。结果表明:CH_4通量的日变化趋势总体表现为白天大于夜间;不同季节CH_4通量排放特征差异明显,夏季最大,春秋次之,冬季最小;CH_4通量日总量与空气温度、土壤温度之间指数相关关系显著,其中4 cm处土壤温度与之相关性最强;1—6月摩擦风速(U*)与CH_4通量显著正相关;结合CO_2通量观测数据,研究时段张掖湿地净碳吸收量为495.92 g C m~(-2)a~(-1),为明显碳汇。     

植被恢复对库布齐沙漠非生长季土壤CH4、N2O通量的影响

荒漠土壤温室气体排放是陆地碳氮循环的重要组成部分,目前人工建植促进植被恢复对非生长季荒漠土壤CH_4、N_2O通量的影响尚不明确。本研究采用静态暗箱-气相色谱和时空替代法,分析非生长季库布齐沙漠东部不同植被恢复阶段土壤CH_4、N_2O通量特征及其与环境因子之间的关系,探讨植被恢复对非生长季荒漠土壤温室气体排放的影响。结果表明:非生长季荒漠土壤是CH_4的吸收汇,也是N_2O的排放源。不同植被恢复阶段CH_4平均吸收量和N_2O排放量均表现为:苔藓结皮固定沙地(47.6μg CH_4 m~(-2) h~(-1), 13.5μg N_2O m~(-2) h~(-1))地衣结皮固定沙地(32.2μg CH_4 m~(-2) h~(-1), 9.1μg N_2O m~(-2) h~(-1))藻结皮固定沙地(23.7μg CH_4 m~(-2) h~(-1), 8.7μg N_2O m~(-2) h~(-1))半固定沙地(22.4μg CH_4 m~(-2) h~(-1), 5.0μg N_2O m~(-2) h~(-1))流动沙地(18.7μg CH_4 m~(-2) h~(-1), 3.9μg N_2O m~(-2) h~(-1))。荒漠土壤在不同冻结时期温室气体排放存在较大差异,融冻期CH_4吸收贡献率最大,在结冻期N_2O排放贡献率最大。非生长季荒漠土壤存在明显的水热同期现象,土壤水热因子对N_2O通量的影响较小,仅半固定沙地土壤温度与N_2O通量呈显著正相关;而在藻类、地衣和苔藓结皮固定沙地中,土壤温度和含水量均与CH_4通量呈显著负相关。植被恢复过程中,生物量的积累和土壤理化性质的改善,能够显著影响荒漠土壤CH_4、N_2O通量的变化。因此,人工建植促进植被恢复实现沙漠化逆转可改变荒漠生态系统的温室气体排放格局。     

翅碱蓬对盐沼沉积物微生物生物量及β-氨氧化细菌群落的影响——以双台河口为例

为了解翅碱蓬植被对盐沼沉积物微生物的影响,于2013年7月、8月、9月和11月对双台河口裸滩和翅碱蓬植被沉积物(10—15 cm)微生物生物量碳(MBC)、微生物生物量氮(MBN)、16S rRNA基因丰度、潜在硝化速率、β-氨氧化细菌(β-AOB)丰度及群落进行了调查。结果表明,不同采样日期裸滩沉积物MBC、翅碱蓬沉积物β-AOB amo A丰度和两种生境潜在硝化速率没有显著差异;而翅碱蓬沉积物MBC、裸滩沉积物β-AOB amo A丰度、两种生境MBN和16S rRNA基因丰度呈现时间波动。当所有采样日期的数据结合分析时,翅碱蓬植被显著影响沉积物MBC、MBN、细菌16S rRNA基因丰度、潜在硝化速率和β-AOB amo A丰度。从裸滩和翅碱蓬沉积物获得的β-AOB序列属于Nitrosospira和Nitrosomonas,翅碱蓬植被对β-AOB群落结构和多样性均有一定的影响。研究结果有助于了解翅碱蓬湿地中微生物的作用,为盐沼生境的生态修复技术提供参考。     

内蒙古草原温室气体交换通量

草地生态系统是地球上十分重要的陆生生态系统,内蒙古草原在我国草地生态系统中占有重要地位,其在全球温室气体收支平衡中扮演重要角色。统计分析内蒙古地区34个观测地点的多年(1995—2012)温室气体观测数据,得到内蒙古3种主要草原类型(草甸草原、典型草原、荒漠草原)主要温室气体(CO2、CH4、N_2O)的年度或生长季平均通量并据此判断其温室气体源汇类型,并选择内蒙古草原中分布最广泛的典型草原的温室气体交换通量与环境因子进行相关性分析。结果显示,典型草原、荒漠草原表现为CO2交换源汇动态变化的过程(生长季交换通量分别为(-4.26±15.57)mg C m~(-2)h~(-1)、(-42.5±5.42)mg C m~(-2)h~(-1)表现为汇,年度交换通量分别为(20.64±11.54)mg C m~(-2)h~(-1)、(18.04±2.48)mg C m~(-2)h~(-1)表现为源),草甸草原CO2年度交换通量为(-10.31±1.15)mg C m~(-2)h~(-1)表现为汇;草甸草原、典型草原、荒漠草原CH4年度交换通量分别为(-30.48±9.57)μg C m~(-2)h~(-1)、(-41.25±3.61)μg C m~(-2)h~(-1)、(-85.00±51.03)μg C m~(-2)h~(-1),均表现为CH4的汇、N_2O年度交换通量分别为(28.40±7.27)μg N m~(-2)h~(-1)、(3.18±0.91)μg N m~(-2)h~(-1)、(2.51±0.67)μg N m~(-2)h~(-1),均表现为N_2O的源。在典型草原温室气体交换通量与环境因子的相关性分析中发现,CH4平均吸收通量与降水量(P0.05)、土壤湿度(P0.05)、土壤温度(P0.01)有显著或是极显著线性正相关关系;CO2平均通量与降水量(P0.01)、土壤湿度(P0.01)、叶面积指数(P0.01)有极显著线性负相关关系,与气温(P0.01)有极显著线性正相关关系;N_2O平均通量与降水量(P0.05)、土壤湿度(P0.05)、气温(P0.01)有显著或极显著的线性正相关关系。     

放牧对若尔盖高原湿地CH4排放的影响

湿地是大气甲烷(CH_4)的主要排放源,而有关放牧对湿地CH_4排放的影响特征仍未得到足够的报道。因此,通过静态箱法,研究了放牧对四川省若尔盖高原湿地CH_4排放的影响,CH_4气体通过快速温室气体分析仪测量。结果表明:放牧样地和围栏内样地生长季CH_4排放量为(31.32±19.57)g/m~2和(30.31±23.46)g/m~2,它们之间无差异显著;但是集中放牧期间(7—9月),放牧样地(21.01±12.35)g/m~2较围栏内样地显著增加了CH_4排放量为54.3%。2014年生长季期间通过刈割植物模拟放牧表明两种刈割强度CH_4排放量为(5.01±5.37)g/m~2和(4.69±5.99)g/m~2,较未刈割样地(1.15±1.89)g/m~2增加了335.9%和308.0%,其原因可能是放牧或者刈割减少地表植物生物量,降低植物高度,缩短了CH_4排放的路径距离。该结果可为我国高原湿地保护与管理决策提供基础数据支撑。     

黄河三角洲潮间带不同类型湿地景观格局变化与趋势预测

以1979—2013年7期卫星遥感影像(Landsat TM)为数据源,结合野外实地调查,通过建立黄河三角洲潮间带湿地数据库,探讨不同类型湿地的景观格局以及自然与人为因素对景观格局变化的影响,并基于Markov模型对未来20年三角洲潮间带不同类型湿地的景观格局进行了趋势预测。结果表明,三角洲的潮间带湿地面积在1979—2013年间整体呈先降低后增加变化。其中,1979—2010年的湿地面积持续减少,由1050.28 km~2减少为575.39 km~2,减少率为45.22%;2010—2013年的湿地面积略有增加,由575.39 km~2增加为596.17 km~2,增长率为0.36%。1979—2013年,潮间带主要湿地景观类型随距海远近均呈明显带状分布,但芦苇湿地面积呈明显降低趋势(减少273.53 km~2,减少率为79.68%),盐田养殖池面积呈显著增加趋势(增长12.04km~2,增长率为1584.21%),而光滩、碱蓬湿地、碱蓬-柽柳湿地和柽柳-芦苇湿地等其它类型湿地面积整体均呈波动减少趋势。未来20年,潮间带湿地面积整体将呈降低趋势,其值将由2010年的575.39 km~2减少为2030年的546.98 km~2,减少率为6.60%。芦苇湿地面积将继续减少(减少30.16 km~2,减少率为24.12%),盐田养殖池面积将持续增长(增加3.71 km~2,增长率为38.61%),而光滩、碱蓬湿地、碱蓬-柽柳湿地和柽柳-芦苇湿地等其它类型湿地面积均将呈小幅波动变化。研究发现,尽管自然与人为驱动力的双重作用决定了1979—2013年间潮间带的湿地景观格局及其动态变化,但黄河年输沙量(x_1)、区域GDP(x_2)和水产品产量(x_3)对潮间带湿地面积变化(y)的影响更为重要(y=733.192+35.317 x_1-0.005 x_2-4.085 x_3,P=0.00010.05),其对过去30多年间潮间带湿地面积变化的解释贡献高达76.7%。随着黄河三角洲高效生态经济区国家战略的实施,为实现潮间带区域的可持续发展,潮间带湿地的保护与生态保育应给予特别重视。     

Methane Release through Resuspension of Littoral Sediment

Sediment in the littoral zone of lakes is frequently disturbed by wave action or bioturbation, resulting in sediment resuspension. In undisturbed sediment, methanotrophic bacteria efficiently reduce the diffusive flux of methane into the water column. In a microcosm study, the resuspension of littoral sediment was simulated in sediment cores for a winter (n = 3) and a summer situation (n = 3). The erosion of surface sediment resulted in a large flux of methane into the overlying water (207 ± 176 μmol h⁻¹ m⁻² in winter and 73 ± 18 μmol h⁻¹ m⁻² in summer). Only a minor part (16 ± 7%) of the methane released was oxidized by methanotrophic bacteria, whereas the major part escaped into the water column. Only 6–16% of the littoral zone has to be resuspended to reach the same flux as from undisturbed littoral sediment. For the daily flux, a sediment resuspension has to last 1–4 h to reach the undisturbed daily flux. The study reveals the important role of sediment resuspension in the littoral methane cycle as an intense but variable source of methane of largely unknown magnitude.     

Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg^-1) and DOC (306 mg kg^-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg^-1), and the bare mudflat was with the lowest content of DOC (270 mg kg^-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg^-1 h^-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg^-1 h^-1) and invertase (9.81mg g^-1 24h^-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg^-1 h^-1), β-glycosidase (2.87 mg kg^-1 h^-1), and invertase (8.02 mg g^-1 24h^-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.     

鄱阳湖苔草湿地甲烷释放特征

2009年5月-2010年4月在鄱阳湖南矶湿地国家级自然保护区选择以灰化苔草为建群种的洲滩,设置土壤-植物系统(TC)、剪除植物地上部分 (TJ)2个试验处理,利用密闭箱-气相色谱法测定了鄱阳湖典型苔草湿地的甲烷(CH₄)释放通量。结果表明:1)TC、TJ 2个试验处理CH₄释放速率变化范围分别为-0.094-17.75 mg · m^-2 · h^-1、-0.122-19.16 mg · m^-2 · h^-1,均表现出明显的季节变化规律;2)地表未淹水期间,剪草处理CH₄释放显著高于非剪草处理(t=2.69, P<0.05);地表淹水达到15 cm后,剪草处理CH₄释放明显低于非剪草处理。3)土壤5 cm温度、土壤水分与2处理非淹水期间CH₄释放速率均呈显著正相关,是非淹水期间CH₄通量变化的主要控制因子,2因子能够共同解释非淹水期苔草湿地65%-74%的CH₄通量变异;4)试验期间,苔草湿地CH₄释放量约为12.77 gC/m²,相当于同期土壤有机质分解碳排放量的4%,甲烷释放的碳消耗不足苔草湿地年NPP的1%。     

Species-specific Effects of Vascular Plants on Carbon Turnover and Methane Emissions from Wetlands

Species composition affects the carbon turnover and the formation and emission of the greenhouse gas methane (CH₄) in wetlands. Here we investigate the individual effects of vascular plant species on the carbon cycling in a wetland ecosystem. We used a novel combination of laboratory methods and controlled environment facilities and studied three different vascular plant species (Eriophorum vaginatum, Carex rostrata and Juncus effusus) collected from the same wetland in southern Sweden. We found distinct differences in the functioning of these wetland sedges in terms of their effects on carbon dioxide (CO₂) and CH₄ fluxes, bubble emission of CH₄, decomposition of ¹⁴C-labelled acetate into ¹⁴CH₄ and ¹⁴CO₂, rhizospheric oxidation of CH₄ to CO₂ and stimulation of methanogenesis through root exudation of substrate (e.g., acetate). The results show that the emission of CH₄ from peat–plant monoliths was highest when the vegetation was dominated by Carex (6.76 mg CH₄ m⁻² h⁻¹) than when it was dominated by Eriophorum (2.38 mg CH₄ m⁻² h⁻¹) or Juncus (2.68 mg CH₄ m⁻² h⁻¹). Furthermore, the CH₄ emission seemed controlled primarily by the degree of rhizospheric CH₄ oxidation which was between 20 and 40% for Carex but >90% for both the other species. Our results point toward a direct and very important linkage between the plant species composition and the functioning of wetland ecosystems and indicate that changes in the species composition may alter important processes relating to controls of and interactions between greenhouse gas fluxes with significant implications for feedback mechanisms in a changing climate as a result.     

西南喀斯特地区轮作旱地土壤CO2通量

中国已承诺大幅降低单位GDP碳排放,农业正面临固碳减排的重任.西南喀斯特地区环境独特,旱地面积占据优势比例,土壤碳循环认识亟待加强.以贵州省开阳县玉米-油菜轮作旱地为研究对象,采用密闭箱-气相色谱法对整个轮作期土壤CO2释放通量进行了观测研究,结果表明:(1)整个轮作期旱地均表现为CO2的释放源.其中油菜生长季土壤CO2通量为(178.8±104.8)mg CO2·m-2·h-1,玉米生长季为(403.0±178.8) mg CO2·m-2·h-1,全年平均通量为(271.1±176.4) mg CO2·m-2·h-1,高于纬度较高地区的农田以及同纬度的次生林和松林;(2)CO2通量日变化同温度呈现显著正相关关系,季节变化与温度呈现显著指数正相关关系,并受土壤湿度的影响,基于大气温度计算得出的Q10为2.02,高于同纬度松林以及低纬度的常绿阔叶林;(3)CO2通量与土壤pH存在显著线性正相关关系,显示出土壤pH是研究区旱地土壤呼吸影响因子之一.     

闽江河口芦苇沼泽和短叶茳芏沼泽生态系统含碳温室气体的年收支

河口感潮沼泽是全球重要的蓝碳生态系统,具有很强的固碳能力。碳收支研究是量化生态系统碳源/汇过程及固碳规模的基础。本研究运用透明箱和不同遮光率布遮盖+红外气体分析仪/气相色谱相结合的方法,模拟不同光照条件,测定闽江河口鳝鱼滩半咸水芦苇沼泽和短叶茳芏沼泽的瞬时净生态系统二氧化碳（CO₂）交换量（net ecosystem exchange,NEE）、生态系统呼吸（ecosystem respiration,ER）以及甲烷（CH₄）排放通量,并通过对总光合吸收量（gross ecosystem exchange,GEE）与光合有效辐射的拟合以及ER与气温的拟合,外推2个沼泽生态系统CO₂气体在月、年尺度上的NEE和ER,评估其年固碳量。2个沼泽生态系统的NEE和ER均具有明显的季节变化,春夏秋季为大气中CO₂的汇,而冬季则转化为大气中CO₂的源,芦苇沼泽年尺度固碳能力显著高于短叶茳芏沼泽。芦苇沼泽与短叶茳芏沼泽CH₄排放通量差异不显著。综合考虑CH₄排放,闽江河口鳝鱼滩半咸水芦苇沼泽、短叶茳芏沼泽生态系统年固碳量分别为（5371.52±336.97） g CO₂-eq/m²和（2730.32±503.67） g CO₂-eq/m²。研究表明：闽江河口半咸水沼泽湿地在年尺度上是一个较强的碳汇,在缓解全球变暖方面发挥着重要的角色。     

Effects of Spartina alterniflora Invasion on Soil Respiration in the Yangtze River Estuary,China

Many studies have found that plant invasion can enhance soil organic carbon (SOC) pools, by increasing net primary production (NPP) and/or decreased soil respiration. While most studies have focused on C input, little attention has been paid to plant invasion effects on soil respiration, especially in wetland ecosystems. Our study examined the effects of Spartina alterniflora invasion on soil respiration and C dynamics in the Yangtze River estuary. The estuary was originally occupied by two native plant species: Phragmites australis in the high tide zone and Scirpus mariqueter in the low tide zone. Mean soil respiration rates were 185.8 and 142.3 mg CO₂ m⁻² h⁻¹ in S. alterniflora and P. australis stands in the high tide zone, and 159.7 and 112.0 mg CO₂ m⁻² h⁻¹ in S. alterniflora and S. mariqueter stands in the low tide zone, respectively. Aboveground NPP (ANPP), SOC, and microbial biomass were also significantly higher in the S. alterniflora stands than in the two native plant stands. S. alterniflora invasion did not significantly change soil inorganic carbon or pH. Our results indicated that enhanced ANPP by S. alterniflora exceeded invasion-induced C loss through soil respiration. This suggests that S. alterniflora invasion into the Yangtze River estuary could strengthen the net C sink of wetlands in the context of global climate change.     

Quantification of methane emissions from Chinese rice fields (Zhejiang Province) as influenced by fertilizer treatment

Methane emissions from rice paddies were quantified by using an automatic field system stationed in Zhejiang Province, one of the centres for rice cultivation in China. The data set showed pronouned interannual variations over 5 consecutive vegetation periods; by computing average values of all experimental plots the annual emissions were 177 g CH₄ m⁻² yr⁻¹ in 1987, 50 g CH₄ m⁻² yr⁻¹ in 1988, and 187 g CH₄ m⁻² yr⁻¹ in 1989. The field preparations encompassed 4 different treatments: (1) no fertilizers, (2) mineral fertilizer (KCl, K₂SO₄), (3) organic manure (rape seeed cake, animal manure), (4) mineral fertilizer plus organic manure. The methane emission rates of the different fertilizer treatments did not show significant differences. The mean emission rates, calculated over the entire observation period of 5 seasons, were 30.4 mg CH₄ m⁻² h⁻¹ (non-fertilized plot) and 28.3 mg CH₄ m⁻² h⁻¹ (mineral fertilizers). These values indicate a high level of methane production even without additional input of organic material into the rice-soils. In the other plots, the organic fertilizers were added once per vegetation period at app. 1 t fresh weight per ha, a relatively low application rate by agronomical standards. The mean emission rates were 35.1 mg CH₄ m⁻² h⁻¹ when manure was applied as sole fertilizer and 27.5 mg CH₄ m⁻² h⁻¹ when applied jointly with potassium fertilizers. Based on the results of this study we estimate a range of 18–28 Tg CH₄ yr⁻¹ as the total methane emission from Chinese rice fields. However, more field data from representative sites in China are needed to reduce the uncertainties in this estimate.     

若尔盖高原沼泽湿地CO2排放时空变化特征

为了更好理解若尔盖高原不同微生境下沼泽湿地生态系统CO₂排放通量的变化特征,以若尔盖高原湿地自然保护区为研究对象,2013和2014年生长季期间,采用了静态箱和快速温室气体法原位观测了3种湿地5种微生境下沼泽湿地CO₂排放通量时空变化规律。结果表明：长期淹水微地貌草丘区湿地（PHK）和洼地区湿地（PHW） CO₂排放通量变化范围分别为38.99-1731.74 mg m^-2 h^-1和46.69-335.22 mg m^-2 h^-1,季节性淹水区微地貌草丘区湿地（SHK）和洼地区湿地（SHW） CO₂排放通量变化范围分别为193.90-2575.60 mg m^-2 h^-1和49.93-1467.45 mg m^-2 h^-1,而两者过渡区的无淹水区沼泽湿地（Lawn） CO₂排放通量变化范围194.20-898.75 mg m^-2 h^-1。相关性分析表明5种微地貌区沼泽湿地CO₂排放通量季节性变化与不同深度土壤温度均存在显著正相关,与水位存在显著负相关（PHW、SHW、SHK、Lawn）或不相关（PHK）,并且水位和温度（5 cm）共同解释了CO₂排放通量季节性变化的87%。3种湿地5种微生境下沼泽湿地CO₂排放通量存在空间变化规律,主要受水位影响,但植物也影响沼泽湿地CO₂排放通量空间变化规律,并且表明沼泽湿地CO₂排放通量与水位平均值存在显著负相关。