【作者】 孙晓新；

【导师】 牟长城；

【作者基本信息】 东北林业大学 ， 生态学， 2009， 博士

【摘要】 小兴安岭是我国主要山区湿地分布区之一,区内有草丛沼泽、灌丛沼泽和森林沼泽等多种沼泽湿地类型,因此,在我国湿地研究中占有重要地位。本文以小兴安岭山区7种沼泽湿地类型:苔草（Carex schmidtii）沼泽、灌丛（Betula ovalifolia）沼泽、毛赤杨（Alnus sibirica）沼泽、白桦（Betula platyphylla）沼泽、落叶松（Larix gmelinii）-苔草沼泽、落叶松-藓类（moss）沼泽和落叶松-泥炭藓（Sphagnum spp.）沼泽为研究对象,利用静态暗箱-气相色谱法,研究两个生长季内沼泽湿地在自然状态下甲烷排放通量的时间和空间变化规律及其主要影响因素,以及草丛和灌丛沼泽在排水造林干扰、森林沼泽在采伐干扰方式下,沼泽甲烷通量的变化。结果表明:（1）小兴安岭沼泽甲烷通量无统一的日变化规律,且与温度和水位这两个环境因子的相关性较弱。7个沼泽类型中,仅毛赤杨沼泽和白桦沼泽甲烷通量峰值在不同季节出现时间大致相同,且都为单峰曲线;苔草沼泽、灌丛沼泽和落叶松-泥炭藓沼泽甲烷通量的峰值在不同季节出现的时间不同,多数为单峰曲线;落叶松-苔草沼泽和落叶松-藓类沼泽甲烷通量速率较小,多数时间吸收甲烷,没有明显的日变化规律。（2）小兴安岭沼泽甲烷通量的季节排放峰值基本都出现在夏季和秋季,而在春季和秋末,甲烷通量始终较低。温度对沼泽甲烷通量季节变化影响较大,但受到水位的限制,水位较高的沼泽类型甲烷通量的季节变化与温度相关性较好,而水位较低的沼泽类型甲烷通量的季节变化与温度相关性不好。（3）苔草沼泽、灌丛沼泽、毛赤杨沼泽和白桦沼泽的甲烷通量在两个生长季之间的差异较大,2008年生长季平均甲烷通量(19.88-820.22mg·m^-2·d^-1)是2007年(0.64-44.56mg·m^-2·d^-1)的5-31倍;落叶松-泥炭藓沼泽2007年为大气甲烷的较大排放源(56.08mg·m^-2·d^-1),而2008年为大气甲烷的汇(-0.19mg·m^-2·d^-1);而落叶松-苔草沼泽和落叶松-藓类沼泽在两个生长季之间没有显著差异。年际间平均水位的差异,以及年际间水位季节波动的差异,是小兴安岭沼泽甲烷通量年际间差异的主要影响因素。（4）小兴安岭沼泽甲烷通量的空间变异性非常大,苔草沼泽和毛赤杨沼泽为较高的甲烷排放源,落叶松-泥炭藓沼泽、白桦沼泽和灌丛沼泽为较低的甲烷排放源,而落叶松-苔草沼泽和落叶松-藓类沼泽为大气甲烷的弱汇,两个生长季的平均通量依次为:456.63mg·m^-2·d^-1、239.39mg·m^-2·d^-1、26.19mg·m^-2·d^-1、10.86mg·m^-2·d^-1、6.49mg·m^-2·d^-1、-0.69mg·m^-2·d^-1和-1.42mg·m^-2·d^-1。水位和草本植物生物量的差异共同导致小兴安岭沼泽甲烷通量的空间变异性,水位和草本植物生物量较高的地点甲烷通量也较高,相反,水位和草本植物生物量很低的类型甲烷通量较低。温度可能也会对沼泽甲烷空间变化有一定的影响,但作用小于水位和植被。此外,爆发式通量对沼泽甲烷通量空间变化的影响也很大。用草本植物生物量预测不同沼泽类型间甲烷通量的差异,比用乔木和灌木生物量预测的效果好。（5）水位下降时部分沼泽类型（落叶松-泥炭藓沼泽）会产生爆发式通量现象,这对沼泽甲烷通量的日变化、季节变化、年际变化以及空间变化都有较大的影响,同时,也会影响沼泽甲烷通量时空变化规律与环境因子的相关性,因此在观测和估计甲烷通量时不能将其忽略。（6）东北山区沼泽生长季甲烷排放量和年甲烷排放总量分别为1.49 Tg和1.56Tg,为我国天然沼泽甲烷排放量最大的区域。（7）天然沼泽排水造林后,甲烷通量大大降低。天然苔草沼泽和灌丛沼泽为大气甲烷排放源,10年的落叶松人工林仍为甲烷的排放源,但排放量相对较低,为天然灌丛沼泽的约1/3,仅为天然苔草沼泽的约1/50,而20年的落叶松人工林转变为甲烷的汇。人工林内排水沟仍为甲烷排放源,但排放通量大大降低,而造林垄台仅有微弱甲烷排放或转变为甲烷的汇。沼泽排水造林引起的水位下降和维管植物减少是导致甲烷排放量减少的主要原因。排水沟相对面积减少也会导致人工林甲烷排放速率降低。（8）择伐和皆伐都导致3个类型的森林沼泽作为大气甲烷汇的功能降低,或者由大气甲烷的汇转变为甲烷的源。这主要是由于采伐后温度和水位发生变化,二者的共同作用导致采伐后森林沼泽甲烷通量的变化。在有必要对森林沼泽的树木资源进行利用时,为减少甲烷气体的排放,应该尽量避免进行皆伐,只能进行适当的择伐。更多还原

【Abstract】 Wetlands in Xiaoxing’an Mountains, which one of the main mountainous wetlands distribution areas, play an important role of the wetlands study in China, because of the diversity wetland types including marshes, thicket swamps and forested swamps. We observed the methane fluxes from seven types of wetlands in Xiaoxing’an Mountains including a marsh （M）, a thicket swamp （TS）, a Alnus sibirica swamp （FS-1）, a Betula platyphylla swamp （FS-2）, a Larix gmelinii - Carex schmidtii swamp （FS-3）, a Larix gmelinii - moss swamp （FF） and a Larix gmelinii - Sphagnum spp. swamp （FB）, their spatial and temporal variations of methane fluxes and the affecting factors, in the growing seasons of 2007 and 2008 using the static opaque chamber and gas chromatography technique. Also the methane fluxes under the anthropogenic disturbances of draining for forestation, and cutting were measured. Results showed that:（1） No common diurnal variations were found in all the wetlands, and the diurnal patterns were weakly correlated to temperatures and water tables. FS-1 and FS-2 have the same pattern of diurnal fluxes with unique peaks at the same time in difference seasons. M, TS and FB have the patterns of diurnal fluxes with unique peaks at different time in difference seasons. No apparent diurnal variations were observed in FS-3 and FF because of the low flux rates.（2） Most of methane fluxes from wetlands in Xiaoxing’an Mountains in the growing season peaked in summer or autumn, but the rates kept at low levels in spring or late autumn. Seasonal variations of methane fluxes were correlated with temperatures, but the relationships were restricted by water wables. Seasonal variations of methane fluxes were correlated well with temperatures when wetlands water tables were high but the relationships were weak when water tables were low.（3） Interannual variations of methane fluxes were large in M, TS, FS-1 and FS-2 in the two growing seasons, mean methane fluxes in the growing season of 2008(19.88-820.22mg·m^-2·d^-1) were 5-31 times larger than the mean values of 2007(0.64-44.56mg·m^-2·d^-1). FB was an atmospheric methane source in the growing of 2007(56.08mg·m^-2·d^-1) but a sink in the same periods of 2008(-0.19mg·m^-2·d^-1). No significant differences of methane fluxes in the growing season of 2007 and 2008 in FS-3 and FB. Interannual variations of methane fluxes were controlled by the mean annual water table and the variations of water table fluctuations.（4） Apparent spatial variations of methane fluxes from wetlands in Xiaoxing’an Mountains were observed. M and FS-1 were big sources of atmospheric methane, FB, FS-2 and TS were small sources, but FS-3 and FF were weak sinks, and the average methane emission rates during the two growing seasons were 456.63mg·m^-2·d^-1, 239.39mg·m^-2·d^-1, 26.19mg·m^-2·d^-1, 10.86mg·m^-2·d^-1, 6.49mg·m^-2·d^-1,-0.69mg·m^-2·d^-1 and -1.42mg·m^-2·d^-1, respectively. Water table and aboveground herb biomass together controlled the spatial variations of methane fluxes. Seasonal average methane fluxes were high with higher water table and herb biomass but low with lower water table and herb biomass. Air temperature may contribute less to the spatial variations of methane fluxes from wetlands than water table and herb biomass. Episodic fluxes may contribute large to the spatial variations of methane fluxes from wetlands.Herbs are better indicators of methen flux rates from a region scale than shrubs or trees.（5） Episodic fluxes were detected in FB when water table falling, which greatly influenced the diurnal, seasonal, interannual and spatial variations of methane fluxes, also the correlations of methane fluxes and the affecting factors. It was important to understanding and evaluating the regional methane fluxes, so should not be overlooked.（6） Based on the in situ measurement, we preliminarily estimated the budget of methane emissions from wetlands in mountainous regions in Northeast China was 1.49Tg in the growing season and 1.56Tg in the year. Wetlands in mountainous regions of northeast China were likely to be the biggest sources of atmospheric methane from natural wetlands in China.（7） Methane fluxes decreased greatly after natural wetlands were drained for forestation. Natural M and TS were atmospheric methane sources, also were 10- years-old plantations, but the flux rates were only 1/3 and 1/50 as those from M and TS, respectively. 20- years-old plantations change to the atmospheric methane sink. Draining ditches in the plantations were atmospheric methane sources, however, flux rates decreased greatly. But planting ridges were weak sources or changed to the sinks. Water table lowering and vascular plants decreasing mainly contributed to the decrease of methane emission rates after wetlands draining for forestation. The decrease of draining ditches area may also cause methane emission rates decreasing in the plantations.（8） Three forested swamps after selective and clear cutting uptakes less methane than the natural ones, or changed to the atmospheric methane sinks. Changes in temperature and water table together contributed to the changes of methane fluxes after cutting. If the utilization of trees in forested swamps were necessary, we should choose selective cutting rather than clear cutting to reduce methane emission.更多还原