【作者】 孟祥楠；

【导师】 赵雨森； 倪红伟；

【作者基本信息】 东北林业大学 ， 水土保持与荒漠化防治， 2012， 博士

【摘要】 湿地是陆地上巨大的有机碳储库,也是温室气体甲烷的重要来源。三江平原是我国最大的淡水沼泽湿地分布区,受全球变化和人为的原因,水文条件发生改变,植被发生变化。因此在这种背景下,本文主要研究了三江平原湿地生态序列温室气体排放(CO2、CH4、N2O)的动态变化特征,进而分析不同群落三江平原湿地碳汇功能和全球增温潜势的变化趋势。随着微地形和水分条件的变化,从环形湿地的边缘到中心,群落由典型草甸逐渐变化为沼泽化草甸和沼泽。不同群落小气候发生动态变化,随着水分的增加,群落内各层次综合表现为温度逐渐降低、湿度逐渐上升和光照强度先降低后升高再降低的趋势,不同层次小气候的变化规律和变化幅度不同。随着水分的增加,TER显著降低。不同群落TER的季节变化基本一致,表现为单峰模式,TER月均值最大值为1112.61mg·m-2-h-1。由于气温、降水等因素的影响,TER有着明显的年际变化,生长季累计排放量最大值为31.99t·ha-1。TER日变化规律与温度一致,表现为单峰模式。土壤呼吸的分布特征与季节变化趋势与TER基本一致,日变化趋势略有差异。土壤中的CO2平均浓度为2092ppm,不同群落土层中CO2浓度总体呈上升趋势,并且随着土层位置的加深,CO2浓度逐渐升高。TER与温度和水深之间的关系分别表现为显著指数相关和对数负相关关系。随着水分的增加,生态系统CH4排放通量显著升高,并且存在明显的季节变化和年际变化,CH4月均值最大值为72.00mg·m·2·h-1,生长季累计排放量最大值为2296.11kg·ha-1。不同群落的日变化规律存在差异,影响因素比较复杂。土壤CH4排放通量的分布特征与生态系统CH4排放基本一致,但各群落差异显著性下降,并且通量值要小于生态系统CH4通量值,说明植物对CH4的传输作用很强。三江平原湿地土壤中的CH4浓度比较大,平均为217.95ppm,不同群落土壤中CH4浓度逐渐增大。生态系统CH4排放通量与温度和水深之间的关系分别表现为显著指数相关和对数正相关关系。三江平原湿地是N2O的弱排放源,不同群落差异不明显,峰值多出现在前两个群落,月均值最大值为0.145mg·m-2·h-1生长季累计排放量最大值为3.90kg·ha-1,位于环形湿地中心的几个群落生态系统N2O通量较低,甚至出现了负值,表现为弱吸收。N2O通量季节变化和年际变化差异不显著,并且无明显的日变化规律。土壤N2O通量略小于与生态系统N2O通量,变化规律基本一致。三江平原湿地土壤中的N2O浓度平均为327.86ppb。生态系统N2O排放通量与温度和水深分别呈正负线性相关,但相关性较低。三江平原湿地整个生态序列NEE值为-17.47～-4.78t·ha-1,表现为CO2净吸收。各群落均表现为对碳的净固定,净碳交换量为-0.87～-4.51t·ha-1,并且随着水分的增加,碳汇功能先减小后增大,与NEE的变化规律一致。从20～500a的时间尺度上,三江平原湿地生态序列整体上均表现为随着水分的增加,增温潜力逐渐增大,不同群落GWP的大小主要取决于CH4的排放和CO2的净固定。随着时间尺度的延长,三种温室气体的综合增温潜势开始下降,其中CH4的增温潜势下降最为明显,随着CH4温室效应的减弱,三江平原湿地生态系统从增强全球增温潜势逐渐变化成为抑制全球增温潜势。更多还原

【Abstract】 The wetland is a huge organic carbon pool and also an important emission source of greenhouse gas CH4. Sanjiang Plain is the largest distribution area of fresh water marsh wetland in China. Due to global climate change and multiple artificial interference, there were great changes in the hydrological conditions and vegetation Succession in the wetland. Therefore, this paper mainly studied the characteristics of greenhouse gases emissions and analyzed the carbon sink function and the change of global warming potential in different successional stages in Sanjiang Plain wetlands.With the changes of microtopography and moisture conditions, vegetation succession occurred from typical meadow and swamp meadow in the edge of the ring wetland to swamp communities in the center wetland. Microclimate climate was changed dynamically in different successional stages. With succession proceeding, temperature decreased and humidity increased gradually. The light intensity had a changing trend of first decrease and then increase and further decrease. There were significant difference in the changing trends and intensities for the different levels of microclimate climates.With succession proceeding, TER was reduced significantly. The seasonal variations of TER in different successional stages show a single peak pattern, with the maximum monthly averaged values of1112.61mg-m"2-h-1. TER has obvious interannual changes due to the impact of environmental factors such as temperature and precipitation. In the growing season, maximum cumulative emissions was31.99t-ha-1. The diurnal variation of both TER and temperature showed a single peak pattern. Distribution characteristics and seasonal trends of TER was consistent with that of soil respiration, with a slight difference in diurnal variation. The average concentration of CO2in the soil was2092ppm. In different successional stages, soil CO2concentration was gradually increased with the increasing soil layer. There was a significant exponential relationship between the TER and temperature and logarithmic negative relationship between the TER and water depth.With succession proceeding, CH4flux showed obvious seasonal and interannual variation. The maximum monthly averaged values of CH4flux was72.00mg-m-2·h-1. In growing season, maximum cumulative emissions was2296.11kg·ha-1. There were significant differences in diurnal variation of CH4flux of the wetlands in different succession stages; the impact factors were more complex. Distribution characteristics and seasonal trends of soil CH4flux were consistent with that of the ecosystem CH4flux, but the significance was decreased. The CH4flux of soil was less than CH4flux of, it show that plant has strong shuttle effect for CH4. The average concentration of CH4in the soil was217.95ppm. Soil CH4concentration of different successional stages gradually increased with the increasing soil layer. There was a significant exponential relationship between the CH4flux and temperature and a logarithmic positive correlation between the CH4flux and water depth.Sanjiang Plain wetland was a weak emission source for N2O and there was no significant difference in N2O emission between different successional stages. The maximum emission often occurred at the first two successional stages, with the maximum monthly averaged value of0.145mg·m-2·h-1. In growing season, maximum cumulative emission of N2O was3.90kg·ha-1. The N2O flux was lower in the center of the ring wetlands, or even negative emission, showing a weak absorption. The seasonal, interannual and diurnal variability of N2O fluxes was not significant. Soil N2O fluxes were slightly less than the ecosystem N2O fluxes, with a consistent variation trend. The average concentration of N2O fluxes in the soil was327.86ppb. Ecosystem N2O emission flux was positive and negative linear correlation with temperature and water depth, respectively, but with a low correlation.NEE of Sanjiang Plain wetland ranged from-17.47to-4.78t-ha-1in different succession stages, showing the net uptake of CO2. In the whole successional stages, the wetland showed a net fixed carbon, with the amount of net carbon exchange of-0.87～-4.51t-ha-1, and the carbon sink function was firstly decreased and then increased with the sucession, showing a similar change with that of NEE. From20～500a time scale, GWP in Sanjiang Plain wetland was increased gradually with succession proceeding. GWP in the different successional stages mainly depends on the CH4emissions and the net fixed CO2. With the extension of the time scale, the warming potential of the three greenhouse gases began to decline, of which the warming potential of CH4showed the most obvious decline. As CH4greenhouse effect is weakened gradually, global warming potential was also decreased gradually.更多还原