【作者】 王晓龙；

【导师】 张社奇； 郑循华；

【作者基本信息】 西北农林科技大学 ， 生物物理学， 2015， 硕士

【摘要】 甲烷(CH4)是仅次于二氧化碳的重要温室气体,其在百年尺度上的增温潜势是二氧化碳的28倍,其源和汇机理的认知引起重要关注。高寒泥炭湿地是重要的大气甲烷排放源,但由于高寒湿地非生长季的气候条件极其恶劣,过去的原位观测研究大多集中在生长季,致使迄今仍对季节性冻土区高寒泥炭湿地尤其是非生长季CH4排放缺乏充分认识。本研究以地处青藏高原东北部的若尔盖地区典型湿地为例,采用静态暗箱-气相色谱人工观测方法,开展了跨越冬、春季和初夏季连续9个月的原位观测研究,试图了解该湿地CH4排放特征及非生长季排放的相对重要性。结果与初步结论如下:1)整个观测期间湿地通量平均值介于0.1~1.0 mg C m-2 h-1之间;2)该湿地在非生长季也有较强的CH4排放,且非生长季CH4通量的温度响应系数Q10(18.1~29.8)远远大于在生长季(1.4~2.2),这意味着非生长季的CH4排放对气候变暖更敏感得多;3)结合其他生长季的观测结果,对观测数据的外推估计,该湿地的CH4年排放量约为30 kg C ha-1 yr-1,其中非生长季的贡献率高达50%以上;4)观测期的CH4通量具有明显季节变化,可解释为温度季节变化、土壤冻结与消融过程、水位(或土壤湿度)季节动态和植物生长节律等共同作用的结果;5)观测期的CH4通量还在构成湿地景观的三种微地形之间呈现出显著差异,即凸起处的排放相对最弱,凹陷处居中,二者的过渡带相对最强(p<0.01),它们对整个湿地排放量的贡献率依次估计为大约22%、35%和43%,这种空间差异性可解释为水位(或土壤湿度)、植物分布和土壤有机质含量等因素的空间差异所致。不过,本研究中原位观测的持续时间相对较短,因而上述结果或结论能否在年度或更长时间尺度上重现,还需要长期连续观测研究加以检验。更多还原

【Abstract】 Methane(CH4) is the second important greenhouse gas after carbon dioxide, which have 28 times global warming potential(GWP) of CO2 on the scale of one hundred years. More attention should be paid to the acknowledgement of its source and sink. Alpine peat wetlands are important sources of atmosphere methane. Most of available in situ measurements were exclusively done in growing seasons because of very weathers in non-growing seasons. Due to this situation, CH4 emission from seasonal-freezing alpine peat wetlands in non-growing season so far has not been well known. This study aimed at investigation of the CH4 emission characteristics and its importance in the non-growing season by carrying out 9-mouth field measurements(from almost entire winter through early summer) in a Zoige alpine wetlands with seasonal-freezing peat. The field site was located at the northeast edge of the Qinghai-Tibetan Plateau. Methane fluxes were manually measured weekly or half-weekly at 9:00~11:00 in the morning at 6 random locations, with typical bulge(BA), hollow(HA) and transition(TA) areas for each, using static opaque chambers to collect gas samples and a gas chromatograph for immediate sample analysis.The CH4 fluxes during the whole observation period, mean methane emissions rate, among 6 spatial redundancies, ranged from 0.1 to 1.0 mg C m-2 h-1 showing significant emission in the non-growing season. The temperature sensitivity(Q10, which is the folds of changes in CH4 fluxes due to a temperature change of 10oC) during the non-growing period(18.1~29.8) was much higher than that during the growing season(1.4~2.2), implicating that the methane emission in non-growing seasons could be much more sensitive to climate warming. By simply extrapolating our measured fluxes, combined with results of other observations in growing season, the annual CH4 emission from the investigated alpine wetland was estimated at about 30 kg C ha-1 yr-1, of which at least 50% was released in the non-growing season. The CH4 fluxes during the observation period showed significant seasonal variation, which may be attributed jointly to temperature variation, freezing-thawing alternation, water table(or soil moisture) dynamics and seasonality of plant growth. The CH4 fluxes were also significantly different among the micro-landforms, with statistically the lowest, highest and moderate values at the BA, TA and HA, respectively(p < 0.01). The BA, TA and HA approximately accounted for 22%, 43% and 35% of the bulk CH4 emission from the whole wetland. Such spatial variability may be attributed to the spatial variations in environment factors such as water table(or soil moisture), plant distribution and soil organic matter content.However, the above results and conclusions derived from our field measurements during a relatively short period still need further confirmation with long-term field observations lasting for years or even longer.更多还原