中国滨海湿地CH4通量研究进展

滨海湿地严格的厌氧环境造成与其面积不成比例的碳储量,同时有利于CH₄的产生。探讨滨海湿地温室气体通量,尤其是CH₄通量,对确定滨海湿地究竟是温室气体的“源”还是“汇”,评估滨海湿地对全球变化的影响具有重要的作用。论文通过对中国滨海湿地CH₄通量的排放机制、时空变化以及影响因素进行阐述总结得出：闽江河口CH₄通量明显大于长江口和黄河口,主要原因在于温度和生物量的差异;江苏滨海湿地CH₄通量的研究相对薄弱,南方红树林湿地CH₄通量的空间差异较大。潮汐对滨海湿地CH₄通量的影响呈“M”型：涨潮开始时,CH₄通量逐渐增加,随着水位的加深,逐渐减少;当落潮到最适宜产生CH₄的水位深度时,大量原先产生的CH₄开始排放出来,待水位继续下降,产生的CH₄极容易被氧化,开始减少。目前缺乏研究滨海湿地CH₄通量的标准方法,而且针对潮汐变化,微生物以及酶活性对CH₄排放的影响研究比较薄弱,在此基础上,提出了利用箱法进行CH₄通量的研究需因地制宜,依据研究目的以及植被、土壤、水文的差异选择不同的样点布设原则和采样方法。

Advances in the Research on Methane Emissions of Coastal Saline Wetlands in China

Methane is mainly produced by methanogenesis under anaerobic conditions, oxidized by methanotrophic bacteria under aerobic environment, and transported to atmosphere by diffusion, ebullition and aerenchyma of plants. Coastal saline wetlands store large proportion of carbon compared to the other ecosystems, and become a significant source of atmosphere CH4 due to the anaerobic environment. Coastal wetlands are characterized by high temporal and spatial variations of methane emission due to topographic feature, vegetation cover and astronomic tidal fluctuation, resulting in the difficulty in the field sampling of greenhouse gas, especially methane flux which is sensitive to global climate change. Consequently, it’s urgent to comprehensively investigate and review the methane emission in the coastal wetlands in order to accurately evaluate the contribution of coastal wetlands to global warming. The mechanism, spatial-temporal variations and controlling environment factors of CH4 emissions were summarized in this paper. We may safely draw the conclusion that the mean CH4 emissions from Minjiang River estuary were higher than those from Yangtze River estuary and Jiangsu coastal saline wetland. The average CH4 fluxes in spring, summer, autumn and winter were -0.0109, -0.0174, -0.0141 and -0.0089 mg CH4?m-2?h-1, indicating that the coastal marsh in Yellow River estuary acted as CH4 sink. In addition, significant differences existed among different tidal flats in Mangrove in South China. The effect of tidal fluctuation on CH4 emission presented to be a trend of “M”. When the tide rises, the CH4 fluxes firstly increase, and then begin to decrease with the increasing of tidal water. Later when the tide ebbs, the CH4 emit to the atmosphere obviously increase due to high abundant of produced CH4 in the spring tide. When the tide falls below the surface soil, CH4 is easily oxidized and so its flux decreased. However, there existed some problems we need to solve: 1) lacking of the standard system of the research method; 2) lacking of the research on the effect of microorganism and microbial enzymes on the CH4 emission; 3) strengthening the studies of effects of flood and ebb on the CH4 emission. Finally, we proposed the principles and methods of sampling when chamber was used to collect the gas sampling, which uses different sampling frequency, and samples at different site layouts according to the research objects and the variations of vegetation, soil, and hydrology in the coastal wetlands.