若尔盖高原花湖湖滨湿地甲烷排放研究

若尔盖高原湿地位于青藏高原东北部地区，平均海拔3,400-3,600m，是长江和黄河的自然分水区，区内发育了大面积的草本沼泽以及高寒沼泽化草甸、高寒湖泊。由于它所处的位置海拔高、气候波动较大，并处于我国三大自然区的交错过渡带，因而被认为是我国最为典型的脆弱湿地生态系统之一。由于地处偏远、自然环境条件恶劣等多方面的原因，针对若尔盖湿地的科学研究资料一直以来还非常缺乏。本文对国内外近年来在湿地生态系统甲烷排放过程、研究方法，以及关于湿地生态系统甲烷排放的影响因素进行了综述，并采用静态箱－气相色谱法，从湿地环境格局、湿地甲烷排放等方面，对若尔盖高原典型高寒湖泊湖滨不同类型湿地甲烷排放特征进行了研究，并进一步探讨了影响若尔盖高原高寒湖泊湖滨带甲烷排放的因素。得到如下结果：1．若尔盖高原花湖湖滨湿地在植物生长季（6 至8 月），甲烷排放平均速率为0.315 mg·m-2·h-1；不同月份间甲烷排放速率存在差异，分别为：-0.054、0.471、0.493 mg·m-2·h-1。不同类型湿地甲烷排放速率亦表现出差异，两栖蓼（Polygonum amphibium）湿地、滩涂和藏嵩草（Kobresia tibetica）草甸甲烷排放速率分别为：0.464、0.477、0.005mg·m-2·h-1。2．若尔盖高原花湖湖滨湿地甲烷排放速率与土壤10cm 温度显著相关。土壤温度是影响若尔盖高原花湖湖滨不同类型湿地甲烷排放的重要因素之一。随着土壤温度的升高，土壤微生物活性增强，使土壤中的氧消耗加快，氧化还原电位下降，有利于产甲烷菌的生长，从而增加土壤的甲烷产生量。3．地表水位与若尔盖高原花湖湖滨湿地甲烷排放速率相关性不显著。地表水覆盖，使得湿地土壤缺氧状况得到加强，增强了土壤中产甲烷菌的活性，促进甲烷形成，再通过植物、气泡或扩散的形式释放出土壤。但水层的加深，也使土壤中已产生的甲烷在通过气泡或扩散形式穿越水层时，被氧化的量增加，从而减少了甲烷向大气中的排放。4．植被高度以及植被地上生物量与若尔盖高原花湖湖滨带甲烷排放速率的相关性不显著。植物主要通过凋落物以及根系分泌物的输入为产甲烷菌提供基质，并作为土壤与大气之间的甲烷气体交换的传输途径；与其他环境因素共同影响湿地生态系统甲烷排放。The Zoige wetland on the eastern fringe of Qinghai-Tibetan Plateau, with averagealtitude between 3,400 and 3,600m, is the watershed of Yangtze River and YellowRiver. There are large area of peatland, subalpine meadow and lakes in this region.Due to its high elevation, transitional topology and high fluctuation of climate, theZoige wetlands represent one of the most fragile wetland ecosystems in China. And asa result of remote location and harsh environment conditions, the researches on theZoige wetland are relatively rare, especially the researches on the methane emissionfrom littoral zone of alpine lakes. Variations of methane emission rates as measuredby the method of static chamber – gas chromatography (GC) were detected fromlittoral zone of alpine lake on the Zoige Plateau. Relationships between methaneemission rates and environmental factors were analyzed. It is concluded that:1．The average methane emission rate in the littoral zone of Huahu Lake, ZoigePlateau is 0.315 mg·m-2·h-1, with evident spatial and temporal variations. The littoralzone has different methane effluxes with -0.054, 0.471, and 0.493 mg·CH4·m-2·h-1in June, July and August respectively. Different types of wetland have differentmethane emission rates, with value of 0.464, 0.477, and 0.005 mg·CH4·m-2·h-1 forPolygonum amphibium wetland ( PA ), Shoal ( S ) and Kobresi tibetica meadow ( KT ), respectively.2． The soil temperature at 10cm is significantly correlated with the methane effluxesin littoral zone of Huahu Lake, Zoige Plateau, and which is one of the most important factors influencing the methane emission from this region. The activities of soilmicroorganisms rise under higher soil temperature and increases oxygen consumptionand decreases Eh, which is in favor of the methanogensis, and enhances theproduction of methane in soil.3． The correlation between the standing water and methane effluxes from littoralzone of Huahu Lake is not significant. Because of the standing water, the anaerobicconditions of wetland soil have been enhanced, and are favor to the decomposition oforganic matter. And the anaerobic conditions strengthen the methanogensis’ activities,thus the methane production, which release to the atmosphere by diffusion, ebullitionand aerenchymal plants. With the water level’s increase, more methane produced insoil which is transferred by ebullitions or diffusion are oxidated, thus reduce themethane release to the atmosphere.4． The height and aboveground biomass of vegetation are not significant related tothe methane effluxes from littoral zone of Huahu Lake, Zoige Plateau. The vegetationprovides substrates for methanogensis by litter and root exudates; act as thetransportation way of methane between soil and atmosphere; influence the methaneemission of wetland ecosystems with other environment factors.

Controls on suppression of methane flux from a peat bog subjected to simulated acid rain sulfate deposition

The effect of acid rain SO42− deposition on peatland CH4 emissions was examined by manipulating SO42− inputs to a pristine raised peat bog in northern Scotland. Weekly pulses of dissolved Na2SO4 were applied to the bog over two years in doses of 25, 50, and 100 kg S ha−1 yr−1, reflecting the range of pollutant S deposition loads experienced in acid rain-impacted regions of the world. CH4 fluxes were measured at regular intervals using a static chamber/gas chromatographic flame ionization detector method. Total emissions of CH4 were reduced by between 21 and 42% relative to controls, although no significant differences were observed between treatments. Estimated total annual fluxes during the second year of the experiment were 16.6 g m−2 from the controls and (in order of increasing SO42− dose size) 10.7, 13.2, and 9.8 g m−2 from the three SO42− treatments, respectively. The relative extent of CH4 flux suppression varied with changes in both peat temperature and peat water table with the largest suppression during cool periods and episodes of falling water table. Our findings suggest that low doses of SO42− at deposition rates commonly experienced in areas impacted by acid rain, may significantly affect CH4 emissions from wetlands in affected areas. We propose that SO42− from acid rain can stimulate sulfate-reducing bacteria into a population capable of outcompeting methanogens for substrates. We further propose that this microbially mediated interaction may have a significant current and future effect on the contribution of northern peatlands to the global methane budget.