In this study we determined the magnitude of plant mediated CH4 emission (flux) in two vegetation types of Carex ramenskii. The objectives of this paper were to quantify the proportion of CH4 emissions from plant mediated flux and the total flux (plant and soil). This information is needed in order to understand how grazing affects plant mediated CH4 flux. In addition, we differentiated between two vegetation morphs, grazed and ungrazed, and determined the plant mediated CH4 flux for vegetation type.  This study was conducted at a field site on the Tutakoke River (61 15’N, 165 30’W) which is located in the coastal region of the Yukon-Kuskokwim Delta. Three replicate plots of the two vegetation morphs of Carex ramenskii were established. Methane flux was measured with a total flux chamber (plant and soil) and a single leaf chamber using a Picarro Cavity Ring-Down Spectroscopy Analyzer (Model G2308, Picarro Inc., Santa Clara, California). Plant density for the two plant types was determined. Temperature measurements were taken and correlated with gas flux. This study found that total net CH4 emissions from Carex ssp. were the same in both vegetation types. This similarity could indicate that plant mediated flux through vegetation is not affected by grazing in the sense that grazing is neither facilitating nor inhibiting plant mediated CH4 flux. The magnitude of plant mediated flux was still greater in the ungrazed meadow type, indicating on both greater facilitation of CH4 flux, and below ground oxygen transport enabling higher rates of CH4 consumption.

Plants (macrophytes) growing in lake and wetland sediments are known mediators of greenhouse gases (GHG), specifically methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O). Current studies have emphasized the potential risk of underestimation regarding emissions of plant-mediated GHGs from terrestrial systems including lakes, streams and other freshwater bodies. In order to differentiate the possible sources and sinks of atmospheric carbon and nitrogen in aquatic environments, this study aims to investigate the spatial variability of GHG fluxes in stands of common wetland macrophytes. Field samplings were carried out in the summer of 2012 where 24-hour diel measurements were conducted with the static chamber method in a boreal lake in south western Sweden. Two macrophyte communities were studied; one mixed-species stand and one species-specific stand of water horsetail (Equisetum fluviatile). Spatial variability was confirmed at several stages, both between and within stands. The species-specific stand emitted more CH4 than the mixed stand, from 0.17 to 8.99 mmol m-2 h-1, compared to 0.63 – 1.95 mmol m-2 h-1 maximum measured. Within stand variability was confirmed as variable CH4 flux per strand of E. fluviatile was established. No significant differences were observed regarding CO2 and N2O, other than weak correlation in diel patterns, e.g. daytime uptake and night time respiration/emission for both gases.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22630号 / 理博第4619号 / 新制||理||1664(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 中野 伸一, 教授 酒井 章子, 教授 曽田 貞滋 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM