Surrounding pressure controlled by water table alters CO2 and CH4 fluxes in the littoral zone of a brackish-water lake |
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| Institution: | 1. National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan;2. Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8572, Japan;3. Department of Environmental Simulation, Institute for Environmental Sciences, 1-7 Obuchi, Rokkasho, Aomori 039-3212, Japan;4. Faculty of Social Sciences, Hosei University, 4342 Aihara, Machida, Tokyo 194-0298, Japan;1. Department of Invasion Ecology, Institute of Botany, The Czech Academy of Sciences, CZ-252 43 Pr?honice, Czech Republic;2. Department of Ecology, Faculty of Science, Charles University in Prague, CZ-128 44 Vini?ná 7, Prague, Czech Republic;3. Department of Botany, Faculty of Science, Charles University in Prague, CZ-128 01 Benátská 2, Prague, Czech Republic;1. Department of Agricultural Sciences, FI-00014 University of Helsinki, Finland;2. Botany Department & Trinity Centre for Biodiversity Research, Trinity College Dublin, Ireland;1. Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, 4888 Shengbeida Road, Changchun 130102, China;2. Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen, 18D, SE-752 36 Uppsala, Sweden;3. Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, 266 Fangzheng Avenue, Chongqing 400714, China;4. School of Environment, Northeast Normal of University, 2555 Jingyue Street, Changchun 130117, China;1. Department of Plant Pathology, Physiology and Weed Science, 435 Old Glade Road, Virginia Tech, Blacksburg, VA 24061, USA;2. Department of Agronomy, Purdue University, West Lafayette, IN 47907, USA;3. Mendel BioEnergy Seeds, Mendel Biotechnology Inc., 3935 Point Eden Way, Hayward, CA 94545, USA |
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| Abstract: | We studied the effect of water table on CO2 and CH4 fluxes at different time scales in the littoral zone of Lake Obuchi, a brackish lake in northern Japan. The vegetation formed three distinct zones along the water table gradient, two dominated by emergent aquatic macrophytes (the Phragmites australis-dominated zone and the Juncus yokoscensis-dominated zone) and one dominated by terrestrial macrophytes (Miscanthus sinensis and Cirsium inundatum-dominated zone). To clarify the impact of variations in water table on monthly and yearly summed CO2 and CH4 fluxes, we examined the relationship between water table and the ratio of observed flux to calculated flux, whereby the calculated flux was based solely on the exponential relationship between flux and soil temperature for each gas. This study revealed that the impact of variations in water table on monthly and yearly summed CO2 and CH4 fluxes differed markedly between the vegetation zones. By taking the temporal change in water table into account in the estimation of both the CO2 and CH4 fluxes, the monthly summed CO2 and CH4 fluxes in the Phragmites-zone were markedly greater in every month of the year compared to estimation based on temperature alone. In the Juncus-zone, the effect of water table on monthly summed CO2 and CH4 fluxes differed between months. In addition, the magnitude of water-table effects controlling monthly summed CO2 and CH4 fluxes differed with atmospheric conditions, i.e., between the pressure-falling and low-pressure phase on the one hand and other pressure phases on the other hand. After weighting all the impacts of temporal changes in water table on fluxes, the yearly summed CO2 and CH4 fluxes showed a 1.26–6.64-fold increase compared with not taking water table effects into account, and the increase differed among the three vegetation zones. |
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