The interactive effects of elevated carbon dioxide and water table draw-down on carbon cycling in a Welsh ombrotrophic bog |
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| Authors: | T. Ellis P.W. Hill N. Fenner G.G. Williams D. Godbold C. Freeman |
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| Affiliation: | 1. School of Biological Sciences, Bangor University, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK;2. School of the Environment and Natural Resources, Bangor University, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK;1. Aarhus University, Department of Bioscience, Silkeborg, Denmark;2. Aarhus University, Department of Agroecology, Tjele, Denmark;1. Key Laboratory for Subtropical Mountain Ecology, School of Geographical Science, Fujian Normal University, Fuzhou 350007, China;2. Institute for Pacific Islands Forestry, USDA Forest Service, Hilo, HI 96720, USA;3. College of Agriculture, Forestry and Natural Resource Management, University of Hawaii, Hilo, HI 96720, USA;1. Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745 Jena, Germany;2. Department of Hydrogeology, Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany;3. Department of Aquatic Geomicrobiology, Institute of Ecology, Friedrich Schiller University Jena, Jena, Germany;4. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany;5. Institute for Inorganic and Analytical Chemistry, Bioorganic Analytics, Department of Chemistry and Earth Sciences, Friedrich-Schiller-Universität, Lessingstr. 8, 07743 Jena, Germany;6. Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07745 Jena, Germany;1. Bangor Wetlands Group, The Wolfson Carbon Capture Laboratory, School of Biological Sciences, Bangor University, Deiniol Road, Bangor, Gwynedd, LL57 2UW, United Kingdom;2. Institute of Biology, University of Bialystok, Cio?kowskiego 1J, 15-245 Bia?ystok, Poland;1. College of Agronomy, Northwest A&F University, Yangling, 712100 Shaanxi, China;2. The Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling, 712100 Shaanxi, China;3. College of Urban and Environmental Science, Northwest University, Xi''an 710072, Shaanxi, China;4. Department of Microbiology and Plant Biology, University of Oklahoma, Norman 73019, OK, USA;5. Center for Ecological and Environmental Sciences, Key Laboratory for Space Bioscience & Biotechnology, Northwestern Polytechnical University, Xi''an 710072, Shaanxi, China;1. Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark;2. Technical University of Denmark, Department for Chemical and Biochemical Engineering, Frederiksborgvej 399, DK-4000 Roskilde, Denmark;3. Department of Biology, Microbial Ecology, Lund University, Sölvegatan 37, 223 62 Lund, Sweden |
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| Abstract: | The effects of elevated atmospheric CO2 (eCO2) and water table draw-down on soil carbon sequestration in an ombrotrophic bog ecosystem were examined. Peat monoliths (11 cm diameter, 25 cm deep) with intact bog vegetation were exposed to ambient or elevated (ambient + 200 mg l?1) atmospheric CO2, combined with a natural water table (level with the peat surface) or a water table draw-down (?5 cm). Eight observations per treatment were included in the study, which was conducted over a 12 week period. Concentration of dissolved organic carbon (DOC), phenolic compounds and the fluxes of CO2 and CH4 were measured. The eCO2 treatment caused an increase in the CH4 and CO2 fluxes and a small decrease in both the DOC and phenolic concentrations. The water table draw-down invoked decreases in phenolic and DOC concentrations, a decrease in CH4 flux and a small increase in CO2 flux. The combined (eCO2 + water table draw-down) treatment caused a larger than expected CH4 flux decrease and CO2 flux increase and an increase in DOC concentration. Our results suggest very different effects on the system dependent on the treatment applied. The draw-down treatment principally increased oxidation of the rhizosphere resulting in increased decomposition and as such a removal of material from the dissolved carbon pool. The data also suggest labile carbon availability may be limiting the rate of decomposition and so slowing inorganic nutrient and carbon pool turn-over. The elevated CO2 addressed the labile-carbon limitation. Under the environment of the combined treatment, these limitations were effectively removed, culminating in a destabilisation of the carbon-sequestering environment to a weaker sink (or even a source) of atmospheric carbon. |
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