Acidity controls on dissolved organic carbon mobility in organic soils |
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Authors: | Chris D. Evans Tim G. Jones Annette Burden Nick Ostle Piotr Zieliński Mark D. A. Cooper Mike Peacock Joanna M. Clark Filip Oulehle David Cooper Chris Freeman |
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Affiliation: | 1. Centre for Ecology and Hydrology, Environment Centre Wales, , Bangor, LL57 2UW UK;2. School of Biological Sciences, Bangor University, , Bangor, Gwynedd, LL57 2UW UK;3. Centre for Ecology and Hydrology, Lancaster University, , Lancaster, LA1 4AP UK;4. Institute of Biology, University of Bialystok, , Bialystok, 15‐950 Poland;5. Soils Research Centre, Department of Geography and Environmental Science, University of Reading, , Reading, RG6 6DW UK;6. Global Change Research Centre AS CR, , Brno, 603 00 Czech Republic |
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Abstract: | Dissolved organic carbon (DOC) concentrations in surface waters have increased across much of Europe and North America, with implications for the terrestrial carbon balance, aquatic ecosystem functioning, water treatment costs and human health. Over the past decade, many hypotheses have been put forward to explain this phenomenon, from changing climate and land management to eutrophication and acid deposition. Resolution of this debate has been hindered by a reliance on correlative analyses of time series data, and a lack of robust experimental testing of proposed mechanisms. In a 4 year, four‐site replicated field experiment involving both acidifying and deacidifying treatments, we tested the hypothesis that DOC leaching was previously suppressed by high levels of soil acidity in peat and organo‐mineral soils, and therefore that observed DOC increases a consequence of decreasing soil acidity. We observed a consistent, positive relationship between DOC and acidity change at all sites. Responses were described by similar hyperbolic relationships between standardized changes in DOC and hydrogen ion concentrations at all sites, suggesting potentially general applicability. These relationships explained a substantial proportion of observed changes in peak DOC concentrations in nearby monitoring streams, and application to a UK‐wide upland soil pH dataset suggests that recovery from acidification alone could have led to soil solution DOC increases in the range 46–126% by habitat type since 1978. Our findings raise the possibility that changing soil acidity may have wider impacts on ecosystem carbon balances. Decreasing sulphur deposition may be accelerating terrestrial carbon loss, and returning surface waters to a natural, high‐DOC condition. |
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Keywords: | acidity dissolved organic carbon organic soil peat podzol soil carbon sulphur |
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