Publication Date:
2014-10-08
Description:
Freshwater marshes are well-known for their ecological functions in carbon sequestration, but complete carbon budgets that include both methane (CH 4 ) and lateral carbon fluxes for these ecosystems are rarely available. To the best of our knowledge, this is the first full carbon balance for a freshwater marsh where vertical gaseous (carbon dioxide (CO 2 ) and CH 4 ) and lateral hydrologic fluxes (dissolved and particulate organic carbon) have been simultaneously measured for multiple years (2011-2013). Carbon accumulation in the sediments suggested that the marsh was a long-term carbon sink and accumulated ~96.9±10.3 (±95% CI) g C m −2 yr −1 during the last ~50 years. However, abnormal climate conditions in the last three years turned the marsh to a source of carbon (42.7±23.4 g C m −2 yr −1 ). Gross ecosystem production and ecosystem respiration were the two largest fluxes in the annual carbon budget. Yet, these two fluxes compensated each other to a large extent and led to the marsh being a CO 2 sink in 2011 (−78.8±33.6 g C m −2 yr −1 ), near CO 2 -neutral in 2012 (29.7±37.2 g C m −2 yr −1 ), and a CO 2 source in 2013 (92.9±28.0 g C m −2 yr −1 ). The CH 4 emission was consistently high with a three-year average of 50.8±1.0 g C m −2 yr −1 . Considerable hydrologic carbon flowed laterally both into and out of the marsh (108.3±5.4 and 86.2±10.5 g C m −2 yr −1 , respectively). In total, hydrologic carbon fluxes contributed ~23±13 g C m −2 yr −1 to the three-year carbon budget. Our findings highlight the importance of lateral hydrologic inflows/outflows in wetland carbon budgets, especially in those characterized by a flow-through hydrologic regime. In addition, different carbon fluxes responded unequally to climate variability/anomalies and, thus, the total carbon budgets may vary drastically among years. This article is protected by copyright. All rights reserved.
Print ISSN:
1354-1013
Electronic ISSN:
1365-2486
Topics:
Biology
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Energy, Environment Protection, Nuclear Power Engineering
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Geography
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