Top-down control of methane emission and nitrogen cycling by waterfowl.
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Aquatic herbivores impose top-down control on the structure of wetland ecosystems, but the biogeochemical consequences of herbivory on methane (CH4 ) and nitrogen (N) are poorly known. To investigate the top-down effects of waterfowl on wetland biogeochemistry, we implemented exclosure experiments in a major waterfowl overwintering wetland in the southeastern United States over two growing seasons. We found that herbivory inhibited the oxidation of CH4 , leading to a mean increase in emission by 230% over control plots, and prevented nitrification, as indicated by low nitrate availability and undetectable emissions of nitrous oxide. Herbivory reduced belowground biomass of macrophytes, retarding the subsequent spring emergence of aerenchymous stems, effectively starving wetland soils of oxygen necessary for CH4 oxidation and nitrification. The recognition that important populations of aquatic herbivores may influence the capacity for wetlands to emit greenhouse gases and cycle N is particularly salient in the context of climate change and nutrient pollution mitigation goals. For example, our results suggest that (1) annual emissions of 23 Gg CH4 /yr from ~57 000 ha of publicly owned waterfowl impoundments in the southeastern United States could be tripled by overgrazing and that (2) waterfowl impoundments may export as much N as agricultural fields. We discuss potential implications for habitat management in the context of historic wetland loss and waterfowl population recovery.
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Winton, R Scott, and Curtis J Richardson (2017). Top-down control of methane emission and nitrogen cycling by waterfowl. Ecology, 98(1). pp. 265–277. 10.1002/ecy.1640 Retrieved from https://hdl.handle.net/10161/15699.
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Curtis J. Richardson
Curtis J. Richardson is Professor of Resource Ecology and founding Director of the Duke University Wetland Center in the Nicholas School of the Environment. Dr. Richardson earned his degrees from the State University of New York and the University of Tennessee.
His research interests in applied ecology focus on long-term ecosystem response to large-scale perturbations such as climate change, toxic materials, trace metals, flooding, or nutrient additions. He has specific interests in phosphorus nutrient dynamics in wetlands and the effects of environmental stress on plant communities and ecosystem functions and services. The objectives of his research are to utilize ecological principles to develop new approaches to environmental problem solving. The goal of his research is to provide predictive models and approaches to aid in the management of ecosystems. Recent research activities: 1) wetland restoration of plant communities and its effects on regional water quality and nutrient biogeochemical cycles, 2) the development of ecosystem metrics as indices of wetland restoration success, 3) the effects of nanomaterial on wetland and stream ecosystem processes, 4) the development of ecological thresholds along environmental gradients, 5) wetland development trends and restoration in coastal southeastern United States, 6) the development of an outdoor wetland and stream research and teaching laboratory on Duke Forest, 7) differential nutrient limitation (DNL) as a mechanism to overcome N or P limitations across trophic levels in wetland ecosystems, and 8) carbon sequestration in coastal North Carolina pocosins.Richardson oversees the main analytical lab in NSOE, which is open to students and faculty. Dr. Richardson has been listed in Who's Who in Science™ annually since 1989 and was elected President of the Society of Wetland Scientists in 1987-88. He has served on many editorial review committees for peer-reviewed scientific journals, and he is a past Chair of the Nicholas School Division of Environmental Sciences and Policy. Dr. Richardson is a Fellow of the American Association for the Advancement of Science, the Society of Wetland Scientists, and the Soil Science Society of America.
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