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Abstract Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO2) and methane (CH4) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO2and CH4. Here, we measured partial pressures of CO2(pCO2) and CH4(pCH4) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability ofpCO2andpCH4in space and time. Summer means ofpCO2andpCH4were inversely related to waterbody size and positively related to floating vegetative cover;pCO2was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonalpCO2by up to 26%, mean seasonalpCH4could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability inpCH4and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities.
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CO2 and CH4 Concentrations in Headwater Wetlands Influenced by Morphology and Changing Hydro-Biogeochemical Conditions
Abstract Headwater wetlands are important sites for carbon storage and emissions. While local- and landscape-scale factors are known to influence wetland carbon biogeochemistry, the spatial and temporal heterogeneity of these factors limits our predictive understanding of wetland carbon dynamics. To address this issue, we examined relationships between carbon dioxide (CO2) and methane (CH4) concentrations with wetland hydrogeomorphology, water level, and biogeochemical conditions. We sampled water chemistry and dissolved gases (CO2and CH4) and monitored continuous water level at 20 wetlands and co-located upland wells in the Delmarva Peninsula, Maryland, every 1–3 months for 2 years. We also obtained wetland hydrogeomorphologic metrics at maximum inundation (area, perimeter, and volume). Wetlands in our study were supersaturated with CO2(mean = 315 μM) and CH4(mean = 15 μM), highlighting their potential role as carbon sources to the atmosphere. Spatial and temporal variability in CO2and CH4concentrations was high, particularly for CH4, and both gases were more spatially variable than temporally. We found that groundwater is a potential source of CO2in wetlands and CO2decreases with increased water level. In contrast, CH4concentrations appear to be related to substrate and nutrient availability and to drying patterns over a longer temporal scale. At the landscape scale, wetlands with higher perimeter:area ratios and wetlands with higher height above the nearest drainage had higher CO2and CH4concentrations. Understanding the variability of CO2and CH4in wetlands, and how these might change with changing environmental conditions and across different wetland types, is critical to understanding the current and future role of wetlands in the global carbon cycle.
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- Award ID(s):
- 1856200
- PAR ID:
- 10546008
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Ecosystems
- Volume:
- 27
- Issue:
- 7
- ISSN:
- 1432-9840
- Format(s):
- Medium: X Size: p. 999-1019
- Size(s):
- p. 999-1019
- Sponsoring Org:
- National Science Foundation
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