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Abstract The heterogeneity of carbon dioxide (CO2) and methane (CH4) sources within and across watersheds presents a challenge to understanding the contributions of different ecosystem patch types to stream corridor and watershed carbon cycling. Changing hydrologic connections between corridor patches (e.g., streams, vernal pools, hillslopes) can influence stream corridor greenhouse gas emissions, but the spatiotemporal dynamics of emissions within and among corridor patches are not well‐quantified. To identify patterns and sources of carbon emissions across stream corridors, we measured gas concentrations and fluxes over two summers at Coweeta Hydrologic Laboratory, NC. We sampled CO2and CH4along four stream channels (including flowing and dry reaches), adjacent vernal pools, and riparian hillslopes. Stream CO2and CH4emissions were spatially heterogeneous. All streams were sources of CO2to the atmosphere (median = 97.2 mmol m−2d−1) but were sources or sinks of CH4depending on location (−0.19 to 4.57 mmol m−2d−1). CO2emissions were lower during the drier of two sampling years but were stable from month to month in the drier summer. CO2and CH4emissions also varied by both corridor and patch type; the presence of a vernal pool in the corridor had the strongest impact on emissions. Vernal pool patches emitted more CO2and CH4(246 and 1.95 mmol m−2d−1, respectively) than their adjacent streams. High resolution sampling of carbon fluxes from patches within and among stream corridors improves our understanding of the connections between terrestrial, riparian, and aquatic zones in a watershed and their contributions to overall catchment carbon emissions.
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Spatial and temporal heterogeneity of methane ebullition in lowland headwater streams and the impact on sampling design
Abstract Headwater streams are known sources of methane (CH4) to the atmosphere, but their contribution to global scale budgets remains poorly constrained. While efforts have been made to better understand diffusive fluxes of CH4in streams, much less attention has been paid to ebullitive fluxes. We examine the temporal and spatial heterogeneity of CH4ebullition from four lowland headwater streams in the temperate northeastern United States over a 2‐yr period. Ebullition was observed in all monitored streams with an overall mean rate of 1.00 ± 0.23 mmol CH4m−2d−1, ranging from 0.01 to 1.79 to mmol CH4m−2d−1across streams. At biweekly timescales, rates of ebullition tended to increase with temperature. We observed a high degree of spatial heterogeneity in CH4ebullition within and across streams. Yet, catchment land use was not a simple predictor of this heterogeneity, and instead patches scale variability weakly explained by water depth and sediment organic matter content and quality. Overall, our results support the prevalence of CH4ebullition from streams and high levels of variability characteristic of this process. Our findings also highlight the need for robust temporal and spatial sampling of ebullition in lotic ecosystems to account for this high level of heterogeneity, where multiple sampling locations and times are necessary to accurately represent the mean rate of flux in a stream. The heterogeneity observed likely indicates a complex set of drivers affect CH4ebullition from streams which must be considered when upscaling site measurements to larger spatial scales.
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- Award ID(s):
- 1637630
- PAR ID:
- 10375040
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 66
- Issue:
- 12
- ISSN:
- 0024-3590
- Page Range / eLocation ID:
- p. 4063-4076
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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