Integrating Ecosystem Patch Contributions to Stream Corridor Carbon Dioxide and Methane Fluxes

• Published in: Journal of geophysical research. Biogeosciences 2021-09, Vol.126 (9), p.n/a
• Main Authors: Bretz, Kristen A., Jackson, Alexis R., Rahman, Sumaiya, Monroe, Jonathon M., Hotchkiss, Erin R.
• Format: Article
• Language: English
• Subjects: Aquatic ecosystems; Atmosphere; Carbon cycle; Carbon dioxide; Carbon dioxide emissions; carbon flux; Carbon sources; Catchment area; Channels; Corridors; Emission measurements; Emissions; Fluxes; Fresh water; Freshwater; Freshwater ecosystems; Gases; Greenhouse effect; Greenhouse gases; Heterogeneity; Hydrology; Inland water environment; Methane; Patches (structures); Pools; Rivers; Sampling; Streams; Summer; Temporary ponds; vernal pools; Watersheds
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2021JG006313

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 CO2 and CH4 along four stream channels (including flowing and dry reaches), adjacent vernal pools, and riparian hillslopes. Stream CO2 and CH4 emissions were spatially heterogeneous. All streams were sources of CO2 to the atmosphere (median = 97.2 mmol m−2d−1) but were sources or sinks of CH4 depending on location (−0.19 to 4.57 mmol m−2d−1). CO2 emissions were lower during the drier of two sampling years but were stable from month to month in the drier summer. CO2 and CH4 emissions 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 CO2 and 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. Plain Language Summary Freshwater ecosystems can be sizable sources of greenhouse gases to the atmosphere. Carbon dioxide and methane emissions from freshwaters can be very different depending on where they are measured in a watershed. As distinct areas near a stream become connected by water moving through the watershed, stream greenhouse gas emissions may change in response to new carbon inputs from these connections. We studied carbon emissions from four streams and their surrounding patches: temporary pools, hillslopes adjacent to streams, and dry beds in stream channels (when water flowed underground). All streams emitted carbon dioxide and some streams were sources of methane to the atmosphere during our summer measurements, but emission magnitudes for both gases varied within each patch. Temporary pools w