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Patterns in stream greenhouse gas dynamics from mountains to plains in northcentral Wyoming
Author(s) -
Kuhn C.,
Bettigole C.,
Glick H. B.,
Seegmiller L.,
Oliver C. D.,
Raymond P.
Publication year - 2017
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2017jg003906
Subject(s) - environmental science , greenhouse gas , snowmelt , hydrology (agriculture) , watershed , methane , carbon cycle , carbon dioxide , drainage basin , ecoregion , atmospheric sciences , physical geography , ecology , surface runoff , geology , geography , ecosystem , oceanography , geotechnical engineering , cartography , machine learning , computer science , biology
Quantification of small stream contributions to global carbon cycling is key to understanding how freshwater systems transmit and transform carbon between terrestrial and atmospheric pools. To date, greenhouse gas emissions of carbon dioxide and methane from freshwaters, particularly in mountainous regions, remain poorly characterized due to a lack of direct field observations. Using a unique longitudinal approach, we conducted field surveys across two ecoregions (Middle Rockies and Great Plains) in the Clear Creek watershed, a subwatershed of Wyoming's Powder River Basin. We took direct measurements of stream gases using headspace sampling at 30 sites (8 June to 23 October). We observed the lowest and most variable concentrations in headwaters, which flow through a federally designated alpine wilderness area. By contrast, the Great Plains exhibited 1.45 and 4 times higher p CO 2 and p CH 4 concentrations and the relative contributions of methane increased downstream. Fluxes during snowmelt were 45% and 58% higher for CO 2 and CH 4 than during base flow but overall were lower than estimates for other systems. Variability for p CO 2 was highest during late summer and in the uppermost sections of the headwaters. The high heterogeneity and common undersaturation observed through space and time, especially in the mountains, suggest that downscaled regional estimates may fail to capture variability in fluxes observed at these smaller scales. Based on these results, we strongly recommend higher resolution time series studies and increased scrutiny of systems at near equilibrium, inclusive of winter storage and ice‐off events, to improve our understanding of the effects of seasonal dynamics on these processes.