Wallin, Marcus
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Abstract
Boreal streams represent potentially important conduits for the exchange of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere. The gas transfer coefficient of CO2 (K-CO2) is a key variable in estimating this source strength, but the scarcity of measured values in lotic systems creates a risk of incorrect flux estimates even when stream gas concentrations are well known. This study used 114 independent measurements of K-CO2 from 14 stream reaches in a boreal headwater system to determine and predict spatiotemporal variability in K-CO2. The K-CO2 values ranged from 0.001 to 0.207 min(-1) across the 14 sites. Median K-CO2 for a specific site was positively correlated with the slope of the stream reach, with higher gas transfer coefficients occurring in steeper stream sections. Combining slope with a width/depth index of the stream reach explained 83% of the spatial variability in K-CO2. Temporal variability was more difficult to predict and was strongly site specific. Variation in K-CO2, rather than pCO(2), was the main determinant of stream CO2 evasion. Applying published generalized gas transfer velocities produced an error of up to 100% in median instantaneous evasion rates compared to the use of actual measured K-CO2 values from our field study. Using the significant relationship to local slope, the median K-CO2 was predicted for 300,000 km of watercourses (ranging in stream order 1-4) in the forested landscape of boreal/nemoral Sweden. The range in modeled stream order specific median K-CO2 was 0.017-0.028 min(-1) and there was a clear gradient of increasing K-CO2 with lower stream order. We conclude that accurate regional scale estimates of CO2 evasion fluxes from running waters are possible, but require a good understanding of gas exchange at the water surface.
Published in
Global Biogeochemical Cycles
2011, volume: 25, number: 3, article number: GB3025
Publisher: AMER GEOPHYSICAL UNION
SLU Authors
Öquist, Mats
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
Buffam, Ishi
- University of Wisconsin-Madison
Nisell, Jakob
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Bishop, Kevin
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
UKÄ Subject classification
Meteorology and Atmospheric Sciences
Publication identifier
- DOI: https://doi.org/10.1029/2010GB003975
Permanent link to this page (URI)
https://res.slu.se/id/publ/46256