Spatio-temporal patterns of stream methane and carbon dioxide emissions in a hemiboreal catchment in Southwest Sweden.

ABSTRACT: Global stream and river greenhouse gas emissions seem to be as large as the oceanic C uptake. However, stream and river emissions are uncertain until both spatial and temporal variability have been quantified. Here we investigated in detail the stream CH₄ and CO₂ emissions within a hemiboreal catchment in Southwest Sweden primarily covered by coniferous forest. Gas transfer velocities (k₆₀₀), CH₄ and CO₂ concentrations were measured with multiple methods. Our data supported modelling approaches accounting for various stream slopes, water velocities and discharge. The results revealed large but partially predictable spatio-temporal variabilities in k₆₀₀, dissolved gas concentrations, and emissions. The variability in CO₂ emission was best explained by the variability in k, while dissolved CH₄ concentrations explained most of the variability in CH₄ emission, having implications for future measurements. There were disproportionately large emissions from high slope stream reaches including waterfalls, and from high discharge events. In the catchment, stream reaches with low slope and time periods of moderate discharge dominated (90% of area and 69% of time). Measurements in these stream areas and time periods only accounted for <36% of the total estimated emissions. Hence, not accounting for local or episodic high emissions can lead to substantially underestimated emissions.

SUBMITTER: Natchimuthu S 

PROVIDER: S-EPMC5206626 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature