Controls on methane concentrations and fluxes in streams draining human-dominated landscapes

TitleControls on methane concentrations and fluxes in streams draining human-dominated landscapes
Publication TypeJournal Article
Year of Publication2016
AuthorsCrawford, J. T., and Stanley E. H.
JournalEcological Applications
Volume26
Issue5
Number of Pages1581-1591
Date PublishedJul
Type of ArticleArticle
Reprint Number1051-0761
LTER Accession NumberWOS:000379603900021
Keywordsagriculture; urbanization; sediments; nutrients; methane; climate, fine sediment; inland waters, rice field soil; carbon-dioxide; headwater stream; nutrient retention;, terrestrial carbon; interior alaska; nitrogen-cycle; hyporheic zone;
Abstract

Streams and rivers are active processors of carbon, leading to significant emissions of CO2 and possibly CH4 to the atmosphere. Patterns and controls of CH4 in fluvial ecosystems remain relatively poorly understood. Furthermore, little is known regarding how major human impacts to fluvial ecosystems may be transforming their role as CH4 producers and emitters. Here, we examine the consequences of two distinct ecosystem changes as a result of human land use: increased nutrient loading (primarily as nitrate), and increased sediment loading and deposition of fine particles in the benthic zone. We did not find support for the hypothesis that enhanced nitrate loading down-regulates methane production via thermodynamic or toxic effects. We did find strong evidence that increased sedimentation and enhanced organic matter content of the benthos lead to greater methane production (diffusive + ebullitive flux) relative to pristine fluvial systems in northern Wisconsin (upper Midwest, USA). Overall, streams in a human-dominated landscape of southern Wisconsin were major regional sources of CH4 to the atmosphere, equivalent to similar to 20% of dairy cattle emissions, or similar to 50% of a landfill's annual emissions. We suggest that restoration of the benthic environment (reduced fine deposits) could lead to reduced CH4 emissions, while decreasing nutrient loading is likely to have limited impacts to this ecosystem process.

DOI10.1890/15-1330
Print Copy LocationEcol. Appl.