Canadian Forest Service Publications
Groundwater inflows control patterns and sources of greenhouse gas emissions from streams. 2019. Lupon, A.; Denfield, B.A.; Laudon, H.; Leach, J.; Karlsson, J.; Sponseller, R.A. Limnology and Oceanography: 10.1002/lno.11134.
Issued by: Great Lakes Forestry Centre
Catalog ID: 39778
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Plain Language Summary
Headwater streams emit substantial amounts of carbon dioxide (CO2) and methane (CH4) into the atmosphere. However, the influence of groundwater-stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections through a detailed study of a 1.4 km boreal stream that drains a lake and is hydrologically fed by multiple groundwater input zones. We measured stream and groundwater dissolved organic C, CO2, and CH4 concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. CH4 and CO2 concentrations peaked at the lake outlet and after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. In-stream mineralization of terrestrial dissolved organic C and CH4 inputs accounted for 17‒51% of stream CO2 emissions and this contribution was the greatest during relatively high flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream carbon concentrations, transformations, and emissions by acting as a direct source of gases and by suppling organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater-stream connections are crucial for mechanistically understanding and scaling carbon evasion rates from headwaters.