Impacts of clear-cutting on groundwater discharge rates into a boreal stream

Abstract

Clear-cutting is one of the major disturbances impacting forest carbon (C) storage by increasing dissolved C in soils that can be easily transported through groundwater and processed in recipient waters such as lakes and streams. Forest clear-cutting has been found to increase concentrations of greenhouse gases (GHGs) (carbon dioxide (CO2) and methane (CH4)) in first-order boreal streams. However, the importance of groundwater inflows in controlling stream GHG budgets is still uncertain. Here we combined a catchment experiment and the use of natural tracers (i.e., radon (222Rn)) to quantify the impact of forest clear-cuts and buffer zones on groundwater inflow rates into streams. Analyses of 222Rn concentrations in stream and groundwater, collected between April and October before and after clear-cut (2020 and 2021, respectively), showed that clear-cut increased groundwater discharge rates to the stream, resulting in higher inputs of dissolved C which likely increase GHG emissions to the atmosphere. Uncertainties in the results associated with the method’s limitations are also discussed