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Research article - Peer-reviewed, 2021

The impact of wildfire on biogeochemical fluxes and water quality in boreal catchments

Granath, Gustaf; Evans, Christopher D.; Strengbom, Joachim; Folster, Jens; Grelle, Achim; Stromqvist, Johan; Kohler, Stephan J.

Abstract

Wildfires are the major disturbance in boreal ecosystems and are of great importance for the biogeochemical cycles of carbon (C) and nutrients. However, these fire-induced impacts are hard to quantify and are rarely assessed together at an ecosystem level incorporating both aquatic and terrestrial environments. Following a wildfire in Sweden in an area with ongoing monitoring, we conducted a pre-fire (9 years) and post-fire (4 years) multi-catchment investigation of element losses (combustion and leaching) and impacts on water quality. Direct C and nitrogen (N) losses through combustion were ca. 4500 and 100 gm(-2), respectively. Net CO2 loss associated with soil and biomass respiration was similar to 150 g C m(-2) during the first year, but the ecosystem started to show net CO2 uptake in June 3 years post-fire. Aquatic C and N losses the first 12 months post-fire were 7 and 0.6 gm(-2), respectively. Hence, soil respiration comprised a non-negligible part of the post-fire C loss, whereas aquatic C losses were minor and did not increase post-fire. However, other elements (e.g. Ca, S) exhibited ecologically relevant increases in fluvial export and concentration with large peaks in the immediate post-fire period. The temporal dynamics of stream concentrations (Ca2+, Mg2+, K+,SO4-2, Cl-, NH4+, total organic N) suggest the presence of faster- and slower-release nutrient pools with half-lives of around 2 weeks and 4 months which we attribute to physicochemically and biologically mediated mobilization processes, respectively. Three years after the fire, it appears that dissolved fluxes of nutrients have largely returned to pre-fire conditions, but there is still net release of CO2.

Published in

Biogeosciences
2021, volume: 18, number: 10, pages: 3243-3261
Publisher: COPERNICUS GESELLSCHAFT MBH

Authors' information

Granath, Gustaf
Uppsala University
UK Centre for Ecology and Hydrology (UKCEH)
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Swedish University of Agricultural Sciences, Department of Ecology
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Swedish University of Agricultural Sciences, Department of Ecology
Stromqvist, Johan
Swedish Meteorological and Hydrological Institute
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment

Sustainable Development Goals

SDG6 Clean water

UKÄ Subject classification

Ecology
Soil Science

Publication Identifiers

DOI: https://doi.org/10.5194/bg-18-3243-2021

URI (permanent link to this page)

https://res.slu.se/id/publ/112610