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

Granath, Gustaf; Evans, Christopher D. ORCID: https://orcid.org/0000-0002-7052-354X; Strengbom, Joachim; Fölster, Jens; Grelle, Achim; Strömqvist, Johan; Köhler, Stephan J.. 2021 The impact of wildfire on biogeochemical fluxes and water quality in boreal catchments. Biogeosciences, 18 (10). 3243-3261. 10.5194/bg-18-3243-2021

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Abstract/Summary

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 g m−2, respectively. Net CO2 loss associated with soil and biomass respiration was ∼ 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 g m−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+ ,SO−24, Cl− ,NH+4, 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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/bg-18-3243-2021
UKCEH and CEH Sections/Science Areas:	Soils and Land Use (Science Area 2017-)
ISSN:	1726-4170
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Ecology and Environment
Date made live:	08 Jul 2021 12:05 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/530642

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