Abstract
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 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+ ,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.
Highlights
Wildfires are the major disturbance agent in boreal ecosystems and are expected to increase in size and frequency (Flannigan et al, 2009)
Wildfires influence the biogeochemical cycles of nitrogen (N) and major cations (Brais et al, 2000; Grier, 1975; Smithwick et al, 2005), which can influence post-fire ecosystem productivity, an issue which has been discussed for decades (e.g. Ahlgren and Ahlgren, 1960; Grier, 1975)
In forest soils and ground vegetation, most of the C and N losses were from the O horizon, while the contribution of the shrub vegetation was negligible
Summary
Wildfires are the major disturbance agent in boreal ecosystems and are expected to increase in size and frequency (Flannigan et al, 2009). Wildfires influence the biogeochemical cycles of nitrogen (N) and major cations (Brais et al, 2000; Grier, 1975; Smithwick et al, 2005), which can influence post-fire ecosystem productivity, an issue which has been discussed for decades Ahlgren and Ahlgren, 1960; Grier, 1975) Losses occur both as emissions during the fire and through post-fire losses via runoff. These fireinduced impacts are hard to quantify and are rarely assessed at an ecosystem level including both aquatic and terrestrial environments (Amiro et al, 2010; Brais et al, 2000; Rhoades et al, 2019; Turner et al, 2007). We present a unique pre- and post-fire multi-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
