Wildfire-induced soil erosion in northern Finland watersheds

Climate change is expected to increase the frequency and severity of wildfires in boreal forests, raising concerns about ecosystem resilience. We investigated the correspondence between fire events and soil erosion events in northern Finland during the Holocene (last 11,000 years). We analysed charcoal particles to reconstruct the local fire histories of two boreal lake catchments. Then, using magnetic susceptibility analysis, we identified sedimentary inputs into the lakes due to soil erosion events. Sediment geochemistry analysis revealed that high-severity fires corresponding with soil erosion events not only affect the organic soil horizons, but also the topmost mineral horizons by leaching aluminium, calcium, nitrogen, silicon and heavy metals into aquatic ecosystems. Because the effects of high-severity fires on soil properties are long-lasting, increased fire severity under climate change in northern Finland could hamper forest resilience in addition to contaminating aquatic ecosystems.