Impacts of fire on non-native plant recruitment in black spruce forests of interior Alaska

Abstract

Climate change is expected to increase the extent and severity of wildfires throughout the boreal forest. Historically, black spruce (Picea mariana (Mill.) B.S.P.) forests in interior Alaska have been relatively free of non-native species, but the compounding effects of climate change and an altered fire regime could facilitate the expansion of non-native plants. We tested the effects of wildfire on non-native plant colonization by conducting a seeding experiment of non-native plants on different substrate types in a burned black spruce forest, and surveying for non-native plants in recently burned and mature black spruce forests. We found few non-native plants in burned or mature forests, despite their high roadside presence, although invasion of some burned sites by dandelion (Taraxacum officinale) indicated the potential for non-native plants to move into burned forest. Experimental germination rates were significantly higher on mineral soil compared to organic soil, indicating that severe fires that combust much of the organic layer could increase the potential for non-native plant colonization. We conclude that fire disturbances that remove the organic layer could facilitate the invasion of non-native plants providing there is a viable seed source and dispersal vector.

Does fire always accelerate shrub expansion in Arctic tundra? Examining a novel grass-dominated successional trajectory on the Seward Peninsula

“…In boreal forest systems, successional trajectory is strongly linked to burn severity (Johnstone, Hollingsworth, and Chapin 2008;Hollingsworth et al 2013), where lowseverity fires promote relay succession and a quick return to pre-fire vegetation and soil conditions, whereas highseverity fires can trigger a shift in successional trajectory and the recruitment of novel species, both native (Johnstone et al 2010) and invasive (X. J. Walker et al 2017). The effect of burn severity on vegetation and recruitment in Alaska tundra is documented but limited (Bret-Harte et al 2013;Hewitt et al 2016).…”

“…In high-latitude systems, a large body of research focuses on climate-induced changes in the fire regime of the boreal forest (e.g., Bergeron and Flannigan 1995;Soja et al 2006;Chapin et al 2010). In arctic tundra, however, wildfire has been less frequent or has occurred in remote localities where small short-lived fires or their fire scars were not observed and are therefore not part of the historical record (D. A. Walker and Walker 1991). The warming the Arctic has experienced over the last fifty years (Hinzman et al 2005) is significant and coincident with an increase in the frequency and severity of wildfire (French et al 2015;Masrur, Pretrov, and De Groote 2018).…”