Topography, Climate and Fire History Regulate Wildfire Activity in the Alaskan Tundra

Abstract

Although the link between climate change and tundra fire activity is well‐studied, we lack an understanding of how fire, vegetation, and topography interact to either amplify or dampen climatic effects on these tundra fires at Pan‐Arctic scale. This study investigated the relative influence of fire history, climate, topography and vegetation on fire occurrence and size in Alaskan tundra (1981–2019) and the potential for self‐reinforcing/limiting fire behavior. Regime shift analysis identified a step increase in fire frequency after 2010 with increased average annual area burned (+96%) and area reburned (+61%) over the 2010–2019 period, consistent with climatic thresholds in fire activity being crossed. Correlation analysis shows variation in fire frequency was positively and significantly related to mean summer temperatures. The competing roles of fire history and bio‐climate were investigated via random forest models using (a) environmental conditions and (b) environmental conditions and fire history. Fire occurrence was primarily driven by topographic complexity and elevation, suggesting that areas at 50–200 m elevation with gently rolling terrain such as the Arctic Foothills of the Brooks Range or the Kotzebue Lowlands in northern Alaska will likely become hotspots of fire activity. In contrast, fire size was affected mainly by fire history and winter‐spring climate, which demonstrates the importance of both fuel limitations and self‐reinforcing (e.g., rapid fuel regrowth following smaller‐sized fires) fire‐vegetation interactions in regulating tundra fire activity. Future modeling studies need more nuanced representations of fire‐terrain and fire‐vegetation interactions to accurately project how tundra ecosystems may respond to climatic warming.

Global Warming Reshapes European Pyroregions

“…Indeed, a warming climate may temper increases in fire activity by decreasing fuel availability in dry regions through aridification (Mauri et al., 2022; Pausas & Paula, 2012). Conversely, this may boost fire activity in other regions through transitions from forested systems to more flammable vegetation types (i.e., shrublands), or through increasing dead fuel from drought‐induced forest diebacks (Liang et al., 2017; Masrur et al., 2022). Additionally, an increase in fuel accumulation due to systematic fire suppression (Moreira et al., 2020; Parisien et al., 2020) could exacerbate the signal of climate change on fire activity, particularly high‐intensity fires.…”

Tundra fire increases the likelihood of methane hotspot formation in the Yukon–Kuskokwim Delta, Alaska, USA

“…The ABoVE airborne campaigns have collected airborne hyperspectral imagery over other tundra fire burn perimeters: near Kougarok on the Seward Peninsula (Liljedahl et al 2007, Iwahana et al 2016, in the Noatak River Valley (Loboda et al 2013, French et al 2015, He et al 2021, Masrur et al 2022, over the Anaktuvuk River burn scar, (Rocha and Shaver 2011a, 2011bJones et al 2009, 2015 and the 2022 Contact Creek fire near King Salmon, AK. We plan to extend the CH 4 hotspot analyses to these disturbances.…”

Summer drought weakens land surface cooling of tundra vegetation

“…Despite newly emerging and trends toward more extreme events in the Arctic region, our understanding of the change in drought occurrence is still uncertain (Meredith et al 2019, Walsh et al 2020. Identifying responses and feedbacks of tundra ecosystems to heatwaves and droughts is relevant, as such extreme events often precede intense wildfire seasons like in Siberia in 2020 (Loranty et al 2016, Masrur et al 2022, Talucci et al 2022. The question remains how land surface cooling develops within growing seasons and whether the temporal snapshots presented here hold true for other moisture regimes and atmospheric conditions.…”