Short-interval wildfire and drought overwhelm boreal forest resilience

• Published in: Scientific reports Vol. 9; no. 1; pp. 18796 - 12
• Main Authors: Whitman, Ellen, Parisien, Marc-André, Thompson, Dan K., Flannigan, Mike D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.12.2019; Nature Publishing Group
• Subjects: 631/158/2454; 704/106/694/2739; 704/158/2465; Boreal forests; Climate change; Drought; Droughts; Fires; Forests; Humanities and Social Sciences; multidisciplinary; North America; Plant species; Science; Science (multidisciplinary); Taiga; Time; Vegetation cover; Wildfires; North America
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-55036-7

The size and frequency of large wildfires in western North America have increased in recent years, a trend climate change is likely to exacerbate. Due to fuel limitations, recently burned forests resist burning for upwards of 30 years; however, extreme fire-conducive weather enables reburning at shorter fire-free intervals than expected. This research quantifies the outcomes of short-interval reburns in upland and wetland environments of northwestern Canadian boreal forests and identifies an interactive effect of post-fire drought. Despite adaptations to wildfire amongst boreal plants, post-fire forests at paired short- and long-interval sites were significantly different, with short-interval sites having lower stem densities of trees due to reduced conifer recruitment, a higher proportion of broadleaf trees, less residual organic material, and reduced herbaceous vegetation cover. Drought reinforced changes in proportions of tree species and decreases in tree recruitment, reinforcing non-resilient responses to short-interval reburning. Drier and warmer weather will increase the incidence of short-interval reburning and amplify the ecological changes such events cause, as wildfire activity and post-fire drought increase synergistically. These interacting disturbances will accelerate climate-driven changes in boreal forest structure and composition. Our findings identify processes of ongoing and future change in a climate-sensitive biome.