Regional variation in the direction and strength of fire–vegetation feedbacks under contemporary fire regimes

Authors: Alan Tepley*, Canadian Forest Service, Northern Forestry Centre, Jonathan R Thompson, Harvard Forest, Kristina J Anderson-Teixeira, Smithsonian Conservation Biology Institute, Smithsonian Tropical Research Institute, Josep M Serra-Diaz, AgroParisTech – Paris Institute of Technology for Life, Food and Environmental Sciences, Xianli Wang, Canadian Forest Service, Northern Forestry Centre, Marc-André Parisien, Canadian Forest Service, Northern Forestry Centre
Topics: Biogeography, Global Change
Keywords: wildfire, climate change, feedbacks, null model, reburn
Session Type: Virtual Paper
Day: 4/7/2021
Start / End Time: 9:35 AM / 10:50 AM
Room: Virtual 9
Presentation File: No File Uploaded

Climate change is increasing wildfire activity while creating harsher conditions for trees to regenerate after fire. These changes place certain forest regions at increasing risk of conversion to persistent non-forest cover. Vulnerability to such conversion depends, in part, on how fire-driven changes to vegetation alter the occurrence and effects of subsequent fire (i.e., fire–vegetation feedbacks), which could potentially either exacerbate or buffer against climate change-driven increases in wildfire activity. Here, we compare the direction and strength of fire–vegetation feedbacks across three forest regions: the Klamath Mountains of northern California and southwestern Oregon, subalpine forests of the US Northern Rockies, and Canadian boreal forests. We evaluate how the extent of short-interval fires (reburns) and repeated high-severity fire differs from that expected under region-specific null models with no fire–vegetation feedbacks.

Since 1984, reburns in the Klamath Mountains were 96,000 ha more extensive, and high-severity reburns represented 5,000 ha more area than expected under the null model. In Northern Rockies subalpine forests, by contrast, reburns and high-severity reburns accounted for 85,000 ha and 7,000 ha less area, respectively, than expected under the null model. Reburns were also less extensive than expected throughout boreal Canada, where the departure from the null model was strongest in the most fire-prone regions. The propensity for reburns, and particularly high-severity reburns, in the Klamath Mountains places this region at risk of conversion from forest to persistent non-forest cover. Resistance to reburning in subalpine and boreal forests could limit the potential for fire-driven forest conversion.

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