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Fire–vegetation feedbacks alter landscape vulnerability to persistent forest loss in response to increasing wildfire activity

Authors: Alan Tepley*, Canadian Forest Service, Jonathan R Thompson, Harvard Forest, Luca Morreale, Boston University, Josep Serra-Diaz, Aarhus University (AU - Denmark), Kristina J Anderson-Teixeira, Smithsonian Conservation Biology Institute, Smithsonian Tropical Research Institute
Topics: Global Change, Biogeography, Hazards and Vulnerability
Keywords: wildfire, climate change, feedbacks, null model, reburn,
Session Type: Paper
Presentation File: No File Uploaded

Climate change is increasing wildfire activity while creating harsher conditions for trees to regenerate after fire. These changes could place certain forest regions at increasing risk of conversion to persistent non-forest cover. Vulnerability to such transformation depends, in part, on the mechanisms by which fire-driven changes to vegetation alter fire recurrence and effects (i.e., fire–vegetation feedbacks), potentially either buffering against or exacerbating climate change-driven increases in wildfire activity.

Here, we compare fire–vegetation feedbacks between mixed-conifer/mixed-evergreen forests of the Klamath Mountains and subalpine forests of the US Northern Rockies. 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.

Reburns in the Klamath Mountains accounted for 6% more area annually (93,360 ha more reburn area since 1984) than expected under a null model with no feedbacks. High-severity reburns were also 1.3 times more extensive than expected under the null model. In Northern Rockies subalpine forests, the mean annual reburn area was 3% less than expected, leading to 75,990 ha less reburn area than expected since 1984. The propensity for reburns, particularly high-severity reburns, in the Klamath Mountains places the region at relatively high risk of conversion from forest to persistent non-forest cover, whereas resistance to reburning in Northern Rockies subalpine forests could limit potential forest conversion. This modeling approach developed here can be easily replicated to compare the vulnerability of other forest regions to vegetation-type-conversion in the face of climate change and altered fire regimes.

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