Future transitions from a conifer to a deciduous-dominated landscape are accelerated by greater wildfire activity and climate change in interior Alaska

Weiss, Shelby A.; Marshall, Adrienne M.; Hayes, Katherine; Nicolsky, Dmitry; Buma, Brian; Lucash, Melissa S.

doi:10.1007/s10980-023-01733-8

Cited by 2 publications

(1 citation statement)

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“…Shortening fire‐free intervals are a key mechanism by which the historic carbon sink of boreal forests will become a net source, with younger forests having less time to store carbon in live biomass and organic soils before reburning (Dieleman et al., 2020; Stinson et al., 2011). Climate change‐driven increases in short‐interval reburning are likely to lead to ecosystem reorganization through direct and indirect effects on vegetation assemblies (Sharma et al., 2022; Stralberg et al., 2018; Weiss et al., 2023). In any disturbance‐prone system, a substantial weakening of the negative feedback between disturbance and its bottom‐up environmental constraints will invariably lead to ecological consequences (Tepley et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

A modest increase in fire weather overcomes resistance to fire spread in recently burned boreal forests

Whitman,

Barber,

Jain

et al. 2024

Global Change Biology

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Recently burned boreal forests have lower aboveground fuel loads, generating a negative feedback to subsequent wildfires. Despite this feedback, short‐interval reburns (≤20 years between fires) are possible under extreme weather conditions. Reburns have consequences for ecosystem recovery, leading to enduring vegetation change. In this study, we characterize the strength of the fire‐fuel feedback in recently burned Canadian boreal forests and the weather conditions that overwhelm resistance to fire spread in recently burned areas. We used a dataset of daily fire spread for thousands of large boreal fires, interpolated from remotely sensed thermal anomalies to which we associated local weather from ERA5‐Land for each day of a fire's duration. We classified days with >3 ha of fire growth as spread days and defined burned pixels overlapping a fire perimeter ≤20 years old as short‐interval reburns. Results of a logistic regression showed that the odds of fire spread in recently burned areas were ~50% lower than in long‐interval fires; however, all Canadian boreal ecozones experienced short‐interval reburning (1981–2021), with over 100,000 ha reburning annually. As fire weather conditions intensify, the resistance to fire spread declines, allowing fire to spread in recently burned areas. The weather associated with short‐interval fire spread days was more extreme than the conditions during long‐interval spread, but overall differences were modest (e.g. relative humidity 2.6% lower). The frequency of fire weather conducive to short‐interval fire spread has significantly increased in the western boreal forest due to climate warming and drying (1981–2021). Our results suggest an ongoing degradation of fire‐fuel feedbacks, which is likely to continue with climatic warming and drying.

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