Abstract
AbstractAltered fire regimes can drive major and enduring compositional shifts or losses of forest ecosystems. In western North America, ponderosa pine and dry mixed‐conifer forest types appear increasingly vulnerable to uncharacteristically extensive, high‐severity wildfire. However, unburned or only lightly impacted forest stands that persist within burn mosaics—termed fire refugia—may serve as tree seed sources and promote landscape recovery. We sampled tree regeneration along gradients of fire refugia proximity and density at 686 sites within the perimeters of 12 large wildfires that occurred between 2000 and 2005 in the interior western United States. We used generalized linear mixed‐effects models to elucidate statistical relationships between tree regeneration and refugia pattern, including a new metric that incorporates patch proximity and proportional abundance. These relationships were then used to develop a spatially explicit landscape simulation model. We found that regeneration by ponderosa pine and obligate‐seeding mixed‐conifer tree species assemblages was strongly and positively predicted by refugia proximity and density. Simulation models revealed that for any given proportion of the landscape occupied by refugia, small patches produced greater landscape recovery than large patches. These results highlight the disproportionate importance of small, isolated islands of surviving trees, which may not be detectable with coarse‐scale satellite imagery. Findings also illustrate the interplay between patch‐scale resistance and landscape‐scale resilience: Disturbance‐resistant settings (fire refugia) can entrain resilience (forest regeneration) across the burn matrix. Implications and applications for land managers and conservation practitioners include strategies for the promotion and maintenance of fire refugia as components of resilient forest landscapes.
Highlights
Changing fire regimes, associated with climate and land use, have the potential to catalyze large-scale transformations of forest ecosystems (Savage and Mast 2005, Serra-Diaz et al 2018)
In western North America, ponderosa pine (Pinus ponderosa) and dry mixed-conifer forest types were highly resistant to low-severity fires with short return intervals prior to European settlement, but this fire regime was impeded over a century ago (Covington and Moore 1994, Allen et al 2002)
At 22/182 refugium sites (12%), no live residual trees occurred within sample units, though these plots fell within forested refugia, reflecting
Summary
Changing fire regimes, associated with climate and land use, have the potential to catalyze large-scale transformations of forest ecosystems (Savage and Mast 2005, Serra-Diaz et al 2018). In western North America, ponderosa pine (Pinus ponderosa) and dry mixed-conifer forest types were highly resistant to low-severity fires with short return intervals prior to European settlement, but this fire regime was impeded over a century ago (Covington and Moore 1994, Allen et al 2002). Resultant fuel accumulations, interacting with climate drivers, have led to fires with uncharacteristically large high-severity patches in these systems (Fornwalt et al 2016), which can initiate shifts toward non-forested states (Savage and Mast 2005, Airey Lauvaux et al 2016, Chambers et al 2016, Coop et al 2016, Barton and Poulos 2018, Haffey et al 2018)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
