What are fire refugia?

Fire refugia are locations on the landscape burned less severely and/or less frequently than surrounding areas. The taxonomy of fire refugia included attributes based on severity of burning (unburned to lower severity), predictability of occurrence (predictable to stochastic patterns), spatial scale of the pattern (from individual plant to stands, landscapes, and regions), and persistence (one fire event to multiple fire events). All of these features of fire refugia are important and can have different ecological implications. One way to avoid confusion in talking about fire refugia is to use the phrasing “from what for what”, similar to best practices in using the term resilience. Our work here focuses on identifying predictable refugia from high-severity fire for existing and potential mature and old-growth forests. It is important to recognize that local refugial patch conditions support their persistence, as well as the spatial context in the landscape that affects fire flow to the forest patch.

Concepts and models of fire refugia are increasingly a part of forest management discussions in the context of wildland fire and global change. Recognizing that fire refugia terminology can be used for locations that burn at lower severity when the surrounding area experiences higher severity fire, as well as locations that are truly unburned, is important for the application of fire refugia science. Lower severity fire, or underburning, dominated by surface fire may be a critical ingredient for maintaining fire refugia across a broad geography of forest types. This is certainly true for historically frequent-fire ecosystems, where chronic low-severity fire anchored the dry forest system as a refugium from large patches of high-severity fire and maintained open canopy, old forest characteristics across large areas. With fire exclusion in fire-prone landscapes, later-successional forest conditions have developed, but these stands are not in the right place (terrain position) to provide microclimate and vegetation structure conducive to fire refugia through most fire events. These “apparent” closed canopy fire refugia may be vulnerable to stand-replacing fire, insects, and pathogens/disease and should be prioritized for restoration and adaptation silvicultural treatments in drier forest types or where open forest conditions are a desired objective, and some moist forest. Additionally, in the moist to wet Douglas-fir region on the west slopes of the Cascade Mountains, recent research highlights the widespread role of non-stand-replacing fire in the structural development of some old forests and this emerging understanding will be important to integrate into fire refugia science, forest conservation, and adaption to climate change.

Locations that remain unburned throughout their successional sequence are a classic example of fire refugia. The fire refugia concept originally presented by Camp et al. (1997) focused on locations with no evidence of fire that developed closed canopy, late-successional forest in pre-colonization conditions of the Swauk Late-Successional Reserve (LSR) in the Okanogan-Wenatchee National Forest. Camp et al. (1997) recognized the historically frequent fire context of their work and were specifically looking for locations where fire flow was interrupted by biophysical including topoedaphic conditions of the stand. Overall, the tree structure and microclimate within many older, closed canopy Douglas-fir dominated forests appear to moderate fire behavior, particularly in core areas of old-growth away from forest edge. Accordingly, identifying the geography of mature and old-growth forests that are more likely to persist into the future as fire refugia with a hands-off approach based on their inherent fire-resistant “asbestos forest” qualities, versus those that would benefit from vegetation management or underburning within or around them to make them more durable and restoring their ecological value, is a critical task for scientists, forest managers, and society.

What is stand-replacing fire?

Landscape heterogeneity is a key principle for conservation, adaptation, and management. Stand replacing, high severity fire, is a complement to fire refugia on the landscape. Stand-replacing fire kills most or all of the canopy trees in given location, dramatically altering forest conditions and providing an opportunity for early seral environments and species on the landscape.

What are mature and old forests?

Recent focus and reporting on mature and old forests was reinforced by the 2022 Biden Executive Order 14072. A key take home for mature and old forests is that they exist and develop in many flavors and styles, varying in their geography. Some general bins we consider in our work are “dry” forests, “moist” forests, and “cold” forest archetypes.

Selected literature resources

  • Krawchuk, M.A., Hudec, J., Meigs, G.W. 2023. Manager's brief: Integrating fire refugia concepts and data into vegetation management decisions. A case study on the Gifford Pinchot National Forest, Little White Salmon Project Area. 20 pages (pdf)
  • Naficy, C.E., G.W. Meigs, M.J. Gregory, R. Davis, D.M. Bell, K. Dugger, J.D. Wiens, M.A. Krawchuk. 2021. Fire refugia in old-growth forests—Final report to the USGS Northwest Climate Adaptation Center. Oregon State University, Corvallis, OR. 39 pages (pdf)
  • Downing, W.M., Meigs, G.W., Gregory, M.J., and Krawchuk, M.A. 2021. Where and why do conifer forests persist in refugia through multiple fire events? Global Change Biology 27(15):3642-3656; https://doi.org/10.1111/GCB.15655
  • Meigs, G.W., Dunn, C.J., Parks, S.A., and Krawchuk, M.A. 2020. Influence of topography and fuels on fire refugia probability under varying fire weather in forests of the US Pacific Northwest. Canadian Journal of Forest Research; https://doi.org/10.1139/cjfr-2019-0406
  • Morelli, TL., Barrows, C., Ramirez, A., Cartwright, J., Ackerly, D., Eaves, T., Ebersole, J., Krawchuk, M.A., Letcher, B., Mahalovich, M., Meigs, G. Michalak, J., Millar, C., Quinones, R., Stralberg, D., Thorne, J. 2020. Climate change refugia: biodiversity in the slow lane. Frontiers in Ecology and the Environment 18:228-234. Special Issue on Climate Change Refugia; https://doi.org/10.1002/fee.2189
  • Krawchuk, M.A., Meigs, G.W., Cartwright, J., Coop, J.D., Davis, R., Holz, A., Kolden, C., Meddens, A.J.H. 2020. Disturbance refugia within mosaics of forest fire, drought, and insect outbreaks. Frontiers in Ecology and the Environment 18:235-244 Special Issue on Climate Change Refugia; https://doi.org/10.1002/fee.2190
  • Downing, W.M., Krawchuk, M.A., Meigs, G.W., Haire, S.L., Coop, J.D., Walker, R.B., Whitman, E., Chong, G., Miller, C. 2019. Influence of fire refugia spatial pattern on post-fire forest recovery in Oregon's Blue Mountains. Landscape Ecology 34:771-792; https://doi.org/10.1007/s10980-019-00802-1
  • Meddens, A., Kolden, C., Lutz, J., Smith, A., Cansler, C., Abatzoglou, J., Meigs, G., Downing, W., and Krawchuk, M.A. 2018. Fire refugia: what are they and why do they matter for global change? BioScience 11; https://doi.org/10.1093/biosci/biy103
  • Meigs, G., and Krawchuk, M.A. 2018. Composition and structure of forest fire refugia: what are the ecosystem legacies across burned landscapes. Forests 2018, 9(5), 243; https://doi.org/10.3390/f9050243
  • Krawchuk, M.A., Haire, S., Coop, J.C., Parisien, M-A., Whitman, E., Chong, G., Miller, C. 2016. Topographic and fire weather controls of fire refugia in forested ecosystems of northwestern North America. Ecosphere 7(12) e01632; http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1632/full