Exploring post-fire environments

Each summer, communities throughout Oregon and the Pacific Northwest brace for wildfire, but this summer a team of researchers from Oregon State set out to find places that have already burned.

Graduate student Will Downing, working with Assistant Professor Meg Krawchuk, spent most of his summer in the Blue Mountains observing how conifer forests recover after sustaining fire and unravelling the role of fire refugia – those places in the burn mosaic where the forest canopy persists – in supporting forest recovery and maintaining landscape biodiversity.

“We go back to these fires that burned between twelve and fifteen years ago, where the dust has settled,” Krawchuk explains. “We’re looking at areas of refugia, places where forest canopy persisted despite the landscape surrounding them experiencing high-severity fire.”

Part of the challenge, Krawchuk says, is actually finding the locations.

“We do a lot of work before we go into the field looking at GIS layers,” she says. “We know what we think we’re going to find when we go out into the field, but sometimes what you see on the picture is different from what you see on the ground. We’re looking for particular conditions and inventory of species.”

Downing’s project focuses on dry mixed conifer forests, which dominate the landscape of the Blue Mountains. Similar research has been conducted, to develop models and test hypotheses about the forest recovery in burn mosaics, but not in the Blue Mountains, and not using the nuanced landscape metrics that Downing has developed to characterize fire refugia, and not examining on-the-ground composition of these forest fire refugia.

“This research is unique in its geographic focus and the questions we’re asking,” Downing says. “A baseline characterization of the structure and composition of fire refugia will help guide future research priorities and contribute to a deeper understanding of post-fire patterns of vegetation, and habitat for species inhabiting these burned landscapes.”

Krawchuk calls this project an example of basic field science.

“We’re not using really fancy tools or instruments,” she says. “Instead, we measure and count the trees and identify and record the species of plants in each of the areas.” The fusion of the field data with GIS and statistical analysis provides important information about burn mosaics, and the trajectory of forest communities after fire.”
Krawchuk and Downing think the landscape context of surviving seed source in post-fire refugia will tell them something about trajectories of forest recovery. Rather than measuring just the distance to nearest surviving tree as an estimate of seed source, which is what previous researchers have done, Downing is examining the seed source available in the surrounding neighborhood and discriminating by species. He thinks that more surviving trees in the neighborhood should mean higher probability of seedling recruitment.

“The presence of surviving seed source is particularly important for seed obligate tree species like ponderosa pine, Douglas-fir, and grand fir, because these species are not capable of vegetative reproduction,” Downing says. “We’re also interested in the broader plant communities that persist in these fire refugia. Fires leave a mosaic of severity across the landscape, and the composition and ecological function of low severity or unburned ‘refugia’ are key legacy features of fire.”

Like most of Oregon State’s research about historical and persistent wildfire, this study has implications for forest managers around the Pacific Northwest. Krawchuk and Downing will spend much of the next academic year analyzing their data and looking for real-world solutions for sustainable forest management.