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As a wildfire researcher, Angie Liotta has been to some of Washington’s most rugged areas. She and her crew often rely on animal trails and bushwhacking to reach target locations to collect data.

This year they are returning to places across the state that burned at least a decade ago to gather new information about the trees and plants that either survived or established after our region’s most catastrophic wildfires. Sometimes the work is a slog, requiring long treks through remote areas. But often they find surprises that inspire awe and hope — like a massive ponderosa pine, alive and thriving despite half of its trunk being burned.

“I absolutely love seeing what has survived a fire. To me, that’s the coolest part of this work,” said Liotta, a doctoral candidate in the Harvey Lab at the University of Washington’s School of Environmental and Forest Sciences and a Guardians of the Wild fellow.

On the tail end of another record summer of devastating wildfires in Washington, Liotta hopes her research can help other scientists and land managers better predict which areas are most at risk of losing large swaths of trees when fires move through, and which areas have built some resilience to fire. This information could help managers prioritize actions like prescribed burning and thinning in the most at-risk areas to foster healthier landscapes that are more resilient to fires.

Liotta is creating a tool for land managers across the western U.S. to be able to input basic data about a section of land and get back detailed information about that area’s vulnerability to fire, even down to an individual tree’s risk of mortality. 

The goal with this fire resistance index is to have a publishable tool, that will be open to the public and land managers alike, that could essentially calculate fire resistance and then estimate potential tree mortality,” Liotta said.

Wildfire has always played an important role in forest ecosystems, but a century-long policy of fire suppression has caused areas with historically frequent-fire forests to build up excess fuels — dead branches, brushy undergrowth, smaller trees and more. Historically, drier areas like much of eastern Washington saw low-intensity fires move through on a relatively frequent basis. These burns allowed larger trees like ponderosa pines to thrive while the understory was kept in check, allowing the landscape to maintain a healthy relationship with fire. 

Years of fuel buildup combined with increasingly hotter, drier conditions have sparked the high-intensity wildfires that we’ve experienced frequently in the past 20 years. Sometimes these fires kill most of the trees in their wake. This sometimes devastating result is why land managers now use treatments such as thinning and prescribed burning to deal with dense forests. They also let some wildfires burn, provided they aren’t threatening communities.

“A lot of evidence is pointing to the fact that we’ve always had a lot of fire on these landscapes, but I think there are a few things that are quite different now,” Liotta said. “We have denser forests than we would have had. We have more people in these areas than would have been there historically.

We’re trying to answer a big piece of the puzzle of how to get ahead of the game — when and where can we manage a forest before a fire goes through? That way, we know that when a fire does happen, it can provide more beneficial outcomes.”

Understanding what happens in forests after large wildfires is important for developing a strategy to manage landscapes going forward.

This past summer, Liotta and her team traveled to areas across central and eastern Washington where five different wildfires burned at least 10 years ago, all sites first studied by the Washington State Department of Natural Resources (DNR). They carefully documented all plants, dead and alive, in each of the many 30-meter sections, noting things such as grass cover, downed wood, dead snags, dominant shrubs, trees that survived and new tree seedlings.

“We want to know how much fuel is in a forest so we can better project how that forest would burn again if there were a reburn,” Liotta explained.

It was grueling work, even for this experienced crew. Their schedules and plans changed often due to unpredictable fire and smoke activity across the state in July and August, but the team was still able to gather a wealth of useful data. 

“This work is a key piece in the broader puzzle of understanding the effects of fires on forests now, and what that might mean going into the future,” said adviser Brian Harvey, the Jack Corkery and George Corkery Jr. Endowed Professor in Forest Sciences. “Building this understanding requires integrating different ways of testing how, when, where and why forests will be resilient to fire, and the field data that Angie has been working with are important for gaining on-the-ground observations of fire effects as well as helping us tune insights we can get from satellites or simulation models.”

These field efforts built upon similar data collected by DNR and the Harvey Lab five years after these fires originally burned. During the first part of her PhD, Liotta led the initial analysis of this data and produced a comprehensive report with her DNR collaborators that is currently guiding post-fire management priorities across the state. The new data collected this summer will add a longer timeframe to this dataset.

Angie has really pushed the envelope with this dataset and has been incredibly creative in its utility,” said collaborator Josh Halofsky, a research scientist at DNR. “She’s taking it in many different directions that we think will be really informative and useful. So we’re really excited.”

This latest trove of data is helping Liotta develop a wildfire resistance tool. Looking at which trees lived through recent fires — and considering which traits or factors helped them survive — is essential to predicting future outcomes, she said. 

“I’m identifying areas that have high fire resistance based on tree species, tree size and other traits that are related to surviving wildfire, and then I’m essentially predicting the percent of tree mortality of these plots. So, for example: Based on what we know about this area, do we expect it to have 10, 20 or 30 percent tree mortality?,” Liotta explained.

The tool is calibrated to be used across the western U.S. and takes into account almost 30 different tree species, including the region’s most common conifer trees. DNR scientists say fire resistance scores could be used in the future as another metric for assessing forest resilience in stands of trees over time.

“My understanding of this tool is it will enable a more comprehensive look at what these fires are doing, in terms of how they change forests,” said Dan Donato, a research scientist at DNR who also works closely with Liotta. 

Wildfire does a lot of things. It can certainly cause damage in human communities, but it also does a certain amount of ecological work. Partial burns can increase forest resilience by selecting for the more fire-resistant elements for when the next fire comes. Angie’s work I believe will help quantify that change.”

Liotta’s current work is funded by the Guardians of the Wild Fellowship, which supports University of Washington graduate students who are working in environmental or wildlife conservation or living natural resource management, including protecting wild places. The fellowship is managed by the UW College of the Environment and funded by donors and the nonprofit organization Re:wild. 

Story by Michelle Ma. Photography by Mark Stone.