Study Finds Forest Regeneration In Lassen Volcanic National Park After Dixie Fire

While a research team worked to examine a stratified sample of plots in Lassen Volcanic National Park in California in 2021, the Dixie Fire arrived, growing into a nearly 1-million-acre blaze that devastated parts of the park over 104 days. The researchers had been studying how the forest that’s hands-off to residents and most fire-suppression measures had recovered from naturally occurring forest fires as far back as the mid-1980s.

The Dixie Fire halted their research efforts, but they ultimately found an opportunity in the fire’s aftermath. “The Dixie Fire rolled through and just blew our research project up,” said Alan Taylor, a professor emeritus of geography at Pennsylvania State University. “But it then gave us a chance to see how these massive and ever-increasing mega fires are impacting the forest. We wanted to know if and how the forest would recover after this extraordinary event.”

In 2022, the team altered their research objective and now wanted to see how the same landscape responded to extreme wildfire, and study how prior fires influenced chances of forest recovery. Their research (attached) found that despite more than 40 percent of the Dixie Fire burning at high severity, the forest showed signs of regeneration.

Just after the Dixie fire, 32 percent of the plots in the park had at least one seedling, and about half were considered “stocked,” a label the U.S. Forest Service applies when a plot is deemed likely to make a full recovery. Of all seedlings in the plots in 2021, 19 percent survived the Dixie fire.

The researchers also discovered that plots on steeper and wetter sites, farther from forest edges, with lower ground cover, and burned twice by previous fires rather than once before the Dixie Fire stood a stronger chance of having seedlings survive. Moreover, regeneration was less likely to persist where more ground cover was consumed by the Dixie Fire because that causes fires to burn hotter.

“In the past few decades, there has been a large increase in areas burned by wildfires, and these wildfires are now burning over areas that burned before,” Taylor explained. “Factors contributing to the persistence of forest regeneration in this overlapping mosaic of reburns is poorly known, and this research provides insights on where forest management activities could be focused to improve persistence of regeneration through reburns and new regeneration after fires.”

Despite the extreme temperatures created by the Dixie Fire, researchers found only about half the fire’s path resulted in a total loss of tree canopy.

“We’re seeing more high severity fires,” said Lucas Harris, a co-author of the study. “It’s a really important question whether forests are able to recover from these fires, and this research shows in many areas that they are.”

The study demonstrated how lessening fuels at forest edges and in large areas of high severity fire where fire-killed trees have fallen to the forest floor can lead to greater rates of forest recovery. Fuel reduction treatments during the Dixie Fire were also able to save many of the facilities and structures that were treated in the park.

“When you have a landscape in which you’re concerned about mega fire, which have become more common, the use of smaller scale, controlled fires under moderate weather conditions could offer very real protective benefits when you inevitably do have a larger scale disturbance,” said Dani Niziolek, a lead author on the research.