After decades of fire suppression in California, new research from the University of California, Berkeley, suggests that prescribed burning can improve forest health and help store carbon in large, fire-resistant trees over time. The study tracked forest plots at the Blodgett Forest Research Station in the Sierra Nevada for more than 20 years, applying different management techniques including controlled burns and restoration thinning.
The researchers found that while prescribed burning releases carbon dioxide immediately after a burn, repeated use of controlled fire supports the growth of larger trees and increases the forest’s long-term productivity. “Over time, we found that the productivity of unmanaged tree stands decreased, likely due to increased competition and climate stress. Meanwhile, prescribed burning helped maintain large, fire-resistant trees, eventually increasing the productivity of these stands,” said study lead author Yihong Zhu, a graduate student at UC Berkeley. “We wouldn’t be able to detect such a benefit had we not been able to monitor these stands over 20 years and three entries with controlled fire.”
The findings may inform policy decisions as California aims for net zero carbon pollution by 2045. Study senior author John Battles, professor of forest ecology at UC Berkeley, stated: “Nature-based climate solutions were a big focus of the 2024 Paris Climate agreement, and either maintaining or increasing forest carbon is one of the most cost-effective strategies. We found that, with some management, you may lower the total carbon storage of a forest, but you make it safer from loss from wildfires or pathogen outbreaks. We call it stable carbon.”
Researchers compared plots managed with prescribed burns to those left untouched. While control plots stored more total carbon overall during the study period, areas treated with regular burns saw an increase in net productivity after multiple treatments—almost offsetting initial losses from released carbon.
“After the first burn, the net productivity of those plots was really low and the controls looked a lot better,” said John Battles. “But by the third burn, the patterns had switched.”
To assess changes in carbon storage and release across treatments—including big trees down to decaying pine needles—the team conducted detailed fieldwork and lab analysis. “We looked at big trees, we looked at little trees, we looked at shrubs, we looked at different fuel classes, and then we checked how they changed,” said Battles. “It really is just like a massive accounting job, except we’re not measuring money, we’re measuring carbon.”
Fire suppression has allowed smaller shade-tolerant species such as incense cedar and white fir to proliferate in Sierra Nevada forests—species that can act as fuel ladders for severe wildfires. Prescribed burning helps reverse this trend by favoring larger species like ponderosa pine.
“We’ve always wondered if we could restore these ecosystems to a more functional state—lower density and more frequent fire—do we eventually see a bonus? Do we get that golden nugget? And in this work, we were able to actually measure it,” said co-author Scott Stephens.
Previous research by this group indicated that combining mechanical thinning with prescribed burning most effectively reduces wildfire risk but also results in higher immediate carbon emissions. The two studies together offer guidance for communities on choosing appropriate management approaches based on local priorities.
“We’ve got to get these treatments out there,” Battles said. “Some treatments might be better than others in certain situations, but now we’ve made the trade-offs explicit so we can pick the right approach.”
Other contributors include Daniel Foster, Brandon Collins, Robert York, Ariel Roughton and John Sanders from UC Berkeley; Emily Moghaddas from the U.S. Department of Agriculture Forest Service.
