Restoring Giants from the Ground Up: A Story of Fire, Soil, and Sequoias
In the charred groves of California’s Sierra Nevada, silence has replaced the towering presence of some of the world’s largest trees. Once standing for thousands of years, these ancient giant sequoias have withstood centuries of fire—until now.
In just the past few years, wildfires, exacerbated by heavy fuel loads, warming temperatures and exceptional drought have killed nearly 20% of the world’s mature sequoias. Fires like the Castle Fire in 2020 and the KNP Complex Fire in 2021 burned hotter and more intensely than anything these forests had evolved to survive. And in some areas, something even more unsettling is happening: the groves are not growing back.
While these massive trees once relied on fire to open their cones and create space for seedlings, today’s megafires can potentially consume entire cone crops and leave behind soil that is too dry, too hot, and possibly too depleted of life to support new growth. Now, a team of scientists from the U.S. Geological Survey (USGS), the National Park Service, Stanford University, the University of Washington, in collaboration with other partners, is trying to figure out how to bring these forests back—starting from the ground up.
The Secret Life Beneath the Forest Floor
At the heart of the project is a tiny but powerful community: soil microbes. These fungi and bacteria live on and around tree roots, forming partnerships that help plants absorb water and nutrients, fight off disease, and tolerate drought.
“Without the right microbes, seedlings may struggle to establish,” says Dr. Courtney Creamer, a USGS scientist leading the research. “High-intensity fires may reduce the diversity or abundance of beneficial soil microbes, especially those that support plant growth. We want to know: can reintroducing those microbes help seedlings survive in tough, post-fire landscapes?”
To find out, the team is growing hundreds of sequoia seedlings in different soil mixes—some from unburned forests, some from severely burned sites. Some soils are treated with beneficial fungi like arbuscular mycorrhizal fungi (AMF), known to support root development and water uptake. The goal is to test whether microbial “boosts” can give seedlings a better shot at surviving after being planted back in the wild.
Mapping the Landscape, One Slope at a Time
But microbes are only part of the story. Where seedlings are planted may matter just as much as how they’re grown.
The researchers are using high-resolution terrain maps to classify the landscape into “moisture zones” based on slope, sun exposure, and proximity to water. Some areas hold moisture better—key for young trees facing California’s dry summers. By planting seedlings across these different zones and monitoring their success, the team hopes to learn which parts of the burned forest are most likely to support planted seedling growth. Placing each seedling where the soil, microbes, and moisture conditions are most favorable may further improve survival after catastrophic fire.
Replanting the Future
This isn’t just about saving trees—it’s about protecting ecosystems, cultural heritage, and climate resilience. Giant sequoias play a vital role in their environment, providing habitat, storing carbon, and inspiring awe in millions of visitors each year.
That’s why the project is deeply collaborative. The team is working with land managers, land stewards, and researchers in academic, government, and non-governmental organizations to ensure the work reflects shared values and benefits.
The stakes are high. If natural regeneration fails, and replanting doesn’t succeed, some sequoia groves could disappear altogether. But if this research can pinpoint where and how to restore them, it could guide reforestation efforts across the Sierra—and possibly inform efforts in other fire-impacted ecosystems. In a hotter, drier future, targeted restoration strategies like this may be increasingly important.
From microbes to mountainsides, the team is working to ensure that the next generation of sequoias takes root—not just for today, but for centuries to come.
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