Ahead of Earth Day, peek inside the living laboratory where redwoods meet modern science

Santa Cruz would not be the same without its redwood forests.

If these forests disappeared, countless species, such as banana slugs, marbled murrelets and mountain lions, would lose their homes. Fog patterns would change, making the landscape warmer, since redwoods soak up fog in their leaves then drip the excess to the ground, increasing the humidity so fog can linger longer. Locals and visitors would not be able to melt their stress away on a hike through the towering rich red bark of these ancient trees.  

As wildfires and other threats challenge California’s redwood forests, scientists and Indigenous leaders are working to understand and preserve the iconic trees by using San Vicente Redwoods, near Boulder Creek, as a living, breathing laboratory for both cutting-edge science and traditional Indigenous ecological practices.

Purchased in 2011 by the Sempervirens Fund, Peninsula Open Space Trust, Land Trust of Santa Cruz County and Save the Redwoods League, the 8,532-acre San Vicente Redwoods is more than just a beautiful place to spend an afternoon. It is also a real-life testing ground for innovative forest management techniques. 

Among those techniques is an imaging technology that helps detect a redwood tree’s internal defects to better understand its health after a blaze like the 2020 CZU Lightning Complex fires.  

Sound waves map tree health

Redwood bark is so thick that it usually protects the living wood on the inside of the tree from fire, even if the outside gets charred. But after the CZU fires, coniophora fungus, a group of fungus that can rot the living part of a tree, started to infect the burned redwoods that were left standing.

Redwoods are normally resistant to fungal decay, but this uncommon fungus became a growing problem after the fires when wounds to the bark let fungal spores into the inner wood. The fungus can degrade the interior, living wood, affecting its ability to move water and nutrients and reducing its quality for harvesting. 

Greg Gilbert, a professor of environmental studies at UC Santa Cruz, uses a technology called sonic tomography to look inside the redwoods. The technology uses sound waves to create a picture of the inside of a tree. This allows him to see where the fungus has eaten away at the tree.  

“The trees are the structure of an ecosystem that supports so many things. But inside all trees, no [matter] how healthy they look, all have fungi growing in them,” Gilbert said. “Understanding what the fungi are doing to the trees gives us a good idea of what to expect with the changes in the forest.” 

The team, led by Ph.D. student Liz Rennie, attached nails with sonic receptors around the tree. They then hit the top of each nail with a hammer to send sound waves through the tree. The sensors measure how long it takes for the sound waves to travel to the other nails around the tree. These differences in speed let the researchers create a cross-section of the tree that shows where the sound traveled faster or slower. Sound travels quickly and evenly throughout a healthy tree, while decayed wood makes the sound waves go slower. This cross-section can then show the location and severity of decay.  

Other methods of checking for fungal infection involve making wounds on the outside of the tree to inspect the sapwood, the living tissue on the outer ring of the tree. Sonic tomography is minimally invasive and doesn’t harm the tree, but it would take too long to do to every tree. The researchers hope that by seeing how decay changes the inside of a fire damaged tree, they can better understand how scorched bark lets fungal infection inside the tree.  Their goal is to match the damage on the outside of the bark to the level of decay on the inside, so foresters can more easily assess potential decay.   

Gilbert has been using this technology to study trees in the tropics for 35 years. He brought his work locally to study the trees on the UC Santa Cruz campus. After the CZU fires, he brought his expertise to San Vicente.  

“When the fires happened [it] became apparent that we needed to spend some time looking at what was going on there. It was like a wonderful opportunity to work with the foresters and [do] work that’s close to home,” Gilbert said. 

Other research projects at San Vicente include studying the impact of watershed health and salmon habitat after removing the Mill Creek dam in 2021. The dam was blocking sediment and other nutrients from moving downstream. Removing the dam and adding “large woody debris” (pieces of trees) have improved the habitat for steelhead and coho salmon. Elijah Catalan, a Ph.D. student at UCLA, uses environmental DNA to see if the salmon are benefiting from this change. Much like humans leave hair and skin cells wherever they go, animals also leave DNA samples in their environment. Researchers hope to see if improving the habitat expands the salmon’s range.  

Indigenous knowledge

The San Vicente Redwoods are the historical lands of the Awaswas-speaking Cotoni people. Today, the Amah Mutsun Land Trust works with the coalition of land-trust partners to care for and protect this land on behalf of their relatives and common ancestors. 

“The San Vicente Redwoods can be this area where it is this living laboratory, where we want to bring back Indigenous views of landscape management with some of these other Western views of management of the forest,” said Alec Apodaca, cultural resources program manager at the Amah Mutsun Land Trust. 

Through their historical ecology and archeology work, researchers learned that Native presence there goes back at least 5,000 years. This lets the land trust better understand how these lands were used, what that environment looked like and what plants the Native people valued for food and cultural uses. This knowledge can serve as a pathway to inform restoration work that can revitalize native species.  

Tribal practitioners lead efforts in identifying and protecting cultural sites. “It’s really to highlight that deep legacy of Indigenous peoples and their deep connection to the land by bringing back those Indigenous stewardship practices [such as cultural burning],” said Apodaca.  

Cultural burning is a low-intensity prescribed fire performed by Indigenous people and informed by traditional ecological knowledge. It builds wildfire resilience and is used to promote the growth and health of culturally significant native plants – such as medicinal, basketry and food plants.  

Without active, informed management, these areas and the diversity of plants and wildlife they house could be lost to future generations, said Beatrix Jiménez-Helsley, Sempervirens Fund’s natural resource manager.

Walking among the towering trunks of Sequoia National Park for the very first time inspired her to devote her time to conservation work – she now co-manages the San Vicente Redwoods forest. 

“It was lands like this that inspired me to care,” Jiménez-Helsley said. She hopes that when others visit San Vicente, they are also inspired to protect the land and get others to care for it as well. “I don’t care if someone remembers my name in the future, but hopefully [there is still] that legacy of all the work that’s happened.”

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