In the heart of fire-swept Trione-Annadel State Park, blackened columns of Douglas Fir, bare exposed earth, and the ghostly gray limbs of oak, madrone and bay still stand on the steep ridges and rolling hillsides between Oakmont and Bennett Valley.
Amid the devastation, meadows have sprouted with new green grass, and patches of tiny, orange, cup-like Anthrocobia — mushrooms that appear only after fire — have emerged among the white ashes, a strange splash of color amid the black and white landscape.
But the regeneration of the forest itself hangs, literally, by a delicate thread.
Down in the smoke-scented soil, beneath the dark char and white ash, tiny tendrils known as mycelia, thin as spider silk, are spreading. And their survival is key to the restoration of the woodland giants towering overhead.
In winter, when the rains come to California, some of these important forest dwellers betray their presence, sending up the mysteriously shaped and colored fruiting bodies we know as mushrooms.
But the fungus below them, the invisible living organisms that bear the mushrooms, are busy all year.
If we could see them, they’d be everywhere, an interwoven network of microscopic filaments, running through the layers of soil, within the leaf litter, beneath bark and in the living wood, and in everything that’s decaying.
At UC Berkeley, Tom Bruns, a researcher and fungus expert, or mycologist, has spent decades studying the hidden world of fungi in the wild, and their relationships with living plants.
“There’s a lot we don’t know,” he said, “but we now estimate 90 percent of all plant species live in association with fungal partners. They’re absolutely everywhere.”
And, without their fungal partners, it’s now known, many seedlings and trees will simply not survive.
The mycorrhiza fungi send their filaments out into the surrounding soil, gathering water and essential nutrients like nitrogen and phosphorus, which they transport back to the tree. Their branching mycelia are so incredibly fine that a cubic inch of soil can contain a mile or more of them. As a result, they extend the tree’s reach to critical food and water by ten to 1,000 times.
In exchange, Bruns explained, the tree provides them with sugars and carbon, which the growing fungus can’t produce themselves.
“Up to 20 percent of the sugar energy and fixed carbon produced by tree leaves using sunlight, is transported to the fungal mycorrhiza,” Bruns said, adding that individual types of trees and plants can each have their own particular fungal partners.
And what’s more, this so-called “wood-wide web” has recently been found to connect trees and stands of forest together. In 2016, researchers in Switzerland tracked the movement of tracers, and discovered that carbon absorbed by the leaves of one tree appeared in the tissues of separated neighboring trees, transported there by fungus pipelines.
So, what happens to this essential, delicate fungal network when the forest catches fire?
Most of them are destroyed and disappear, Bruns said, depending on how hot the fire burns, and for how long. But, he noted, many species found here have adapted to the California ecology, which is prone to regular fires.
Here, burning is a natural part of the life cycle of forests and plants. And the fungi have a few survival tricks up their sleeve.