When Mount St. Helens erupted in 1980, its fiery blast of molten rock and scorching ash left miles of the surrounding landscape in ruins. Every plant, tree and living thing in its path was incinerated or buried under volcanic debris.
For scientists, this offered a unique natural laboratory to explore how life could begin anew on a landscape so thoroughly devastated.
What did the scientist do? They released gophers onto the mountainside.
The results were even more striking than the team had hoped. In just one day, the burrowing rodents began a chain reaction that would impact the soil’s health and biodiversity for decades.
A study published this week in Frontiers in Microbiomes reveals the lasting effects of this intervention, showing a persistent increase in beneficial microbes in the areas where gophers once dug, compared to nearby soil that had been left untouched.
"In the 1980s, we were just testing the short-term reaction," says co-author of the study Michael Allen, a microbiologist from the University of California. "Who would have predicted you could toss a gopher in for a day and see a residual effect 40 years later?"
Gopher theory
Once the debris from the explosion began to cool, scientists speculated that the humble gopher might play a vital role in rebuilding this harsh, inhospitable environment.
They theorised that as gophers dug through the ash, they could unearth buried bacteria and fungi essential for soil health.
"They're often considered pests, but we thought they would take old soil, move it to the surface, and that would be where recovery would occur," explains Allen.
A mountain transformed
In 1983, Allen and Utah State University ecologist James McMahon flew by helicopter to the experimental plots, now a harsh, pockmarked landscape of cooling lava and porous pumice.
At that time, only a handful of plants managed to eke out a precarious existence in these conditions. A few seeds, scattered by passing birds, had sprouted, but with little nutrients available, the seedlings struggled to survive.
On two designated pumice plots, scientists released a few gophers for a single day to observe how their digging might affect the ecosystem.
Within six years, the barren soil had transformed. These once-desolate patches now held over 40,000 thriving plants. In stark contrast, nearby land untouched by the gophers remained largely lifeless.
This remarkable resurgence of plant life was thanks to something invisible to the eye — mycorrhizal fungi. These microscopic fungi play a crucial role in healthy soil by forming symbiotic relationships with plant roots, which allows them to exchange nutrients and protect plants from pathogens. In barren environments, where nutrients are scarce, mycorrhizal fungi are invaluable, transporting essential elements like water and minerals directly to plant roots.
"With the exception of a few weeds, there is no way most plant roots are efficient enough to get all the nutrients and water they need by themselves. The fungi transport these things to the plant and get carbon they need for their own growth in exchange," Allen notes.
Magical microbes
The study also shed light on how these microbial networks affected other areas of the mountain’s recovery. On one side of Mount St. Helens, an old-growth forest lay under layers of ash. Initially, scientists feared that this thick coating would trap heat and destroy the needles of pine, spruce and Douglas fir trees, potentially leading to a forest collapse. However, the opposite happened.
"These trees have their own mycorrhizal fungi that picked up nutrients from the dropped needles and helped fuel rapid tree regrowth," explains UCR environmental microbiologist Emma Aronson, a co-author of the study. "The trees came back almost immediately in some places. It didn't all die like everyone thought."
In contrast, scientists also studied a section of the mountain that had been clear-cut before the eruption. With all mature trees removed from this forest, there were no dropped needles to nourish the soil’s microbes. The result? Little to no regrowth in the clear-cut area, even decades later.
"There still isn't much of anything growing in the clear-cut area," Aronson says. "It was shocking looking at the old-growth forest soil and comparing it to the dead area."
This extraordinary resilience highlights the intricate, interdependent relationships that sustain ecosystems. According to Mia Maltz, the lead author of the study and a mycologist from the University of Connecticut, it underscores the essential role of soil microbes in restoring disturbed landscapes.
"We cannot ignore the interdependence of all things in nature, especially the things we cannot see like microbes and fungi," says Maltz.
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