An unhappy gopher and plant near the gopher enclosure fence in 1982. Credit: Michael Allen/ UCR.

Gophers kick-started decades of soil recovery around the scarred remains of Mount St Helens after its catastrophic 1980 volcanic eruption.

When Mount St Helens erupted in 1980, lava incinerated anything living for miles around.

As an experiment, scientists dropped gophers onto parts of the scorched mountain for only 24 hours. The benefits from that single day were undeniable – and still visible 40 years later.

Once the blistering blast of ash and debris cooled, scientists theorised that, by digging up beneficial bacteria and fungi, gophers might be able to help regenerate lost plant and animal life on the mountain. Two years after the eruption, they tested this theory.

The University of California Riverside’s Michael Allen said: “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.”

They were right. But the scientists did not expect the benefits of this experiment would still be visible in the soil today, in 2024.

A new paper details an enduring change in the communities of fungi and bacteria where gophers had been, versus nearby land where they were never introduced.

Allen, a microbiologist at UCR, said: “In the 1980s, we were just testing the short-term reaction.

“Who would have predicted you could toss a gopher in for a day and see a residual effect 40 years later?”

Gophers and plants thriving in the once barren area scarred by the volcanic eruption, 2012. Credit: Mike Allen/ UCR.

Slabs of porous pumice

In 1983, Allen and Utah State University’s James McMahon helicoptered to an area where the lava had turned the land into collapsing slabs of porous pumice.

At that time, there were only about a dozen plants that had learned to live on these slabs. A few seeds had been dropped by birds, but the resulting seedlings struggled.

After scientists dropped a few local gophers on two pumice plots for a day, the land exploded again with new life.

Six years post-experiment, there were 40,000 plants thriving on the gopher plots.

The untouched land remained mostly barren.

All this was possible because of what isn’t always visible to the naked eye.

Mycorrhizal fungi penetrate into plant root cells to exchange nutrients and resources.

They can help protect plants from pathogens in the soil, and critically, by providing nutrients in barren places, they help plants establish themselves and survive. 

Allen said: “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.”

Forest collapse? 

A second aspect of this study further underscores how critical these microbes are to the regrowth of plant life after a natural disaster.

On one side of the mountain was an old-growth forest. Ash from the volcano blanketed the trees, trapping solar radiation and causing needles on the pine, spruce, and Douglas firs to overheat and fall off.

Scientists feared the loss of the needles would cause the forest to collapse. But that is not what happened.

UCR environmental microbiologist and paper co-author Emma Aronson said: “These trees have their own mycorrhizal fungi that picked up nutrients from the dropped needles and helped fuel rapid tree regrowth.

“The trees came back almost immediately in some places. It didn’t all die like everyone thought.”

On the other side of the mountain, the scientists visited a forest that had been clearcut prior to the eruption.

Logging had removed all the trees for acres, so naturally there were no dropped needles to feed soil fungi. 

Aronson said: “There still isn’t much of anything growing in the clearcut area. It was shocking looking at the old-growth forest soil and comparing it to the dead area.”

These results underscore how much there is to learn about rescuing distressed ecosystems, said lead study author and University of Connecticut mycologist Mia Maltz, who was a postdoctoral scholar in Aronson’s lab at UCR when the study began.

She said: “We cannot ignore the interdependence of all things in nature, especially the things we cannot see like microbes and fungi.” 

The research is published in Frontiers in Microbiomes.