The eruption of Mount St. Helens in 1980 scattered roughly 540 million tons of ash over an area of more than 22,000 square miles (57,000 square kilometers), according to the USGS. This blistering blast of lava incinerated life in the area, scorching the earth and turning the land to pumice. Researchers theorized that gophers could help restore the area, because they excavate beneficial microbes like bacteria and fungi.
Scientists decided to test this theory by briefly depositing gophers in the region about two years after the eruption, but for only 24 hours. They turned out to be incredibly beneficial to recovery. According to work recently reported in Frontiers in Microbiology, these benefits, from only one day, can still be seen now. The work compared areas where the gophers were deposited to places where there were no gophers introduced. The presence of the animals seems to have made lasting changes to the soil microbiome.
"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," explained study co-author and University of California Riverside (UCR) microbiologist Michael Allen. "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 forty years later?"
In 1983, Allen and colleague James McMahon took a helicopter to a location that had been affected by lava flow. On these pumice plots, there were few plants at the time, and while some seeds had been deposited by birds, the seedlings were struggling.
Once some local gophers were dropped onto two pumice plots for a single day, the area bloomed with life. These locations were home to about 40,000 thriving plants years later, while regions untouched by gophers was mostly barren.
This explosion of growth was made possible by mycorrhizal fungi, which can help plant root cells exchange nutrients and resources; shield plants from soil pathogens; and help plants take root and survive.
"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 said.
After the eruption, trees in an old-growth forest on one side of the mountain lost most of their needles. But the forest did not die. Instead, fungi in the trees were able to take up nutrients that fueled the regrowth of the trees, explained senior study author Emma Aronson, an environmental microbiologist at the University of California, Riverside. "The trees came back almost immediately in some places. It didn't all die like everyone thought."
Before the eruption, one side of the mountain had held a forest that was clearcut. There was nothing that contained fungi to help recovery.
"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," said Aronson.
This study has emphasized that microbes can be crucial to restoring lost plant life after a natural disaster. "We cannot ignore the interdependence of all things in nature, especially the things we cannot see like microbes and fungi," added first study author Mia Maltz, now a mycologist at the University of Connecticut.
Sources: University of California, Frontiers in Microbiology