Thursday, May 18 is the 20th anniversary of Mount St. Helen's eruption in 1980. How is the mountain recovering? What types of vegetation have grown in areas wiped out by lava and ash? What are expectations for future growth?
For the last 10 years, Washington State University Vancouver Biology professor John Bishop has been asking those questions and studying the reemergence of life on Mount St. Helens. His work takes place in the most devastated area on the mountain's north side, between the crater and Spirit Lake, named the Pumice Plains.
"There was no biological legacy left," Bishop said. "Plants, animals, bacteria and organic matter were all blown away, burned or buried by rock."
In 1981, a single lupine plant (Lupinus lepidus) was found in the Pumice Plains much to the surprise of ecologists. This plant was several kilometers from any surviving vegetation. According to Bishop this was amazing considering lupine seeds are rather large without adaptation for dispersal. The question of how the seeds were dispersed still remains.
So a lupine was found, what does this mean for the regrowth of vegetation on Mount St. Helens? Lupines are part of the legume family and add nitrogen to the soil enabling plant growth.
"It's much like you plant beans or peas in your garden to replenish the soil," Bishop said. "Lupines add nutrients back into the ecosystem. Most plants couldn't live here [the plains] without the lupine, although that has changed by now."
Today lupine patches more than 20 acres in size exist on the Pumice Plains and new vegetation has grown in areas where lupine first settled. Lupine was thought to act as an "ecosystem engineer" accelerating and encouraging revegetation.
"People had high expectations for lupines to spread but this didn't really happen," Bishop said. "As a graduate student in the early '90s, I saw that the lupine weren't spreading and became interested in why. I found lupines here and there, but they weren't flourishing like the original patch. Now a lot of things like to eat lupine. I found that insects were preventing lupines from reproducing so fast. They were running the revegetation show."
What Bishop found were caterpillars. Caterpillars were boring and living in the root of lupine plants, feeding on lupine seeds and weaving little protective tunnels out of leaves and gravel.
Bishop's work in this area focuses on primary succession--an ecological term for starting from scratch.
"Our work is one of the first examples of herbivores controlling revegetation. The larger question is whether herbivores in general control plant populations," Bishop said.
Bishop's other research on Mount St. Helens has focused on the evolutionary impacts of colonization and the "founder effect."
"When a new population is started from a limited group it is capable of causing radical genetic changes in the population. The founders may not represent what was there before. This means that when we look at the set of new patches, each patch differs genetically from the other. In theory, this could cause patches to respond differently to natural selection, and end up on different evolutionary trajectories," he said. "Lupines on Mount St. Helens do experience strong natural selection. However, in reality the founder effect may not matter on Mount St. Helens, because the effect only lasts a few generations before it's wiped away by pollinators, which move between patches and homogenize them."
According to Bishop, although the founder effect might not mean much for Mount St. Helens, it could be more important on a larger scale.
"Right now we're investigating whether Lupinus lepidus found on Mount Adams, Mount Hood, Mount St. Helens and Mount Rainier differ from each other. These places are like islands of habitat for this plant, it isn't found on most smaller mountains in-between these volcanoes."
Currently Bishop is also researching why there are no herbivores in the center of the lupine patch. At the edge of the patch, where the number of lupines thins out, more herbivores are found.
This may have to do with the addition of new trophic levels as new plant and animal communities form. Lupine embodies the first trophic level, which brings life through revegetation. Caterpillars feeding on the lupine make up the second trophic level, while birds, wasps, ants, spiders or anything eating the caterpillars make up the third trophic level.
During the summers, Bishop makes a two-day trip to Mount St. Helens about every 10 days. He logged about 20 to 30 days on the mountain last year. Students in WSU Vancouver's biology, environmental science and natural resource science programs, have the opportunity to participate in Bishop's field research. He had six student helpers last summer. Bishop received his Ph.D. from University of Washington in 1996 and joined the WSU Vancouver science faculty in 1998.
For more information on Mount St. Helens and John Bishop visit the following web sites: John Bishop's Research at Mount St. Helens: www.vancouver.wsu.edu/fac/bishop/homepage/Mount%20St.%20Helens.htm
WSU Vancouver's "Natural Catastrophe & Environmental Change in the Pacific Northwest: Lessons for the New Millennium" Lecture Series: www.vancouver.wsu.edu/programs/sci/disturbance.htm
Mount St. Helens National Monument: www.fs.fed.us./gpnf/mshnvm/
Cascades Volcano Observatory: http://vulcan.wr.usgs.gov/Volcanoes/MSH/NatMonument/framework.html
Volcano Cam: www.discovery.com/cams/sthelens/sthelens.html
Volcano World's Mount St. Helens Page: http://volcano.und.nodak.edu/vwdocs/msh/msh.html
The above story is based on materials provided by Washington State University. Note: Materials may be edited for content and length.
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