Forest Ecosystems
JB: This is Earth and Sky. On May 18, 1980, a volcano in Washington State – Mount St. Helens – erupted.
DB: It destroyed 230 square miles – about 500 square kilometers – of forest. What was left was a gray and brown landscape littered with dead trees and covered with ash and pumice.
JB: The greatest surprise to scientists surveying the area following the eruption was the discovery that many plants had survived. The early spring timing of the eruption meant that there were still snow banks on high mountain ridges. The snow sheltered some plants from the full effects of the blast.
DB: Later, the surviving plants were joined by colonizers from wind-blown seeds. In the past ten years, shrubs and trees have arrived. Forest experts say that within a hundred years a mature forest will probably cover most of the area. Within two hundred years it should begin to resemble the old-growth forests that existed before the eruption.
JB: But the landscape just north of the volcano is about a hundred years behind. That’s because no biological legacies of any kind survived the eruption. But even here, recovery has started. Today it’s mostly covered with flowering prairie lupine. Today’s show was made possible by the National Fish and Wildlife Foundation, in cooperation with the U.S. Forest Service. We’re Block and Byrd for Earth and Sky.
The following individual(s) were interviewed for today’s show. Our thanks to:
Peter Frenzen
Monument Scientist
USDA Forest Service
Mount St. Helens National Volcanic Monument
Dr. John Bishop
Assistant Professor
School of Biological Science
Washington State University
Vancouver, WA
The following books, articles and web sites were used in preparing this script:
Nineteen Years Later Forest Rebirth is Well Underway – Biological Research at Mt. Saint Helens National Volcanic Monument
Author’s Notes:
Lupines were suppressed by caterpillars for nearly a decade, but now escaped and exploded across the bare-rock landscape.
Animals have taken up residence in the developing forest, and they influence forest development. Elk clip off and uproot small trees. As they feed they deposit the seeds of grass and clover producing open, grassy meadows where, in the absence of elk, forests would grow. By excluding elk from fenced plots scientists are comparing forest development with and without large grazing animals.
The abundance of willow, an important component of plant succession at the volcano, appears to be heavily influenced by the presence of a tiny weevil. The adult weevil lays its eggs in the willow stem and the stem is either greatly weakened or killed as the developing larvae feed upon and girdle it.
Additional Teacher Resources
USDA Forest Service, Pacific Northwest Research Station, Science Findings: The Rule of Time and Chance: Mount St. Helens and Its Legacy of Knowledge
This article touches on the effects that the 1980 eruption of Mount St. Helens had on the surrounding ecosystem, and the subsequent discoveries made in the wake of the destruction. It then spans the course of 20 years and the shocking discoveries found by scientists in the recovery of both flora and fauna in the once devastated area.
USDA Forest Service, Mount St. Helens National Volcanic Monument: Mount St. Helens
This site is a great resource for information on several subjects concerning Mount St. Helens, including the natural history of the volcano itself, the history of the surrounding National Park, and the ongoing recovery of the forest ecosystem. It provides students with an opportunity to ?visit and discover’ the drama of an active volcano, learn about 25 years of ecological recovery, view digital photo images from before, during, and after the eruption and finally provides links to more information of the saga of the Mount St. Helens National Volcanic Monument.
USDA Forest Service, Mount St. Helens National Volcanic Monument Photo Library: 25 Years of Change
A page of photographic images with captions showing the vegetation around Mount St. Helens before and after its eruption in 1980.
