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Posted On: Filed Under: Biological Research

Effects of elk and deer on early forest succession at Mount St. Helens

The objective of this study is to determine the role of elk and deer in the recovery of both natural and managed vegetation following volcanic disturbance. Additionally, we are interested in documenting the influence of elk and deer on vegetation establishment in areas that received different levels of volcanic impact. This goal will be achieved through a network of exclosures that will allow cross-site comparisons.

 

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Population dynamics and habitat ecology of elk in the Mount St. Helens blast zone

Population dynamics and seasonal patterns of foraging behavior of elk in the northwest portion of the Mount St. Helens blast zone were investigated during the years 1982 through 1985. A combination of rapid vegetation regrowth, mild winters, restricted human access and low harvests allowed a rapid re-invasion and recovery of the elk population.

 

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Summer bird populations of upper subalpine zone of Mount St. Helens, Mount Adams, and Mount Rainier.

Species composition and abundance of summer birds in the upper subalpine zone of Mount St. Helens were compared to those of Mount Adams and Mount Rainier in order to document these populations as well as to examine effects of the May 1980 eruption on bird populations at the volcano.

 

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Observation of recolonization of amphibians and reptiles in North Fork Toutle River debris avalanche.

Various reports indicate in situ survival of or early migration of some amphibians into regions of the blast zone following the major eruptions on May 1980. Investigators observed salamanders, frogs and toads as early as 1980 and 1981 in areas of heavy ashfall northeast of the crater. Survival at higher elevations likely was favored by snow and ice cover and the fact that many animals were in hibernacula.

 

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Recovery of stream ecosystems following catastrophic disturbances

This study was conducted in the Clearwater basin of Mount St. Helens. Three projects within the study investigate recovery of trout and sculpin populations, tailed frog populations, and invertebrate populations. Trout were studied in the main channel of Clearwater Creek, and the effects of large woody debris in the stream on fish populations were examined. Trout populations were still low as of 1990, being one-tenth to 20% of that in undisturbed stream systems; this appears largely due to interruption of spawning in years following the blast and to continuing lack of spawning habitat. Trout densities were found to be higher in areas with lots of woody debris. The condition of trout was high throughout the stream in years since 1984 presumably due to rapid recovery of high abundance of invertebrate prey. By 1985 sculpin densities were as high as or higher than in undisturbed streams.

 

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Effects of pocket gopher (Thomomys talpoides) mounds on plant reestablishment processes.

This studydocuments that pocket gophers in the blast zone did survive the May 1980 eruption of Mount St. Helens, and they did have an effect on early plant re-establishment within the blast zone. One study site is approximately 20 km northeast of the volcano. This site received a layer of pumice and ash to an average depth of 12 cm in 1980. Vegetation on gopher mounds was compared to that on surrounding un-mounded soil surface. Findings show that species composition is different; there are more residual species on mounds, and seedlings on mounds are more likely to survive and contribute to future local population growth.

 

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Ecology of the tadpoles of the tailed frog (Ascaphus truei)

Data on the microhabitat parameters, especially pertaining to flow rate and substrate characteristics, of the stream-inhabiting tadpoles of the tailed frog (Ascaphus truei) were collected at two tributaries of Clearwater Creek at Mount St. Helens, Washington and at Parker Creek on Mary’s Peak, Benton County, Oregon. This is the only tadpole in North America that is highly specialized for maintaining position and feeding from algae while attached to rocks via an enlarged oral disc with many rows of labial teeth. Positions of tadpoles in the streams were correlated with oral morphology and associated anatomy. Because of the length of the larval period of Ascaphus, there are usually 2 to 3 yearly cohorts in the streams at one time. We hypothesized that the interaction of the abilities of the tadpoles to adhere to rocky substrates and the size of the tadpole would result in microhabitat segregation. Whether small or large tadpoles occupied fast versus slow water would depend on the growth pattern of the tadpole (drag) versus the changes of the adhesive abilities with size.

 

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Recovery of mycorrhizal associations on Mount St. Helens.

This work has studied the recovery of mycorrhizal associations on Mount St. Helens since the eruption in 1980. Mycorrhizal associations are symbioses between plants and fungi localized on the roots of plants. The fungi provide much of the nutrients utilized by the plants and the plants provide carbohydrates to the fungi. The associations on Mount St. Helens range from those plants that form facultative mycorrhizal associations, many herbaceous species including Lupinus lepidus, L., latifolius, and Epilobium angustifolium, to the coniferous trees that are obligately dependent on mycorrhizae.

 

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