Biological Research

Posted On: Filed Under: Biological Research

Distribution of Van Dyke’s salamander (Plethodon vandykei).

A survey is being conducted to document the distribution of Plethodon vandykei and factors correlated with its occurrence. This will entail visiting all known populations in Mount St. Helens National Volcanic Monument, searching for additional populations in the Monument, and recording aspects of the habitat associated with each population visited. By providing a more complete picture of the distribution of the salamander than is presently available, the proposed study will permit monitoring and further study of this species’ populations and also enhance understanding of its habitat associations.

 

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Posted On: Filed Under: Biological Research

Fungal and mycorrhizal succession in the Mount St. Helens devastation area

Samples of tephra deposits from the May 1980 eruption showed no mycorrhizal fungi in 1980 to 1985. Samples of buried soils and mudflow soil, however, showed that mycorrhizal fungi did survive the volcanic disturbance. Plant succession patterns in areas of tephra deposits reflect the distribution of mycorrhizae in that plants that resprouted or germinated from old soils where mycorrhizal fungi were present were much more successful than seedlings that germinated in the tephra that lacked these fungi. Mudflow soils and old soils that were exposed as when tephra eroded were initially much more conducive to revegetation at least partly because these soils contained the mycorrhizal fungi.

 

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Forested plant association classification

This work, which includes sample sites on the Mount St. Helens National Volcanic Monument, extends across forested areas of the entire Gifford Pinchot National Forest.

 

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Studies of hillslope erosion in the eastern part of the blast zone.

We have been measuring tephra/soil erosion rates in the Smith, Bean, Clearwater, Upper Green River areas of the eastern part of the blast zone. Debris slides and debris flows have been inventoried based on field observations and interpretation of aerial photographs for the 1967 to 1984 period. Sheet and rill erosion was measured with arrays of erosion pins. Repeat photography of hillslope, channel, and revegetation changes has been done at a variety of locations. The intensity of measurements has been reduced through time, but all sites could be revisited and longer-term trends in erosion rates estimated.

 

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Sedimentation and geomorphic changes following the 1980-1983 eruptions of Mount St. Helens

Reduced infiltration and burial of surface roughness elements, together with the loss of root strength and reduced evapotranspiration associated with blast-toppled vegetation have dramatically accelerated erosion of blast-affected hill slopes. Other investigators have found that rill erosion rates were initially higher than the yearly average, but then declined sharply so that rill erosion rates during the second year were only 5 percent of the average first year rate. Initial rates of sheet erosion were substantially higher than the average rate for the year, but the rate of decline was not as pronounced as in the case of rill erosion (Swanson, et al., 1983b).

 

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Cave biology in the Mount St. Helens Cave Basalt lava flow

This study seeks to establish an inventory of species inhabiting and using lava tubes and caves in the Cave Basalt lava flow. Bat populations in caves are dominated by Plecotus townsendii. Of small mammal species inhabiting or using caves, deer mice (Peromyscus maniculatus) are most wide spread. Few amphibians were observed; the most significant amphibian finding was a population of Larch Mountain salamander (Plethodon larselli). 256 invertebrate species of which approximately 100 species are arthropods have been collected in caves.

 

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Effects of May 1980 eruption on soil arthropods — a preliminary look

This preliminary investigation sampled soils in the blast area and blowdown zone in September 1980 for soil arthropods. Predictably, where disruption of pre-eruption ecosystems was most thorough — debris avalanche, pyroclastic flow, blast zone — no soil arthropods survived. In the blowdown zone, by contrast, soil arthropod populations were unaffected largely because they were protected by snow cover at the time of the eruption.

 

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Limnological monitoring of some lakes of the Mount St. Helens National Volcanic Monument.

The monitoring program will sample the phytoplankton and zooplankton communities of Castle and Coldwater Lake. The sampling program will also include water samples which will be analyzed for soluble reactive phosphorus, total phosphorus, nitrate, major ions, dissolved oxygen, and conductivity. Temperature and water transparency will also be observed. The data will be analyzed to determine the structure of phytoplankton and zooplankton communities in these two lakes and the possible impacts of fish introduced into Coldwater Lake.

 

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Post-eruption species selection and planting trials for reforestation of sites near Mount St. Helens

This study monitored survival and growth of seven conifer species planted with shading and fertilization treatments on disturbed sites at Mount St. Helens. Seedlings were planted on six low-elevation sites and five high-elevation sites which represented a variety of post-eruption conditions.

 

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Ant-plant interactions at Mount St. Helens

Within the blowdown zone of Mount St. Helens, Formica pacifica is the most common ant species. From studies during the summer of 1991 patterns were observed in the spatial dispersion of F. pacifica nests and also in the plant species present on the middens of these nests. Formica pacifica is less active within species rich vegetation patches than in exposed areas. Studies in 1992 will investigate whether F. pacifica nests are more common along the edges of vegetation patches. Other studies will investigate the presence of Hypochaeris radicata (false dandelion) on the middens of these nests. The wind born seeds of H. radicata may have difficulty establishing on the nutrient poor tephra. Ant middens may provide suitable sites for these plants to establish. Soil brought to the surface during nest excavation and the collection of plant and insect parts may add nutrients to the substrate of ant middens. Once established above an ant nest, plants would begin to cause shading of the nest. The resulting decrease in temperature may cause the ants to move their nest location. By moving out away from the shade of a vegetation patch and creating more sites for plant establishment, ants of F. pacifica may be effecting the expansion of vegetation patches. Since primary succession at Mount St. Helens is a slow process, the seemingly insignificant effect of ants on this process may be relatively important.

 

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