Biological Research

Posted On: Filed Under: Biological Research

Small mammal recolonization on the Mount St. Helens volcano

The purpose of this study was to systematically document the initial survival and the subsequent recolonization of small mammal species into disturbed regions of Mount St. Helens, and to ascertain differences in early successional patterns among various habitat types and levels of disturbance. Trapping efforts have documented the recolonization of small mammals {Rodentia, Insectivora, Lagomorpha and Carnivora (Mustelidae)} into representative sites of four broadly defined montane habitats (forests, clearcuts, subalpine meadows and riparian ravines) that were subjected to increasing degrees of volcanic disturbance (undisturbed, ashfall, mud flow, tree blowdown, and pyroclastic/debris flow).

 

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Posted On: Filed Under: Biological Research

The herpetofauna of Mount St. Helens: survival and colonization following the 1980 eruption.

This study documents the survival and colonization of reptiles and amphibians in areas impacted by the 1980 eruption of Mount St. Helens. Surveys were conducted at 15 locations, with representative sites in three distinct volcanic impact zones, 1) ashfall, 2) blowdown, and 3) blast, during spring and summer from 1980 through 1991. Twelve species of herptiles (9 amphibians, 3 reptiles) are considered to have survived volcanic influences ranging from the directed blast to the accumulation of ash in otherwise unaltered habitats. These survivors represent most of a hypothetical list of 16 species considered to have occurred in the area before the eruption. Generally, surviving species were characterized by being more aquatic than those not found and this was attributed to the thermal buffering capacity of cool ice and snow covered aquatic systems where individuals were protected from the hot volcanic gases.

 

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Posted On: Filed Under: Biological Research

Blast zone lakes and organic geochemistry

The objective of the research is to describe the processes controlling dissolved organic material in the lake water following the 1980 eruption of Mt. St. Helens. The concentrations of DOC (dissolved organic carbon) increased 50-fold after the eruption and these increases influenced the chemistry and biology of the lakes for several years. We have shown that most of this DOC was comprised of organic acids classified as either fulvic or hydrophilic acids, similar to those in typical natural waters. We found that between 1980 and 1983, these organic acid fractions underwent oxidative changes in their chemical characteristics. Similar changes may occur in more typical lakes.

 

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Recovery of riparian vegetation at Mount St. Helens

This study documents rates and patterns of vegetation recovery at lakes and streams in the blast zone of the May 1980 eruption. Recovery of streamside vegetation was dominated by plants that resprouted from below ground parts that survived the blast. Depending upon frequencies and intensity of secondary disturbances, revegetation from seeds has become increasingly important. Flooding, battering, and deposition of reworked tephra have extremely important effects on streamside revegetation. Recovery rates are more rapid at greater distances from the volcano where blast effects were less devastating.

 

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Stream channel adjustments in the Smith – Muddy River drainage after the 1980 Mount St. Helens eruptions

Stream channel response to the 1980 eruption of Mount St. Helens has varied widely. Stream channels that received only airfall deposits have shown no significant sedimentation following the eruption. In drainage basins that received both blast and airfall deposits, localized channel modification has been observed. However, as the blast/airfall deposits are predominately sand-sized, they have been quickly removed from the steep low-order channels surrounding the mountain with little net effect on pre-eruption channel morphology. Some subsequent channel modification has resulted in lowered gradient reaches downstream as sediment eroded from upstream hill slopes and stream channels has been redeposited in these reaches. Long-term effects in blast/airfall affected streams appear limited to channels subjected to debris torrents resulting from shallow-seated landsliding and breakup of in-channel debris jams.

 

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Microbiology of thermal vents

Our objectives are to observe, enrich, isolate, and identify bacteria from hot springs in the Mount St. Helens area. If any previously undescribed isolates are found, we will characterize them. In two trips to the area so far, we have observed the following: Cyanobacterial (blue-green algal) mats containing filamentous forms, some with heterocysts; filaments with the appearance of the sulfur oxidizer Beggiatoa or Thiothrix; and numerous rod shaped and coccus shaped bacteria. From anoxic sediment at 60oC, we obtained an enrichment of methanogenic bacteria that appeared similar to Methanobacterium thermoautotrophicum. We also obtained an enrichment of the green non-sulfur photosynthetic bacterium, Chloroflexus. We observed few organisms in a vent at 85oC.

 

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Post eruption studies of ecological recovery of lakes and rivers in the blast zone of Mount St. Helens

This study concentrates on the effects of the May 1980 eruption on Spirit Lake. During and subsequent to the eruption, Spirit Lake received debris avalanche material, timber and other forest vegetation, pyroclastic flows, mudflows, ashfall, and geothermal waters.

 

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Posted On: Filed Under: Biological Research

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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Ecological factors determining population size of Aphis varians.

Research is intended to assess the ecological factor(s) of greatest importance in determining the population size of an aphid (Aphis varians) feeding on fireweed (Epilobium angustifolium). We manipulated the host plant (by shading, watering, and fertilizing), the size of fireweed patches, the density of a leaf-feeding beetle (Altica tombacina) which also utilizes fireweed, and the presence of predators of the aphid (primarily ladybird beetles and syrphid flies) by means of cages.

 

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Effects of airfall tephra on forests northeast of Mount St. Helens

The May 18th, 1980 eruption of Mount St. Helens deposited tephra over a very large area of forest land in Southwest Washington. Tephra affected forest stands primarily by covering the foliage. Most tephra originally deposited is now on the forest floor; however, much of the finest deposits were retained by the foliage and still persist in the crowns of many trees.

 

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