Biological Research

Posted On: Filed Under: Biological Research

Survival and growth of native plant species planted in the Mount St. Helens blast area.

The principal objective of this research was to determine the potential of establishing vegetative cover in areas with deep deposits of volcanic materials from the eruptions of Mount St. Helens in 1980 in order to provide for erosion control. Three sites northeast and northwest of the mountain that received approximately 25 cm or more of volcanic materials were studied: two with largely pumice materials and one with predominately fine ash.

 

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Posted On: Filed Under: Biological Research

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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Posted On: Filed Under: Biological Research

Surface modification of Muddy River lahar deposit, Mount St. Helens National Volcanic Monument, Skamania County, Washington

Purpose of the project is to note and describe the extent of modification, since 1980, of the surface of the upper Muddy River lahar deposit. Several traverses will involve measurements concerning the density, width, and depth of drainage channels, and changes to interfluve areas. These will be compared with features recorded on aerial photographs and related to longitudinal gradients of channels and surface. The information is to be summarized in a written report.

 

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Contributions by lupines to volcanic soils.

The effects of colonization of Lupinus lepidus and L. latifolius on carbon, nitrogen, and microbial activity in volcanically disturbed soils was investigated in several studies. Examination of nitrogen fixation rates showed that both species have diurnal and seasonal fluctuations that appear to be associated with environmental factors. Nitrogen fixation rates are highest during daylight and early in the growing season, and the seasonal pattern is reflected in carbon and nitrogen levels; that is, as nitrogen fixation increases, carbon and nitrogen production increases. First year plants of both species fix similar amounts of nitrogen.

 

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Posted On: Filed Under: Biological Research

Effects of eruptions and post-eruptive phenomena on caves and pseudokarst of Mount St. Helens

Beginning June 1980 systematic observations and measurements are documenting the effects of the eruption and post-eruptive events on the caves and pseudokarst of Mount St. Helens. Caves of the Cave Basalt Lava Flow were essentially free of physical impacts by the eruptions, but the biota of some was severely impacted by ashfall. Depending on the local physical geography, some of the caves were severely impacted by post-eruption mudflows.

 

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Investigation of the effects of Mount St. Helens tephra on soil gas composition and subsequent effects on root and mycorrhizal growth of Abies amabilis

It was hypothesized that tephra from the May 1980 eruption of Mount St. Helens would form an impervious layer, limiting gas exchange (oxygen and carbon dioxide) in the soil. Resulting limited oxygen and excessive carbon dioxide were predicted to affect root and mycorrhizal growth of Pacific silver fir (Abies amabilis) causing higher than normal foliage loss.

 

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Posted On: Filed Under: Biological Research

Long-term succession in subalpine habitats

A long-term study of recovery and primary plant succession in higher elevations was initiated in 1980. The objectives included to document recovery and invasion in several distinct habitats (e.g. lahars, pumice, blasted ridges, tephra) and to determine the mechanisms of invasion and establishment. In addition, large grids of contiguous 100 m2 quadrats have been established since 1986 in several habitats.
Recovery patterns vary with the size and intensity of the initial impacts. Tephra impacted sites were completely recovered by 1983 and subsequent vegetation change has not been directional. In contrast, intensively impacted sites have recovered much more slowly. Recovery rates differ primarily with the degree of isolation, but the intensity of the impact also governs the recovery rate. For example, lahars surrounded by intact vegetation have acquired as many species as intact vegetation, but community structure remains very different. Total cover after 11 growing seasons remains less than 10% of intact vegetation. Nutrients limit the development of biomass and cover, but most species in the immediate vicinity have established on lahars.

 

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Posted On: Filed Under: Biological Research

Plant recovery on the debris avalanche Key Words:

Seed dispersal and plant establishment have been monitored since 1980 on the debris avalanche created by the eruption of Mount St. Helens. The number of plants on the deposit increased over time to a high of almost 2 plants per square meter by 1983. The number of species per 250 meter square plot have increased to a mean of 10.3 in 1983 with 76 species being present over the entire deposit. Four years after the eruption only 30 percent of the species present before the eruption had reestablished themselves, and average plant cover was less than 1 percent. By 1989, plant cover had reached 18 percent.

 

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Posted On: Filed Under: Biological Research

Lakes and thermal environments in the blast zone of Mount St. Helens

Approximately 20 lakes exist in the blast zone of Mount St. Helens. The degree to which they were disturbed on May 18, 1980 ranges from slight to a complete physical, chemical, and biological restructuring. Initially, our research focused on the physical, chemical, and microbial conditions within the lakes. Heavily devastated lakes were markedly changed chemically and all plants and animals eliminated. Recovery took the form of dramatic physical and chemical changes within the lakes which were linked to microbial activity. Rapid recovery occurred the first two years. Once the physical and chemical conditions were ameliorated, further biological succession was possible. Presently, we continue to track these changes.

 

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Distribution of plant detritus and recovery of plants in deposits of May, 1980 eruption of Mount St. Helens

This study seeks to identify types and sizes of plant material and distance and means of deposition in the May 1980 blast of Mount St. Helens. Types of plant material included pieces of moss, leaves, stems, roots, tree branches and trunks. Four types of transport were identified. The debris avalanche deposited plant material 23 km away. Mudflows (lahars) carried material 75 km to the Columbia River. The pressure blast removed vegetation in a 500 km2 area. Pyroclastic flows in conjunction with the plinian column spread plant debris for at least 75 km in a 110o arc to the north and east. These results are being compared with fossilized records of volcanic eruptions worldwide but especially those from Tertiary western United States.

 

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