Research About ashfall zone

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Development of vegetation on barren and high elevation sites.

This study is a continuation of work begun in 1980. Current studies include monitoring permanent plots, monitoring grids, studying relict plots, assessing vegetation in potholes, and describing vegetation along transects. The plots studied to date can be divided into those that are fully recovered, those undergoing secondary succession and those undergoing primary succession. The rate of recovery, measured by the number of species and their cover, is related to proximity to sources of colonists and to habitat stress. The species composition of sites undergoing primary succession is related to proximity to intact vegetation and is strongly affected by distance and by chance effects. Previous studies have demonstrated that environmental factors only weakly predict species composition.

 

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Mechanisms of vegetation change following burial by volcanic tephra

This project continues detailed study of forest understory vegetation change after burial by tephra from Mount St. Helens in 1980. Objectives are to provide a detailed record of pathways of change; to record spatial and temporal variation in soil properties; to determine species characteristics important for recovery from burial; and to use these data to determine the mechanisms of succession. Data will be analyzed to compare responses of different growth forms, species and communities in different conditions of tephra depth, seral age, and time of tephra removal. This study will provide a long-term set of consistent, detailed data about vegetation recovery from an important, widespread disturbance.

 

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Tree ring dating of prehistoric eruptions of Mount St. Helens

This study includes two topics: 1. Dating of prehistoric eruptions of Mount St. Helens using tree ring patterns of living trees and of dead, buried trees. Using increment cores of Douglas fir (Pseudotsuga menziesii), three prehistoric eruptions were dated at 1480, 1482, and 1800 A.D.   View the full abstract (69A)

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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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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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Soil nitrogen along a disturbance gradient.

Soils were studied along a disturbance gradient: Pumice Plain, Timberline parking lot, Harmony, Bismark Mtn., Elk Pass, and Fossil Creek Ridge. N03, NH4, N, P, K, Ca, Mg, C were assayed. NO3 and NH4 were also analyzed from resin bags buried at 15 and 30 cm. Soil samples were collected in 1985. Resin bags were buried for 1 year: 1985 – 86, and 1986 -87.

 

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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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Community reassembly following volcanic disturbance: the ground dwelling beetles (Coleoptera)

This study documents the recovery of beetles within the volcanically disturbed areas of Mount St. Helens and should provide an index to the rate and stage of ecosystem recovery at various points in time since the eruption. Beetles are ideal for monitoring ecological recovery following disturbance as they represent a broad trophic array. The ground dwelling beetle fauna of forests and clearcut habitats were sampled using pitfall traps (10 traps/site) that were open from the time of spring snow melt to early autumn from 1982-1984 and again in 1987 and 1990. Sites sampled include undisturbed “reference” areas and three post-eruption habitats (ashfall, blowdown, and pyroclastic/debris flow).

 

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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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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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