Research About animals

Posted On: Filed Under: Biological Research

Effect of herbivores on Sitka willow and associated plant and animal communities and soils.

The invasion of trees and shrubs in early succession is often transformative because of their potential to outcompete early pioneers, provide animal habitat, influence nutrient cycling, and occupy sites over long time spans. The extent to which insect herbivores influence such successional transitions is unknown. We are investigating whether herbivory by a pair of stem-boring insects may substantially impede the structural dominance of Salix sitchensis, the first abundant woody colonist on a large primary successional site at Mount St. Helens volcano, Washington, USA. We also quantify vegetation and soil development at these same sites. Our collaborator Charlie Crisafulli (USFS) quantifies bird use of these sites, eventually allowing us to link herbivore effects on vegetation to bird habitat.

 

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Insect colonization and invasion in the recovering devastation zone of Mount St. Helens.

Vegetation patches at Mount St. Helens represent discrete islands that are a focus for interactions among plants and insects. Our continuing studies focus on the role of biotic interactions (plant-herbivore and predator-prey), dispersal, and disturbance in this highly fragmented landscape. In the 1997 field season, we aim to address two primary questions: 1) What factors have allowed exotic ladybird beetles to displace native ladybird species within the monument? and 2) How does the size of vegetation patches influence colonization by insect species?

 

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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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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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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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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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Reorganization of avian communities at Mount St. Helens

This study was initiated to document the reorganization of bird communities on lands disturbed by the cataclysmic eruption of Mount St Helens. Bird communities were surveyed along a disturbance gradient comprised of four structurally distinct volcanic impact zones and at undisturbed (reference) sites. Forty-two bird species were observed at the eight sites during the survey years. Species richness was inversely related to disturbance intensity. Richness values for the disturbance zones were; Reference (17), Ashfall (16), Blowdown (7) and Pyroclastic (2), respectively. Cluster analyses for community composition and foraging guilds indicate that our sites cluster into 3 groups: 1) sites that were volcanically undisturbed and those that received ashfall; 2) plots that experienced blowdown intensity force; 3) sites that were subjected to blast force intensity. The reorganization of bird communities is largely determined by the post eruptive habitat components available. As vegetation recovery increases across the landscape we expect to see recruitment of additional species and an eventual convergence of bird species composition among the sites.

 

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