Research About invertebrate

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.

 

View full abstract (77A)

Tags: , , , ,

Posted On: Filed Under: Biological Research

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.

 

View the full abstract (61A)

Tags: , , , ,

Posted On: Filed Under: Biological Research

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.

 

View the full abstract (58A)

Tags: , , , , ,

Posted On: Filed Under: Biological Research

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.

 

View the full abstract (39A)

Tags: , ,

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.

 

View the full abstract (35A)

Tags: , , , , , , ,

Posted On: Filed Under: Biological Research

Spider biogeography at Mount St. Helens

Spider populations on the pumice plain were sampled and compared to those at a control site on the south slope of Mount St. Helens that received only tephra from the May 1980 eruption. All living organisms were either swept away or buried by the eruption at the pumice plain study site; there were no survivors and vegetation was sparse at this location during the years of sampling. Sampling at the control site revealed no significant effects on the spider community. The number of individuals trapped at both sites was nearly the same, but many more species were trapped on the pumice plain than at the control site. The majority of species arriving on the pumice plain are wind dispersed. They appear to be coming from lowlands approximately twenty miles to the west, transported by prevailing winds through the corridor of the Toutle River Valley. Most spiders perish soon after their arrival, and as of 1985, spiders were not colonizing this location.

 

View the full abstract (15A)

Tags: , , ,

Posted On: Filed Under: Biological Research

Recovery of aquatic insect communities in streams near Mount St. Helens

We have monitored stream insect communities from 1980 to 1988 in Clearwater Creek, Elk Creek, and Ape Canyon. Quantitative and qualitative samples indicate rapid colonization in 1981-82, and then a gradual increase in richness and diversity. Over 200 taxa have now been collected from Ape or Clearwater Creeks.

 

View the full abstract (7A)

Tags: , , , , ,

Posted On: Filed Under: Biological Research

Population ecology of the aphid Aphthargelia symphoricarpi on Mount St. Helens

I have examined the ecology of the aphid Aphthargelia symphoricarpi in terms of its interactions with its host plant Polygonum newberryi and its major predator, the ant Formica fusca. My approach involves a combination of field experimentation and observation with mathematical modelling.

 

View the full abstract (5A)

Tags: , , , , ,

Posted On: Filed Under: Biological Research

Arthropod recolonization of Mount St. Helens.

Ashfall and blast zone sites have been sampled in order to monitor the recovery of insect and spider populations reduced by the May 1980 eruption. There were many survivors of the eruption in ashfall sites, especially of sedentary species and others that were protected in micro-refugia. Mortality in arthropod populations was correlated with the depth of the ashfall. Using ant colonies as an index, areas with 15 cm or less of ash deposited had species numbers similar to sites outside the devastated area. However in all areas arthropod populations have remained low compared to arthropod population recovery following clearcutting.

 

View the full abstract (24A)

Tags: , , , , ,