Research About succession

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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Posted On: Filed Under: Biological Research

Dynamic Spatial Patterns During Succession: Resolving Patterns and Mechanisms using Grid-Based Spatial Automata Models

(Project Summary from NSF Research Grant). Our major objective is to investigate how the spatial relationships among individual plants contribute to successional dynamics and influences the spatial patterns that result. We propose to investigate the effects of spatial interactions at the individual level on population dynamics and ecosystem succession on the Pumice Plain near Mount St. Helens, Washington. Spatial analyses of annual field survey data will test the significance of number, size, and species of neighboring plants on growth, survival, and recruitment. Computer models using grid-based spatial automata will implement alternative life histories and individual-level interactions to simulate spatial dynamics during primary succession. The results of this study will provide insights into integration of spatial dynamics across three levels of ecological organization: at the individual level, spatially modified growth rates; at the population level, spatially modified recruitment and mortality; at the ecosystem level, dynamic spatial patterns during succession.

 

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Posted On: Filed Under: Biological Research

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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Posted On: Filed Under: Biological Research

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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Posted On: Filed Under: Biological Research

Patterns and mechanisms of early plant primary succession on the pumice plain.

Primary colonists and mechanisms of their arrival to the pumice plain have been monitored since 1986. Measurements of seed rain have shown that the most common wind dispersed species arriving on the pumice plain are Anaphalis margaritacea, Epilobium angustifolium, and E. watsonii. Of the early colonists A. margaritacea is the most wide spread species, but Lupinus lepidus is the most abundant species. In addition the L. lepidus population is increasing dramatically.

 

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Posted On: Filed Under: Biological Research

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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Posted On: Filed Under: Biological Research

Forested plant association classification

This work, which includes sample sites on the Mount St. Helens National Volcanic Monument, extends across forested areas of the entire Gifford Pinchot National Forest.

 

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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.

 

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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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Demography of Lupinus lepidus on the pumice plain and its role in primary and secondary succession.

This study details the demography of two populations of Lupinus lepidus, a primary successional plant species growing on the Pumice Plain, and also investigates the role lupine plays in the recruitment of additional species through facilitation. Lupine and other plant species’ populations have been censused once or twice each growing season from 1982-1991. Prairie lupine was the first species to colonize the barren deposits of the Pumice Plain and attained extremely high densities in certain portions of our plots during the census years.

 

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