Lichens are an important part of the biota in western Oregon forests, where
they perform valuable ecological roles and contribute significantly to biodiversity.
Lichens in western Oregon are threatened by a number of factors including air
pollution and land use practices. If we wish to maintain the persistence of lichens in
future landscapes it is critical that we understand the responses of lichen communities
and individual lichen species to the environment and forest structure. This dissertation
explores factors that are related to differences in lichen community composition and
the distributions of individual lichen species in the western Cascades of Oregon, using
a large landscape scale data set. I sought to relate major gradients in lichen
community composition to environmental factors, and describe differences in lichen
communities with respect to forest age (Chapter 2). I found three major gradients in
lichen communities at a landscape scale in the western Oregon Cascades. These
gradients were related to climate as expressed by elevation and annual temperature, air
quality, north-south position, the richness of epiphytic macrolichens, and forest age. I developed a rarity score, which can be used to identify hotspots of rare species
diversity at a landscape scale (Chapter 3). I then built descriptive models of this rarity
score to identify abiotic and biotic factors associated with the occurrence of rarity
hotspots. I found that models of rarity score that used explanatory variables based on
lichen community composition performed better than models that used explanatory
variables based solely on environmental factors. I narrowed my focus to the level of
individual species responses to the environment and forest structure by developing
habitat models for 11 lichen species in the western Cascades (Chapter 4). We selected
these species because they performed important ecological roles, were rare across the
landscape and associated with old growth forests, or because their distributions were
poorly understood. These models can be used to increase the efficiency of landscape
level surveys for rare species, predict the response of these species to forest
management practices, and understand factors associated with the distributions of
these lichens. / Graduation date: 2006
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/21005 |
| Date | 30 June 2005 |
| Creators | Martin, Erin P. |
| Contributors | McCune, Bruce P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Relation | Oregon Explorer |
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