The diverse lichen flora of the Pacific Northwest is being impacted by
population growth and by forest management practices. Accumulating information
about our lichen flora will improve our conservation strategies. This dissertation first
collects information to improve our understanding of how lichen communities vary
among forests of differing structure, and across the western Oregon landscape. It then
proposes a method to predict species occurrence in unsampled sites by utilizing the
information on forest characters and environmental gradients at sampled sites.
Macrolichen communities sampled in coniferous forests revealed that old-growth
stands (>200 yrs old) harbored communities that differed from those in young
forests (50-110 yrs old). Even more atypical communities occurred in macrolichen
hotspots, which were primarily in riparian zones. Many macrolichen species were
associated with these hotspots, including numerous nitrogen-fixing cyanolichens.
Macrolichen species associated with old-growth forested plots included the nitrogen-fixing
lichen Lobaria oregana and several forage-providing alectorioid lichens. The
presence of remnant old trees apparently increased the occurrence of old-growth
associates in young stands. The calicioids, a group of microlichens investigated only in
the Cascades, had a strong association with old growth forest and remnant trees.
Diversity of calicioids may also be increased by legacy structures such as old snags and
wolf trees. These structures increase continuity between current and previous stands.
Macrolichen communities varied between the Coast and Cascade Mountain
Ranges, following climatic gradients, particularly annual precipitation. Successional
patterns in macrolichen communities appeared to differ between the mountain ranges.
The modeling method proposed for using habitat associations to predict
occurrence has several advantages over common modeling methods, such as regression.
The method is simple, avoids parametric assumptions, provides easy updating of
models as additional sites are sampled, and automatically accounts for interactions
among predictor variables. It can be linked with GIS data and software to map
estimated probability of occurrence across landscapes. The data on calicioids from the
Cascades, supplemented with additional stand inventories, were used to test and
demonstrate the modeling method. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32593 |
| Date | 24 May 2000 |
| Creators | Peterson, Eric B. |
| Contributors | McCune, Bruce P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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