Natural and Anthropogenic Influences on the Holocene Fire and Vegetation History of the Willamette Valley, Northwest Oregon and Southwest Washington

Simple item page
dc.contributor.authorWalsh, Megan Kathleen, 1976-
dc.date.accessioned2009-07-23T00:16:45Z
dc.date.available2009-07-23T00:16:45Z
dc.date.issued2008-12
dc.descriptionxvii, 382 p. : ill. (some col.), maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.en_US
dc.description.abstractThe debate concerning the role of natural versus anthropogenic burning in shaping the prehistoric vegetation patterns of the Willamette Valley of Oregon and Washington remains highly contentious. To address this, pollen and high-resolution charcoal records obtained from lake sediments were analyzed to reconstruct the Holocene fire and vegetation history, in order to assess the relative influence of climate variability and anthropogenic activity on those histories. Two sites provided information on the last 11,000 years. At one site at the northern margin of the Willamette Valley, shifts in fire activity and vegetation compared closely with millennial- and centennial-time scale variations in climate, and there was no evidence that anthropogenic burning affected the natural fire-climate linkages prior to Euro-American arrival. In contrast, the fire and vegetation history at a site in the central Willamette Valley showed relatively little vegetation change in response to both millennial- and centennial-scale climate variability, but fire activity varied widely in both frequency and severity. A comparison of this paleoecological reconstruction with archaeological evidence suggests that anthropogenic burning near the site may have influenced middle- to late-Holocene fire regimes. The fire history of the last 1200 years was compared at five sites along a north-south transect through the Willamette Valley. Forested upland sites showed stronger fire-climate linkages and little human influence, whereas lowland sites located in former prairie and savanna showed temporal patterns in fire activity that suggest a significant human impact. A decline in fire activity at several sites in the last 600 years was attributed to the effects of a cooling climate as well as the decline of Native American populations. The impacts of Euro-American settlement on the records include dramatic shifts in vegetation assemblages and large fire events associated with land clearance. The results of this research contribute to our understanding of long-term vegetation dynamics and the role of fire, both natural- and human-ignited, in shaping ecosystems, as well as provide an historical context for evaluating recent shifts in plant communities in the Willamette Valley.en_US
dc.description.sponsorshipAdvisers: Cathy Whitlock, Patrick J. Bartleinen_US
dc.identifier.urihttps://hdl.handle.net/1794/9488
dc.language.isoen_USen_US
dc.publisherUniversity of Oregonen_US
dc.relation.ispartofseriesUniversity of Oregon theses, Dept. of Geography, Ph. D., 2008;
dc.subjectAnthropogenic influencesen_US
dc.subjectVegetationen_US
dc.subjectFire historyen_US
dc.subjectWillamette River Valley (Or.)en_US
dc.subjectCharcoalen_US
dc.subjectPhysical geographyen_US
dc.subjectNative American studiesen_US
dc.subjectEnvironmental scienceen_US
dc.subjectPlants -- Effect of human beings on -- Oregon -- Willamette River Valley
dc.subjectPlants -- Effect of human beings on -- Oregon, Western
dc.subjectPlants -- Effect of human beings on -- Washington (State), Western
dc.titleNatural and Anthropogenic Influences on the Holocene Fire and Vegetation History of the Willamette Valley, Northwest Oregon and Southwest Washingtonen_US
dc.typeThesisen_US

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Walsh_Megan_Kathleen_PhD_Fall08.pdf
Size:
3.79 MB
Format:
Adobe Portable Document Format
Description:
thesis
Download
License bundle
Now showing 1 - 2 of 2
Name:
license.txt
Size:
2.21 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Name:
Walsh_Megan_08Fall_Phd.pdf
Size:
26.32 KB
Format:
Adobe Portable Document Format
Description:
permission form
Download

Collections

Theses and Dissertations
Geography Theses and Dissertations