E-Thesis 252 views 56 downloads
A 3,000-yr high-resolution reconstruction of forest disturbances in the Cascade Range, Oregon / MATTHEW WATKINS
Swansea University Author: MATTHEW WATKINS
DOI (Published version): 10.23889/SUthesis.60295
Abstract
Current outbreaks of Dendroctonus bark beetles across the Pacific Northwest are widely regarded as unprecedented with the increased scale and severity of such outbreaks attributed to anthropogenic warming over the 19th and 20th Centuries. Despite such severe outbreaks observed in recent years, very...
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Swansea
2022
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Froyd, Cynthia ; Consuegra del Olmo, Sonia ; Woodborne, Stephan ; Johnson, Julie |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa60295 |
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| Abstract: |
Current outbreaks of Dendroctonus bark beetles across the Pacific Northwest are widely regarded as unprecedented with the increased scale and severity of such outbreaks attributed to anthropogenic warming over the 19th and 20th Centuries. Despite such severe outbreaks observed in recent years, very little is known of historic occurrence of these forest pests. Much of the historic reconstructions of forest disturbance in this region are focussed on the Coastal Mountain Range and Willamette Valley, Oregon, and southwestern Washington. This thesis aimed to address important knowledge gaps associated with forest disturbances by producing a high-resolution fire history reconstruction at three sites within the crest of the Cascade Range, Oregon, along with the development of sedaDNA-methodologies for the direct detection of several key forest pests, including the mountain pine beetle (Dendroctonus ponderosae), the Douglas-fir beetle (Dendroctonus pseudotsugae), and the genus of budworm Choristoneura. The fossil charcoal records identified a period of heighted fire activity pre-700 yr BP, attributed to the Medieval Climate Anomaly, followed by a period of suppressed fire activity between 700 yr BP and present, associated with the effects of the Little Ice Age. DNA-based methods revealed the presence of D. pseudotsugae and Choristoneura occidentalis within lake sediments during periods of known outbreaks as inferred by aerial detection survey data. These results increase our understanding of fire dynamics within the Pacific Northwest and further emphasise the potential role of DNA-based methods in the field of palaeoecology. |
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| Item Description: |
ORCiD identifier: https://orcid.org/0000-0001-8576-6504 |
| Keywords: |
Palaeoecology, sedaDNA, Forest disturbance, Bark beetles, Dendroctonus, Fire history |
| College: |
Faculty of Science and Engineering |