CLIMATE-GROWTH RATE RELATIONSHIPS IN CONIFERS AMONG SITES WITH SUBSTRATE MEDIATED VEGETATION HISTORIES IN THE KLAMATH MOUNTAIN FORESTS
Open Access
- Author:
- Bernstein, Kevin Daniel
- Graduate Program:
- Geography
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 06, 2016
- Committee Members:
- Alan H Taylor, Thesis Advisor/Co-Advisor
Andrew Mark Carleton, Committee Member
Cynthia Ann Brewer, Committee Member - Keywords:
- Climate Change
Geology
Temperature
Precipitation
Growth
Dendrochronology
Klamath Mountains
Mountain Ecosystems
Forests
Adaptation
Refugia
Ultramafic - Abstract:
- Higher temperatures and increased drought associated with climate change are influencing forest growth globally. Understanding how past climate variation has influenced tree growth in different settings is essential for predicting the spatial patterns of ecosystem responses to climate change. In the sub-alpine forests of the Klamath Mountains, lake sediment pollen cores have documented different tree species compositional responses to climate variability on ultramafic (nutrient poor) and non-ultramafic (nutrient rich) substrates. Non-ultramafic substrates show significant climate-driven vegetation change while ultramafic substrates show relative compositional stability, suggesting that ecosystem responses to climate are strongly mediated by substrate. This research uses dendroclimatology methods to test if substrate mediates the variation of radial growth in response to climate. Growth sensitivity to temperature and precipitation variables-- monthly, seasonal and annual-- is examined. Untangling the effect of substrate conditions on climate-growth rate relationships improves our knowledge of how projected climate change will affect forest composition and growth. Accordingly, this research found that the climate-growth rate relationships were consistent across substrate type. This result suggests that the climate-species performance relationship was not responsible for the differences in vegetation history observed in pollen cores on different substrate types. Differences in species competition on sites may better explain the divergent vegetation histories.