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https://ir.library.oregonstate.edu/concern/undergraduate_thesis_or_projects/v118rg498

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  • This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches of the McKenzie River watershed of the Oregon Cascade Mountains. We tested the use of Δ¹³C values from latewood, corroborated by tree-ring width chronologies as precipitation proxies to develop correlations between moisture stress and climate variables. Tree species at each site included Douglas-fir and mountain hemlock. Interpolated meteorological and snowpack data included snow water equivalent (SWE), precipitation, atmospheric temperature, vapor pressure deficit (VPD), relative humidity (RH), and a metric estimating growing season length. Significant correlations between latewood Δ¹³C and winter SWE at each site indicated the importance of winter snowpack to our selected tree species (r = 0.35, r = 0.43). Late summer precipitation and relative humidity (RH) were also significantly correlated with Δ¹³C (r = 0.49, r = 0.46; r = 0.43, r = 0.44). High correlations at both sites reinforced that late summer VPD was the primary driver of Δ¹³C (r = - 0.67, r = -0.61), which is often associated with moisture stress. This was further supported by correlations between air temperature and Δ¹³C (r = -0.46, r = -0.47), which drives much of the variation in VPD. Growing season length also showed significance in mountain hemlocks at the site with longer average snowpack (r = -0.22, r = -0.44). Moisture supplied by spring snow melt is a seasonably limited resource, nonetheless both sites clearly showed that snowpack acts as a valuable moisture subsidy to coniferous mountain forests in the Oregon Cascades. This study acts as a useful case study for future investigations into the relationship between snowpack and forest health in the Pacific North West.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2016-01-07T18:56:50Z (GMT) No. of bitstreams: 2 Ratcliff_Thesis.pdf: 1590808 bytes, checksum: 586372469fd540d5e3ae3f11a27e3f97 (MD5) Ratclif Thesis Seminar.pptx: 40364147 bytes, checksum: 9eece3b5a785b6c6edbd99e9be19f3b7 (MD5)
  • description.provenance : Made available in DSpace on 2016-01-07T18:56:50Z (GMT). No. of bitstreams: 2 Ratcliff_Thesis.pdf: 1590808 bytes, checksum: 586372469fd540d5e3ae3f11a27e3f97 (MD5) Ratclif Thesis Seminar.pptx: 40364147 bytes, checksum: 9eece3b5a785b6c6edbd99e9be19f3b7 (MD5)
  • description.provenance : Submitted by Wanda Crannell (brr@oregonstate.edu) on 2016-01-01T22:59:35Z No. of bitstreams: 2 Ratcliff_Thesis.pdf: 1590808 bytes, checksum: 586372469fd540d5e3ae3f11a27e3f97 (MD5) Ratclif Thesis Seminar.pptx: 40364147 bytes, checksum: 9eece3b5a785b6c6edbd99e9be19f3b7 (MD5)

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