Competitive dynamics in a mixed garry oak/douglas-fir stand based on tree ring analysis
At many North American sites, Garry oak associated ecosystems are being encroached upon by Douglas-fir; and Garry oak trees are not regenerating. This thesis investigates effects of competition between Garry oak and Douglas-fir on annual ring-width growth. Effects of stand structure and composition on climate-growth relationships were tested. Significant differences in radial growth sensitivity to precipitation and temperature were found between Garry oak and Douglas-fir. Stand composition and structure were found to affect radial growth sensitivity to limiting factors, especially in Garry oak trees, where density, tree age, tree morphology and stand composition significantly affected radial growth/climate relationships. These findings challenge the implication that tree-growth/climate relationships are stable over time in dendroclimatology and may affect the accuracy of climate reconstructions. The results of this study indicate stress on the radial-growth of Gaily oak from competition with Douglas-fir which supports need for management of Garry oak associated ecosystems.