| Summary: | The relationship between climate and tree ring chronologies has been considered mainly in relation to temporal variations in the climate regime, and has mainly focused on trees on moisture-stressed sites and/or at the edge of their range. In this thesis, I examined whether temporal patterns in tree ring chronologies within and between three western North American tree species, all growing on zonal (mesic) sites, were consistent across an elevational gradient, and the degree to which ring width variations reflected estimates of past variations in temperature and precipitation. Increment cores were taken from hybrid spruce (Picea glauca x engelmannii), lodgepole pine (Pinus contorta) and Douglas-fir (Pseudotsuga menziesii) along an elevational gradient spanning three biogeoclimatic (BEC) zones (Engelmann Spruce - Subalpine Fir, Montane Spruce, and Interior Douglas-fir zones) in southern interior British Columbia, Canada. Ring width chronologies were prepared and then compared with estimates of past climatic regimes using the climate extrapolation model MTCLIM to create elevational sequences of past temperature and precipitation conditions based on extrapolation from low elevation climate stations. These extrapolations were tested against data from high elevation climate stations in the same general area. Results from correlation, regression and principal component analysis suggest that tree growth/climate relationships over time in these three species were consistent, but that the strength of the response within a species differed by BEC zone. Results indicated that the response to climate was species-dependent, with the strongest response in Douglas-fir and the weakest in hybrid spruce. Finally, a simple computer model was constructed and used to simulate the net primary production for each tree species in relation to recorded climate. Results from this simple modelling exercise explained only a small part of the inter-annual variability of tree-ring growth, but indicated the possibility of successfully simulating the influence of climate on tree growth, provided the submodel is successfully linked to a more complex modelling framework. Results from this thesis will be used to modify an existing ecosystem-level model (FORECAST) to provide it with the capability to simulate climate change effects on tree growth.
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