Post Doctorate: Examination of climatic controls on biomass production, Vancouver Island, British
B.Sc. (Hons) Thesis: Radio-echo sounding Rae Glacier, Front Ranges of the southern Canadian Rocky
Laroque, C.P., 2002. Dendroclimatic Response of High-Elevation Conifers, Vancouver Island, British Columbia. Ph.D. Dissertation, University of Victoria, Victoria, British Columbia, 213p.
The aim of this research program was to examine the growth response of high-elevation conifers on Vancouver Island to past, present and future climates. Forty locations were sampled and 88 chronologies were used to describe radial-growth changes over time and space. Radial-growth trends have been similar across Vancouver Island for most of the past 500 years. Large-scale oceanic influences on climate were shown to be strong forcing mechanisms to radial growth. Master chronologies were constructed for each of the five tree species examined: mountain hemlock, Tsuga mertensiana (Bong.) Carr., yellow-cedar, Chamaecyparis nootkatensis (D. Don) Spach, western hemlock, Tsuga heterophylla (Raf.) Sarg., Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and western red-cedar, Thuja plicata Donn. The responses of these species to climate were combined to develop multiple aggregate chronologies (MACs). The MACs are able to record a stronger relationship to climate than all but the best single-species chronologies, with relationships to seasonalized parameters improved to a greater degree than those of single-month variables.
Using these MAC relationships, proxy information was derived for four climate parameters (April 1 snowpack depth, June-July temperature, July temperature, July precipitation). The explained variance of the models was higher in the two seasonal reconstructions (April 1 snowpack depth r2 = 41 %, June-July temperature r2 = 34 %) than for individual monthly reconstructions (July precipitation r2 = 15 %, July temperature r2 = 24 %). A wavelet analysis showed that each of the four models contains dominant modes of variability throughout time at approximately 16, 32, 65 and 130-150 year periods. Each mode of variability seems to be linked to ocean forcing mechanisms.
Climate/radial-growth relationships were used to predict radial growth under various future climate scenarios. TREE (Tree-ring Radial Expansion Estimator) was developed to present an interactive, internet-based radial-growth model, which calculates the short-term radial-growth response for each tree species to user-defined climate change scenarios. Long-term radial-growth responses were produced using data from general circulation models to develop relationships that predict future radial growth of each tree species. These predictions highlight which species are susceptible to future shifts in climate and indicate which climate parameters may drive changes in radial growth.
Laroque, C.P., 1995. The Dendrochronology and Dendroclimatology of Yellow-cedar on Vancouver Island, British Columbia. M.Sc. Thesis, University of Victoria, Victoria, British Columbia, 104p.
The purpose of this study was to investigate the dendrochronological and dendroclimatological potential of yellow-cedar in the Pacific Northwest of North America. A primary objective was to establish whether the growth response of yellow-cedar is sensitive to climate fluctuations. Once it was determined that yellow-cedar was inherently sensitive, further dendroclimatological investigations were attempted.
Trees were sampled at five sites between latitudes 50? and 51? on Vancouver Island. A total of 380 increment cores were collected in the summer of 1994. The samples were subsequently visually cross-dated, prior to ring-width measurement. Site indices were created and the five sites revealed a strong visual and statistical similarity. A regional index was constructed that represents the oldest living chronology for tree growth in Canada.
A response function analysis was initiated to determine the significant climatic parameters to ring growth. This analysis identified previous August temperature as the variable most likely to influence variation in ring width. This variable was used to estimate current August temperature and associated parameters. The chronologies were compared to other relevant research on Vancouver Island and a common climate signal was apparent.