Author : Jarrett, P. Date : 2008. Title : A dendroclimatic investigation of moisture variability and drought in the Greater Victoria Water Supply Area, Vancouver Island, British Columbia. Publication : Unpublished MSc thesis. University of Victoria, Victoria, British Columbia. Issue : Page(s) : 108 p.
A 616-year Douglas-fir (Pseudotsuga menziesii) chronology was developed to examine the history of drought and moisture variability in the Sooke Watershed, near Victoria, British Columbia. Ring-width chronologies were compared to historical precipitation, air temperature and drought variables (Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI)) to determine the climate/radial-growth response to moisture stress on the sampled stands. Correlations between the ring-width chronologies and climate variables revealed that summer (May to July) precipitation, summer (May-June) SPI and July PDSI were significant limiting factors to radial-width growth. A transfer function was established for each of these variables to create a proxy climate reconstruction of drought in the watershed. The summer precipitation model provided the most accurate representation of past moisture (R2 = 0.20) and demonstrates a history of moisture variability in the watershed. This indicates that cyclical patterns of various scales are controlling patterns of moisture availability in the watershed.