An investigation of the snowpack signal in moisture-sensitive trees from the Southern Canadian Cordillera

Variations in mountain snowpack in the western Canadian Cordillera have widespread and important impacts on ecosystems, environmental processes and socio-economic activities (e.g. water availability downstream). Historical records of snowpack generally span only the latter half of the 20th century offering a limited perspective on the causes and uniqueness of recently observed changes across the region. This paper explores the potential utility of a network of low elevation Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) tree ring-width chronologies to reconstruct past snowpack variations. Correlation coefficients between the tree-ring chronologies and a set of snow water equivalent (SWE) records are calculated and mapped. Separate analyses were carried out for total ring- width (TRW) and partial-ring measurements (earlywood and latewood; EW and LW). A set of Adjusted LW chronologies was also developed; in these, the relationship between LW and the preceding EW width has been removed. The ring-width chronologies exhibit moderately strong relationships with SWE records from the western Canadian Cordillera and these relationships vary in sign across the region. Distinctive regional groups are identified where chronologies exhibit same-sign correlations with SWE, in possible accordance with the elevation and characteristics of the tree-ring chronology sample sites. The EW chronologies correlate more strongly and consistently with SWE records in regions where the growth relationship with SWE is negative. The LW chronologies, and particularly the Adjusted LW chronologies, exhibit a greater number of positive correlations with the set of SWE records. Collectively these results offer valuable insights for developing a targeted sampling and/or reconstruction strategy that can exploit these different relationships with SWE to generate more robust estimates of pre-instrumental snowpack for the region.