Picea (spruce) growth rate (mm year−1) changes in southwest Yukon (Canada) since the mid 19th century

Abstract

Analyses of maximum early tree ring growth within a regional curve standardization (RCS) framework were used to construct ring width chronologies in mm year−1 to estimate historical growth rates in southwest Yukon (Canada), without the necessity of correcting for age related changes. The analysis relied on the use of the 11th–50th year growth rings to standardize chronology comparisons. This age range represents the period of peak radial growth for Picea albertiana and P. glauca (white spruces), which are common trees on upland boreal sites in the study area. Of 1,460 available Picea ring series, 1,029 fit the criteria for inclusion in the study and they represented five commonly occurring RCS curve types. When converted to chronologies, all curve types had year-to-year fluctuations in average ring widths (RW11–50), but nine of the 12 RCS types (four types in three study areas) also had long-term growth rate increases of 15–132% between ad 1850 and 2000, based on regression modeling (R/r = 0.54–0.76, p 0.94, n > 100) with conventional tree ring width index values derived from multiple RCS curves. This indicates that the two chronology construction approaches have very similar temporal patterns despite the maximum early growth analysis technique representing ring widths in mm.