THE DENDROCHRONOLOGICAL CHARACTERISTICS OF ALPINE LARCH

Ring-width chronologies have been developed for alpine larch (Larix lyallii Parl.) at six tree-line sites in the Banff-Kananaskis area of the southern Canadian Rockies. Evaluation of all chronologies confirms that alpine larch ring-width series have higher mean sensitivities, lower autocorrelation, and greater common variance than series from other tree species growing at tree line in this area. Missing and very narrow rings created cross-dating difficulties at all sites but were most problematic for the sites along the Continental Divide. Up to 1% of the rings were missing from entire chronologies, but for specific years, up to 77% of the rings were missing at one site. Marker (narrow) rings were present at all sites for the years 1610, 1654, 1715, 1720, 1723, 1752, 1799, 1824, 1842, 1844, 1915, 1925, 1951, and 1971. Tree growth rates were reduced for the periods 1675-1710, 1815-1850, and 1960-1978 whereas increased growth occurred during 1650-1680, 1750-1800, 1850-1900, and 1920-1950. The only factor that could affect all sites over such a broad geographic area is climate. Principal components analysis indicated that the first eigenvector derived from the six chronologies accounted for 70.7% of their common variance and the first three components accounted for 91.6%. The high correlation between the six first principal component and standard chronologies suggested that either method may be used for standardizing tree-ring data from alpine larch.