Ph.D. Dissertation Abstract by Gregory John Ettl (1995)

Growth response of subalpine fir (Abies lasiocarpa) to climate was studied across its local geographic and elevation range in the Olympic Mountains, Washington. Climate-growth relationships were explored to assess relationships among site chronologies and climatic variables. Radial growth is negatively correlated with winter precipitation at high elevation and wet sites, but not at low and middle elevation dry sites. Growth is positively correlated with current growing season temperature at all sites; however growth is negatively correlated with previous year August temperature, indicating that climate affects growth in subsequent years. Positive correlations between growth and summer precipitation during the growing season at low and middle elevation dry sites suggest that soil moisture is partially limiting to growth on these sites.

Correlation analysis is also used to describe individual growth-climate relationships. Growth response is quantified in years with unusually warmer, colder, wetter, and drier climates during the period 1895-1990. Combinations of climatic variables that result in unusually fast or slow growth years are also described. Differences in growth-climate relationships both among sites, and among individuals from the same site, emphasize within-species variability in response to climate. Growth was not significantly faster or slower on the majority of sites for extreme climate years examined.

Growth response to genetic variability is also examined. Observed heterozygosity ranges from 0.070 to 0.139 for subalpine fir in the Olympics, and 96.9% of the observed genetic variation is within populations. No relationship between multi-locus heterozygosity and growth were observed, but differences in growth were found for specific isozymes. Individuals heterozygous for the loci MDH-l and SIX are negatively associated with growth, while heterozygous individuals for PER, PGI-2, and PGM are positively associated with growth at some elevations. Considerable variation in subalpine fir’s growth response to climate suggest a uniform response to climate change is unlikely. Individual differences in growth-climate relationships probably result from microsite variation (soil depth, soil moisture, wind, insolation) and from individual genetic differences.