Effects of climate on growth traits of river red gum are determined by respiration parameters

Temperature is the major uncontrollable climate variable in plantation fore stry. Matching plants to climate is essential for optimizing growth. Matchi ng is usually done with field trials because of the lack of a predictive re lation between laboratory measurements of physiological responses and clima tic factors affecting growth. This paper evaluates the potential of using r espiration parameters for selection of appropriate drainage or seed sources within a drainage for superior growth in a particular climate. The growth traits measured are tree height, stem diameter and stem volume. The respira tory parameters measured are respiratory heat rate, rate of CO2 production, and temperature dependence of respiratory heat rate. Five open-pollinated families from each of nine seed sources of river red gum (Eucalyptus camald ulensis Dehnh.) were studied following selection from a larger set of seed sources planted at three plantations in California. The three plantations d iffer in climate, particularly in extreme temperatures, diurnal temperature variability and total rainfall. Within each plantation, growth and respira tion parameters show high genetic variation [overall coefficient of variati on (CV) = 14-58%, family CV = 11-33%], with at least one of these traits sh owing significant (P < 0.10) difference due to drainage, or source within d rainage, or families within source. The relationship of growth to respirati on for each trait differs, depending on test plantation, origin drainage, s ource or family, suggesting a unique pattern for each trait. Correlation of drainage level averages between growth and respiration were strongly negat ive and significant (P = 0.10-0.01). Rankings for drainages between paired plantations were strong and significant (P = 0.10-0.05) only for respiratio n, but not for growth traits.