SELECTION FOR BIOMASS PRODUCTION BASED ON RESPIRATION PARAMETERS IN EUCALYPTS - EFFECTS OF ORIGIN AND GROWTH CLIMATES ON GROWTH-RATES

Seventeen Eucalyptus species and 30 rapid-growing Eucalyptus camaldule nsis trees (referred to as plus trees), growing in a plantation were s tudied to examine relationships among measured plant growth and respir atory parameters, geographical origins, and growth climate. The respir atory parameters measured at two different temperatures by isothermal calorimetry were metabolic heat rate, rate of CO2 production, and the ratio of heat rate to CO2 rate. Metabolic heat rate was also measured as a continuous function of temperature by differential scanning calor imetry in the range of 10 to 40 degrees C. Tree growth was measured as rates of height and stem volume growth. The values of respiratory and growth variables of Eucalyptus species are significantly correlated w ith latitude and altitude of origin of their seed sources. The maximum metabolic heat rate, the temperature of the maximum heat rate, the te mperature coefficients of metabolic rate, and the temperatures at whic h the slopes of Arrhenius plots change are all genetically determined parameters that vary both within and among species. Measurement of gro wth rate - respiration rate - temperature relationships guide understa nding of why relative growth rates of Eucalyptus species and individua l genotypes differ with climate, making it possible to identify genoty pes best suited for rapid growth in different climates. The temperatur e dependence of respiration rates is an important factor determining r elative growth rates of eucalypts in different climates. To achieve op timum biomass production the temperature dependence of individual plan ts must be matched to growth climate.