MODELLING GROWTH AND ECOPHYSIOLOGICAL RESPONSES OF <em>EUCALYPTUS</em> <em>GRANDIS</em> CLONES IN MINAS GERAIS, BRAZIL

Abstract

The relationships between environment, physiology and dry matter production were studied in rooted cuttings of 11 Eucalyptus grandis (W. Hill ex Maiden) clones after three months growth in the field in Minas Gerais, Brazil. A matrix of Spearman's rank correlation coefficients indicated that stomatal conductance was negatively correlated with leaf area and stem dry weight (r = -0.68 and r = -0.66 respectively, p < 0.05)). Stomatal conductance was also negatively correlated with leaf-, aboveground-, and total dry mass, (r = - 0.55 to r = - 0.59, p< 0.1). Because of their lower stomatal conductance, more vigorous clones were no more water stressed than slower growing clones, despite their greater leaf area. Surface response curves showed that during the dry period of the year, air temperature and relative humidity were the main environmental variables controlling stomatal conductance. These two variables accounted for almost three quarters of the variation in stomatal conductance, whereas light intensity explained less than 4% of the variation in stomatal conductance. Although relative humidity had the greatest influence on stomatal conductance, air temperature was more important for photosynthesis. Xylem pressure potentials, net photosynthesis (P_n), transpiration (Tj) and water use efficiency (ratio of PyT^were poorly correlated with dry matter production.