© 2003 Heron Publishing—Victoria, Canada
Branchlet nutrient concentration in hoop pine (Araucaria cunninghamii) relative to family, stable carbon and oxygen isotope ratios and growth rate in contrasting environments
N. V. Prasolova (1) and Z. H. Xu (2, 3, 4)
1. Faculty of Environmental Sciences, Griffith University, Nathan, Queensland 4111, Australia / 2. Queensland Forestry Research Institute, P.O. Box 631, Indooroopilly, Queensland 4068, Australia / 3. Cooperative Research Centre for Sustainable Production Forestry, Griffith University, Nathan, Queensland 4111, Australia / 4. Author to whom correspondence should be addressed (zhihong.xu@dpi.qld.gov.au) / Received August 9, 2001; accepted October 26, 2002; published online June 2, 2003
Summary
Genetic variation in branchlet nutrient (N, P, K, Na, Ca, Mg, Mn and Fe) concentrations and mineral concentration (sum of
branchlet P, K, Na, Ca, Mg, Mn and Fe concentrations) of 8–9-year-old hoop pine (Araucaria cunninghamii Ait. ex D. Don) half-sib families was assessed for four canopy positions at a wet site (23 families) and two canopy positions
at an N- and water-limiting dry site (22 families) in relation to tree growth and associated branchlet carbon (δ13C) and oxygen (δ18O) isotope composition in southeast Queensland, Australia. Branchlet nutrient and mineral concentrations varied significantly
among families and with canopy position and site. Depending on the canopy position sampled, the hoop pine family effect accounted
for 0 to 13.8% of the total variation in branchlet N concentration, and for 0 to 30.3% of the total variation in branchlet
mineral concentration at the wet site. The corresponding values for the family effect at the dry site were 0–13.3% for branchlet
N concentration and 0–25.7% for branchlet mineral concentration. There were significant variations in branchlet P, K, Ca and
Mg concentrations at both sites, and these variations differed with canopy position. Relationships between family means of
branchlet N concentration and tree growth or δ13C or δ18O varied with canopy position at both sites. At the wet site, there were significant positive correlations between branchlet
mineral concentration in the upper-outer or upper-inner canopy and tree height (r = 0.26 and 0.37, P < 0.01) and between branchlet mineral concentration and δ13C (r = 0.24, P < 0.01) in the upper-inner canopy, and a significant negative correlation between branchlet mineral concentration and δ13C (r = –0.21, P < 0.05) in the upper-outer canopy. At the dry site, branchlet mineral concentrations in the upper-inner and upper-outer canopy
were significantly correlated with branchlet δ13C (r = –0.28 and –0.51, P < 0.01), and branchlet N concentration in the upper-inner canopy was significantly correlated with tree growth (r = 0.29, P < 0.01). A significant correlation between branchlet δ18O (an index of stomatal conductance) and branchlet mineral concentration at the dry site (r = 0.39, P = 0.020) indicated that stomatal conductance might be a factor regulating the variation in branchlet mineral concentration
of the hoop pine families. Both branchlet N concentration and mineral concentration at particular canopy positions assist
in selecting hoop pine families with improved tree growth and N- and water-use efficiency in environments where both N deficiency
and a limited water supply are major factors affecting plantation productivity.
Keywords:
carbon isotope composition, oxygen isotope composition, stomatal conductance, water-use efficiency.
