Canopy carbon and oxygen isotope composition of 9-year-old hoop pine families in relation to seedling carbon isotope composition, growth, field growth performance, and canopy nitrogen concentration

Abstract

Carbon isotope composition (δ13C), oxygen isotope composition (δ18O), and nitrogen concentration (Nmass) of branchlet tissue at two canopy positions were assessed for glasshouse seedlings and 9-year-old hoop pine (Araucaria cunninghamii Ait. ex D. Don) trees from 22 open-pollinated families grown in 5 blocks of a progeny test at a water-limited and nitrogen-deficient site in southeastern Queensland, Australia. Significant variations in canopy δ13C, δ18O, and Nmass existed among the 9-year-old hoop pine families, with a heritability estimate of 0.72 for branchlet δ13C from the upper inner canopy position. There was significant variation in canopy δ13C of glasshouse seedlings between canopy positions and among the families, with a heritability estimate of 0.66. The canopy δ13C was positively related to canopy Nmass only for the upper outer crown in the field (R = 0.62, p < 0.001). Phenotypic correlations existed between tree height and canopy δ13C (R = 0.37–0.41, p < 0.001). Strong correlations were found between family canopy δ13C at this site and those at a wetter site and between field canopy δ13C and glasshouse seedling δ13C. The mechanisms of the variation in canopy δ13C are discussed in relation to canopy photosynthetic capacity as reflected in the Nmass and stomatal conductance as indexed by canopy δ18O.