Radial growth of Cinnamomum kanehirae Hayata displays a larger temperature sensitivity in dominant than codominant trees

Abstract

The radial wood growth curves of Cinnamomum kanehirae Hayata (an endangered species of subtropical Taiwan) exhibit an S shape. The dominant trees displayed a larger radial growth than the codominant trees, and their growth was more sensitive to air temperature. Knowledge of wood radial growth is important for evaluating the factors that limit tree growth performance. The relevant experiments have mostly been conducted in cold and temperate ecosystems, but rarely in subtropical ecosystems. In this study, we aimed to construct a unified radial growth model for Cinnamomum kanehirae Hayata and to identify its sensitivity to temperature. The wood radial increments were quantified for 3 years by either pinning or microcoring. The radial wood growth curves were modelled integratively by semiparametric regression and individually by curve fitting. The effects of tree social class, interannual and environmental factors on radial growth were analysed quantitatively. A unified S-shaped growth model for C. kanehirae was successfully constructed. By including the social class effect, the model was significantly improved. The maximum radial increment (A) was significantly correlated with the maximum growth rate (μ); both A and μ were significantly higher in dominant than in codominant trees. The time-varying radial growth rate was more sensitive to air temperature in dominant than in codominant trees. Semiparametric models revealed an S-shaped growth curve of C. kanehirae and confirmed the higher temperature sensitivity of dominant trees compared to codominant trees in humid subtropical areas.