Diameter and death of whorl and interwhorl branches in Atlas cedar (Cedrus atlantica Manetti): a model accounting for acrotony

Branch size and branch status (dead or alive) are important characteristics closely related to tree growth and wood quality. The aim of this study was to design models for the diameter and status of branches in Atlas cedar (Cedrus atlantica Manetti). The models were developed from data collected on a set of 32 trees with a wide range of heights (from 3 to 36 m), girths (from 13 to 226 cm), and ages (from 20 to 95 years). A single general segmented model was designed for both whorl and interwhorl branch diameter, taking into account the tree and annual growth unit random effects. The model’s “potential x reducer” form describes the maximum branch diameter profile along the tree and the acrotonic gradient observed in annual shoots. The diameter and status of every branch were modeled based on the vertical position on the trunk and on the height of the base of the living crown. The tree diameter and the branch diameter were used as additional explanatory variables in the branch diameter model and the branch status model, respectively. The model structure is sufficiently general to be suited after re-parameterization for many coniferous species with interwhorl branches such as Spruces, Firs, and Larches.