Nonlinear Mixed-Effects Modeling of Height to Live Crown Base in Natural and Plantation Jack Pine Stands

Height to live crown base (HCB) is a key indicator of crown architecture, influencing growth allocation, timber quality, and stand dynamics in boreal forests. Accurate prediction of HCB is essential for growth and yield modeling and silvicultural planning. Using measurements from 5973 jack pine trees across 515 permanent sample plots distributed throughout Ontario, Canada, we developed and evaluated nonlinear mixed-effects models for HCB separately for natural- and plantation-origin stands. Three model families (exponential, logistic, and generalized logistic) and five predictor combinations integrating tree-level and stand-level variables were evaluated using 10-fold cross-validation.