EsPaCe: A growth model for balsam fir stands following precommercial thinning in Québec, Canada

Precommercial thinning reduces the density of young, high-density stands, promoting the growth of selected trees. However, existing growth models are calibrated for merchantable-sized trees and do not account for saplings, which limits their ability to simulate the changes induced by precommercial thinning. To address this gap, we developed EsPaCe, a growth simulator tailored to balsam fir stands treated with precommercial thinning. Using data from 329 plots monitored over 20 years post-treatment, we calibrated six interconnected models to predict stem density, species composition, and diameter distribution at 5-year intervals. Simulation results in the balsam fir–paper birch domain show that balsam fir (Abies balsamea (L.) Mill.) remains largely dominant after treatment. Initial stand conditions (density, composition, and quadratic mean diameter) had little effect on the final stand composition. However, later interventions in stands with higher initial quadratic mean diameters appeared to promote tree diameter growth and provide slight control over species composition. Model predictions remained unbiased over 20 years, and simulations extended to 35 years produced plausible outcomes. EsPaCe provides forest managers with a valuable tool for planning silvicultural treatments and integrates seamlessly with long-term growth models for merchantable stands.