Quantifying growth responses of black spruce and jack pine to thinning within the context of density management decision-support systems

Models for quantifying the growth responses of black spruce (Picea mariana (Mill) BSP.) and jack pine (Pinus banksiana Lamb.) to precommercial thinning (PCT) treatments were developed. They accounted for the increased rate of stand development arising from PCT treatments through tem-poral adjustments to the species and site specific mean dominant height-age functions. Analyti-cally, they utilized a relative height growth modifier consistent with observed density-dependent height repression effects. A phenotypic juvenile age-mature age correlation function was used to account for the intrinsic temporal decline in the magnitude of the PCT effect throughout the rota-tion. The resultant stand development patterns were in accord with theoretical and empirical ex-pectations when the response models were integrated into algorithmic variants of structural stand density management models