Polymorphic site index equations for four New Brunswick softwood species

As part of a provincial forest site classification program, polymorphic site index equations were developed for Pinusbanksiana Lamb., Piceaglauca (Moench) Voss, Piceamariana (Mill.) B.S.P., and Abiesbalsamea (L.) Mill. in New Brunswick using a generalized version of the Chapman–Richards' height-growth model and data from stem analysis of dominant and codominant trees growing on a wide range of sites. Two generalized five-parameter versions of the Chapman–Richards' model were tested. The resulting equations explain from 96 to 98% of the variation in dominant tree height using breast-height age and site index as independent variables.