Les coupes partielles : une alternative à la coupe à blanc dans les peuplements mixtes de sapin baumier et d'épinette rouge en termes de rendement

Abstract

A non-linear model is proposed to describe the growth evolution in mixedwood stands composed of balsam fir (Abies balsamea (L.) Mill.) and red spruce (Picea rubens Sarg.) following a diameter-limit cutting. All softwood stems having a stump diameter equal to or greater than 18 cm were removed during this cutting. The model approach considers the entire stand where the volumes of the two main species, balsam fir and red spruce, were individually modeled. The model was also calibrated for two forest sites identified using Heimburger (1941) forest sites plant index: Cornus and Oxalis-Cornus. On average, the rotation periods suggested by the model range from 25 to 30 years with yields of 4.0 m 3 ha –1 ear –1 of merchantable volume. In the Cornus forest site, the diameter-limit cutting enables maximization of the yield while maintaining red spruce dominance. In the Oxalis-Cornus forest site, the volume removal has been too important and residual stands were under optimal growth conditions. Furthermore, the cutting has favoured balsam fir instead of red spruce. A reduction of volume removal and an integral protection of red spruce stems having a diameter less than 35 cm at breast height would enable maximization of the yield and maintain the species proportions. Under the Quebec forest context, the selection method would constitute an adequate operation in stand management of forest sites corresponding to Oxalis-Cornus, while cutting with retention of small merchantable stems would be applicable to stands corresponding to the Cornus site. Key words: red spruce, balsam fir, mixedwood stands, productivity, modelling, partial cutting, yield, composition, silviculture