Factors associated with postlogging paper birch decadence in residual stands

Following harvesting operations within the Quebec mixedwood region, decaden ce symptoms are frequently observed on residual paper birch trees, compromi sing future harvests. Simultaneously, these residual stands are often a con straint to the establishment and growth of valuable regeneration. In the co ntext of intensive forest management and preservation of the conifer compon ent in mixedwood stands, it is important to identify factors associated wit h paper birch post-logging decadence. Ninety-eight (98) stands were sampled along a partial cutting chronosequence of I to I I years old in order to e xamine five site variables and six stand variables susceptible of explainin g post-logging decadence. Classification and regression tree (CART) models indicated that stand variables, mainly residual basal area and time since h arvest, were the best predictor variables of decadence. This study suggests maintaining a basal area of at least 16 m(2)/ha and preserving larger diam eter stems when the objective is to maintain healthy paper birch for furthe r harvesting. When the silvicultural objective is to regenerate softwoods, this study recommends keeping a residual basal area after partial cutting o f no more than 4 m(2)/ha.