Increased levels of harvest may favour sugar maple regeneration over American beech in northern hardwoods

The increasing dominance of American beech regeneration (Fagus grandifolia Ehrh.) to the expense of sugar maple (Acer saccharum Marsh.) challenges the long-term economic viability of forest management in northern hardwoods. Based on earlier studies showing that more light in the understory favours sugar maple over beech, the irregular shelterwood system has shifted from experimental to operational over the last decade. In this paper, we evaluate the success of this shift toward irregular shelterwood for promoting sugar maple over beech by measuring the frequency, abundance of sugar maple and beech seedlings and saplings, and growth of seedlings three to six years after logging in northern hardwood forests of western Quebec, Canada. Results showed a dominance of beech regeneration regardless of the harvest intensity, particularly among tall seedlings and saplings. However, we found that the transition probability indices (projected relative combined abundance and growth) of sugar maple could be favoured, albeit to a limited extent, by an increased basal area removal, particularly where the initial occurrence of sugar maple in the advance seedling regeneration is lower than 60% and the initial beech basal area is low in the overstory (i.e. < 6 m2 ha−1). Our results highlight the importance of refining our operational management strategy to effectively limit the increasing abundance of regeneration of American beech over sugar maple in northern hardwood forests