Seedling and sapling recruitment following novel silvicultural treatments in Great Lakes northern hardwoods

Abstract

Conventional forestry practices in Great Lakes northern hardwoods tend to promote the regeneration of a few economically important tree species, and may consequently contribute to a decline in mid-tolerant species abundance and tree species diversity. Using a greater variety of silvicultural systems to emulate a range of historical disturbances may help to restore historical mid-tolerant species abundance and tree diversity. To test the link between seedling recruitment and sapling recruitment and disturbance-based management systems, we implemented a novel silvicultural experiment using a variety of harvest and site preparation treatments ranging from single-tree selection to clear-cut and scarification, which emulate regionally-specific natural disturbance regimes. We predicted that mid-severity harvest treatments would promote mid-tolerant sapling recruitment, while scarification and the creation of pit-mound topography would favor recruitment of small-seeded species such as yellow birch (Betula alleghaniensis Britt.). We found that seedling and sapling composition was related to silvicultural treatment and driven by an opposing gradient of canopy openness and leaf litter depth along with temporal soil water content variation. Yellow birch seedling density, however, had little relation to silvicultural treatment but was instead predicted by positive relationships with leaf litter depth variation and residual conspecific basal area. Our findings suggest that silvicultural systems aimed at promoting species diversity in northern hardwoods should consider, along with conventional techniques, modifying litter depth and canopy openness while retaining seed trees.