Early Regeneration and Structural Responses to Patch Selection and Structural Retention in Second-Growth Northern Hardwoods

Abstract

Restoration of late-successional conditions to second-growth forests has become a management objective on many ownerships. For northern hardwood forests, restoration targets include a higher abundance of large trees and coarse woody debris and greater diversity of tree species and size classes. Patch-selection harvests 0.12 ha in size were applied in conjunction with structural restoration/enhancement treatments, including within-patch legacy tree retention and downed woody debris (DWD) creation, to determine the effectiveness of these approaches at recruiting late-successional structure and intolerant and midtolerant tree species. Annual mortality rate of retained legacy trees was quite low over the 3 years postharvest (1.7%) and individual legacy tree diameter growth rate ranged from 0.2-1.0 cm yr-1. Felling and retention of culls generated within-gap DWD volumes similar to old-growth levels. Sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and striped maple (Acer pensylvanicum L.) dominated the regeneration layer 3 years postharvest in all treatments; however, abundance of intolerant (black cherry; Prunus serotina L.) and midtolerant (black and yellow birch; Betula lenta L. and Betula alleghaniensis Britton.) species was also increased in harvest gaps relative to unharvested controls. Within-gap legacy tree retention hastened sapling development, particularly of intolerant species, highlighting potential tradeoffs in achieving structural and compositional objectives with this gap-based approach.