The maintenance of understory residual flora with even-aged forest management: A review of temperate forests in northeastern North America

This study reviews the effects of even-aged forest management (primarily clearcut logging) on the dynamics, structure, and composition of understory vascular plant communities in remnant late-successional (old-growth and old re-growth) forests of northeastern North America. Less than 1% of forested land in the region has never been cleared and remnant patches of primary woodland (i.e., continuously forested since European colonization; ~350 BP) are few, small and isolated within a second-growth landscape that is increasingly managed in open and immature forest age-classes. The historical loss and fragmentation of pre-settlement forested habitat has generated considerable scientific and public debate about whether additional declines in late-successional woodland, as a result of contemporary land uses (e.g., clearcut logging), threaten species that are associated with old forest conditions. We focused particular attention on residual plants (i.e., flora associated with late-successional forests) that may be dependent upon older stand conditions for maximal growth or that are less common within intensively managed landscapes. Despite a general community-wide resiliency to clearcutting, we found that a number of residual plants in northeastern forests are typically eliminated or have a reduced presence in recovering stands after logging (e.g., Oxalis montana (L.), Aralia nudicaulis (L.), Taxus candensis (Marsh.)). The most sensitive species to clearcutting include mycotrophs, taxa with limited seed dispersal and (or) low rates of clonal expansion (<10 cm/year), and species reliant on specific seedbed conditions associated with older forests (e.g., decayed logs). These results suggest that the preservation of remnant late-successional forests (both old-growth and old re-growth) may be necessary for the maintenance of some residual plant populations in highly disturbed and fragmented forest landscapes in the northeastern North America.