Recovery patterns of understory herbs and their use as indicators of deciduous forest regeneration

Habitat fragmentation has reduced the richness of native species of forests in northeastern North America. Despite recent large-scale increases in for est cover, studies indicate that understory herbaceous plant communities ma y take many decades to recover. We studied recovery patterns of vegetation following up to 35 years of forest regeneration in restored former cottage and road sites at Point Pelee National Park, Ontario, Canada, to assess the vulnerability of the understory herbaceous species. Overall, there were no significant differences in the diversity of native species between restore d and relatively undisturbed reference sites. There was, however, significa nt among-stite variation in the composition of the native species component of these plant communities. When only restored sites were examined, variat ion in native species composition was associated with time since site resto ration, soil moisture, canopy cover, and distance to continuous forest. Nat ive species were assigned vulnerability rankings according to their relativ e occurrence in reference and restored sites. Spring-flowering herbs, with ant- or gravity-dispersed seeds, were absent from restored sites and were d efined as highly vulnerable. In contrast, summer and fall-flowering herbs, with vertebrate- and wind-dispersed seeds, dominated restored sites and wer e less vulnerable. Species of low and intermediate vulnerability had coloni zed restored sites successfully, and the latter should function as indicato rs of recovery. In contrast, species with high vulnerability rankings had n ot recovered at all and, because of their limited dispersal ranges, may rec olonize restored sites only if they are actively reintroduced.