The ecological literature on eastern forest‐floor herbs and data collected in the southern Appalachians in Tennessee and North Carolina suggest five possible ecological mechanisms for reducing or limiting alpha diversity of vernal herbs in logged stands, three of which may also account for the slow recovery of some herbaceous species: (1) logging reduces populations of rarer herbs; (2) populations of forest‐floor species are further reduced during the successional stages following logging, either by inability to adapt to changed microclimate or by competition with r‐selected species that are better dispersers and better able to tolerate desiccation and increased radiation; (3) forest‐floor herbs have slow growth and reproduction rates, thus population densities increase slowly; (4) many forest‐floor herbs are clonal, ant‐dispersed, or gravity‐dispersed, thus they are slow to reoccupy suitable habitat once extirpated or greatly reduced in population numbers; and (5) logging results in less‐than‐optimal conditions for forest‐floor herb reproduction by modifying microhabitats on the forest floor and by temporarily eliminating gap‐phase succession. The data indicate some species of vernal herbs are far more tolerant of disturbance than others, and that sensitive species can be identified and utilized as indicators of community integrity and diversity.
Life history characteristics of many herbaceous understory plants suggest that such species recover slowly from major perturbations such as clear cutting. We examined herbaceous cover and richness in the understories of nine primary (“old‐growth”) forests in the southern Appalachian Mountains and of nine comparable secondary forests, ranging in age from 45 to 87 years since clear cutting. Neither cover nor richness increased with age in the secondary forests. This suggests three possibilities: (1) that recovery is so slow or variable among sites that 87 years is insufficient time to detect it; (2) that such forests will never recover to match remnant primary forests because climatic conditions are different today than when the forests became established; or (3) that herbaceous plants colonize pit and mound microtopography caused by the death of trees, so that recovery must await the growth, death, and decomposition of the trees of the secondary forest. Whatever the mechanism, herbaceous understory communities in the mixed‐mesophytic forests of the Appalachians appear unlikely to recover within the present planned logging cycles of 40–150 years, suggesting a future loss of diversity of understory herbaceous plants.
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