Possible ecological mechanisms for loss of vernal-herb diversity in logged eastern deciduous forests

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.