POSSIBLE ECOLOGICAL MECHANISMS FOR LOSS OF VERNAL-HERB DIVERSITY IN LOGGED EASTERN DECIDUOUS FORESTS

The ecological literature on eastern forest-floor herbs and data colle cted in the southern Appalachians in Tennessee and North Carolina sugg est five possible ecological mechanisms for reducing or limiting alpha diversity of vernal herbs in logged stands, three of which may also a ccount for the slow recovery of some herbaceous species: (1) logging r educes populations of rarer herbs; (2) populations of forest-floor spe cies are further reduced during the successional stages following logg ing, either by inability to adapt to changed microclimate or by compet ition with r-selected species that are better dispersers and better ab le to tolerate desiccation and increased radiation; (3) forest-floor h erbs have slow growth and reproduction rates, thus population densitie s increase slowly; (4) many forest-floor herbs are clonal, ant-dispers ed, or gravity-dispersed, thus they are slow to reoccupy suitable habi tat 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 tem porarily eliminating gap-phase succession. The data indicate some spec ies of vernal herbs are far more tolerant of disturbance than others, and that sensitive species can be identified and utilized as indicator s of community integrity and diversity.