Rare vascular flora of the longleaf pine-wiregrass ecosystem: temporal responses to fire frequency and population size.

Abstract

We examined factors likely to be important in the management of rare flora occurring in the longleaf pine-wiregrass ecosystem on Fort Bragg and Camp Mackall Military Reservations in North Carolina. Thirty-six rare plant species, comprising 1,268 records, were documented during the course of two inventories of rare flora conducted during the periods 1991-93 and 1998-99. There were 891 (70.3%) records of persistence, 258 (20.3%) records of extinction, and 119 (9.4%) records of colonization; extinctions exceeded colonizations by 139 records. We used analyses of contingency table frequencies and logistic regressions to test hypotheses about temporal responses of local populations of rare flora. We found statistically significant effects of fire frequency on the colonization and extinction of rare flora; extinctions declined and colonizations increased with increasing fire frequency. There were statistically significant effects of both area occupied and stem number on the persistence and extinction of rare flora; extinctions declined and persistences increased with increasing area occupied and stem number. Relative turnover of rare flora was correlated with mean fire frequency and mean stem number. Relative turnover increased with increasing fire frequency and declined with increasing population size. Our analyses indicate the importance of fire and population size for the conservation of rare flora in this landscape.