Print PageFire is an important disturbance in a variety of ecosystems and can have multiple direct and indirect effects on the population dynamics of many plant species. In the southeastern United States, the longleaf pine ecosystem is dependent on frequent fire, and fire suppression in the last century has led to dramatic population declines of many endemic plant species. Although the reintroduction of fire has been successful at restoring or stabilizing a number of these species, there is uncertainty about the appropriateness of adopting universal fire regimes for all species. In a three-year demographic study, we collected information on the vital rates of Pyxidanthera brevifolia, a plant endemic to the Fall-line Sandhills region of North and South Carolina that is vulnerable to extinction. We used these data to model the vital rates, construct transition matrices, and project stochastic population growth.
Results/Conclusions
In contrast to findings from studies of other endemic species in the longleaf pine ecosystem, fire had a negative effect on the vital rates of P. brevifolia, causing reduced survival, flowering, and capsule production. Additionally, stochastic population projection simulations suggested that under higher fire frequencies (< 3 years), P. brevifolia would have reduced population growth. Several lines of evidence suggest that over the last 20 000 years fire has not been as frequent as the estimated fire-return interval of the past 500 years. Although the current longleaf pine ecosystem is fire dependent and has burned frequently for at least several thousand years, we propose that P. brevifolia may be a “holdover” from a past vegetation community. Despite the negative direct effects of frequent fire, however, the current fire return interval may indirectly benefit P. brevifolia by reducing woody encroachment and removing litter.
