Fire effects on the vital rates and stochastic population growth rate of the rare shrub Lindera subcoriacea Wofford

Abstract

Understanding demographic vital rates and the factors that affect those rates are key components of successful conservation strategies for many threatened and endangered rare plant species. Lindera subcoriacea is a rare dioecious shrub that occupies isolated wetland habitats in a small number of locations in the southeastern United States. The species faces a number of threats to its continued persistence, including habitat destruction, invasive species, and population isolation. From 2011 to 2019, we collected demographic information from 290 L. subcoriacea individuals within 28 populations on Fort Bragg, North Carolina and used the data to estimate demographic vital rates in unburned populations and after being exposed to prescribed fire. We then constructed population matrices and estimated population growth rates under a 3-, 5-, and 10-year return interval. Results indicated that L. subcoriacea individuals have high survivorship in both burned and unburned populations, seed production was reduced 1- and 2-year post-fire, seed production was highly uneven across individuals, seedling recruitment was extremely low, and simulated population growth rates were only above 1.0 under the 10-year fire return interval. Taken together, these results indicate that (1) L. subcoriacea populations are persisting with population growth rates close to one, (2) the short-term impacts of fire on the overall population growth rate of L. subcoriacea, while only 2–3% may determine long-term population viability, and (3) extremely uneven seed production and limited recruitment of seedlings into larger size classes make L. subcoriacea populations vulnerable to stochastic demographic processes.