Short-term vegetation responses to the first prescribed burn in an urban pine rockland preserve

Abstract

BackgroundPreserving fire-dependent ecosystems can mitigate biodiversity loss from urbanization, but prescribing fire is challenging near human habitation. Consequently, dereliction of fire-dependent forests is widespread in urban fragments. Natural disturbance-based management, like prescribing fire, is gaining global acceptance, yet it is unclear what affects prolonged exclusion have on the initial regeneration of isolated plant communities immediately after fire is reintroduced. We took advantage of the first prescribed low-intensity burn on a university pine rockland nature preserve in South Florida, USA, to gain insight. We measured the changes in plant community composition and vegetation cover 1 week before the prescribed burn, and again 1, 2, and 14 weeks after to assess the early and short-term stages of recovery.ResultsThe fire consumed substantial leaf litter, surface fuels, and canopy leaves, increasing sunlight availability to the understory and exposing bare ground. Many woody plants perished within a week post-burn, particularly invasive shrubs; however, germinating and resprouting plant growth were rapid. By 14 weeks, vegetation covered more of the ground than before the burn, although the upper canopy remained relatively open. Rarefied species richness was recovered by 14 weeks but did not exceed pre-burn levels. Invasive species richness was also maintained post-burn. Despite no overall changes in the community structure, our correspondence analysis and analysis of similarity of the plant community suggest high species turnover from the pre-burn to the final community surveyed, with an intermediate turnover in between.ConclusionThe endangered pine rockland ecosystem, like many fire-dependent ecosystems, is threatened by habitat loss and fire suppression. Managing urban preserves with periodic burns is essential for supporting habitat for endemic species while decreasing demands for manual and time-intensive maintenance. Our study demonstrates that seedling recruitment from early plantings of native species can contribute significantly and immediately to restoration efforts in a fire-excluded urban preserve; however, many changes were ephemeral. Supplemental burns are likely necessary to further reduce vegetation density and sustain changes to the community composition.