Life Stage and Neighborhood-Dependent Survival of Longleaf Pine after Prescribed Fire

Abstract

Determining mechanisms of plant establishment in ecological communities can be particularly difficult in disturbance-dominated ecosystems. Longleaf pine (Pinus palustris Mill.) and its associated plant community exemplify systems that evolved with disturbances, where frequent, widespread fires alter the population dynamics of longleaf pine within distinct life stages. We identified the primary biotic and environmental conditions that influence the survival of longleaf pine in this disturbance-dominated ecosystem. We combined data from recruitment surveys, tree censuses, dense lidar point clouds, and a forest-wide prescribed fire to examine the response of longleaf pine individuals to fire and biotic neighborhoods. We found that fire temperatures increased with increasing longleaf pine neighborhood basal area and decreased with higher oak densities. There was considerable variation in longleaf pine survival across life stages, with lowest survival probabilities occurring during the bolt stage and not in the earlier, more fire-resistant grass stage. Survival of grass-stage, bolt-stage, and sapling longleaf pines was negatively associated with basal area of neighboring longleaf pine and positively related to neighboring heterospecific tree density, primarily oaks (Quercus spp.). Our findings highlight the vulnerability of longleaf pine across life stages, which suggests optimal fire management strategies for controlling longleaf pine density, and—more broadly—emphasize the importance of fire in mediating species interactions.

The unexpected influence of legacy conspecific density dependence

“…Negative conspecific density dependence (CDD) can be a stabilizing mechanism for species coexistence when it is more negative than heterospecific density dependence (Adler et al, 2007;HilleRisLambers et al, 2012;Hülsmann et al, 2021Hülsmann et al, , 2024. Many studies have quantified the density-and distance-dependence effects of living conspecific trees on neighbouring seedlings and tree vital rates, yielding valuable insights into patterns of recruitment, growth and survival (e.g., Comita et al, 2010;Jevon et al, 2022;Magee et al, 2022). These analyses often evaluate survival as a function of distance-and size-weighted neighbourhood crowding indices (Comita & Hubbell, 2009;Jevon et al, 2020;Johnson et al, 2017;Smith, 2022), finding that the presence of large neighbouring trees decreases seedling, sapling and tree survival (Piao et al, 2013;Pu & Jin, 2018;Yao et al, 2020;Zhu et al, 2015).…”

Hardwoods influence effect of climate and intraspecific competition on growth of woodland longleaf pine trees

“…Competition has been less studied in open‐canopy forests such as longleaf woodlands. There are indications that mature hardwoods may facilitate longleaf pine establishment in drought‐prone sandhills (Johnson et al, 2021; Loudermilk et al, 2016; Magee et al, 2022), but whether this phenomenon may extend to interactions among mature trees, and on more productive sites, is not known.…”

Spatial Multi-Criteria Decision Modeling for Pinus palustris Mill. (Longleaf Pine) Restoration in the South Carolina Sandhills Wiregrass Gap

“…Generally, when the root collar diameter of a grass-stage Longleaf Pine reaches ≥2.56 cm, it will initiate rapid height growth (i.e., bottlebrush or bolt stage), which removes the terminal bud from within the flame length of most low-intensity surface fires (Brethauer et al 2021, Hatchell and Marx 1987). As the tree enters the sapling stage, bark thickness increases to prevent girdling (Eberhardt 2013, Magee et al 2022), and sexually mature individuals, ∼30 years old, start to naturally prune lower branches, and form tall (18–34 m), straight boles (Boyer and Peterson 1990).…”