Pine flatwoods of the Southeastern Coastal Plain are primarily composed of an overstory of longleaf pine (Pinus palustris) and slash pine (P. elliottii), with the latter being the primary component in hydric communities. A frequent fire regime of 3-5 years maintains the structure of these communities. While much is known about the tolerance of longleaf pine to fire, little is known about slash pine tolerances. We conducted this study to determine the fire tolerance factors of slash pine regeneration so as to restore and maintain the natural historic structure of these communities. Within four 5x5m plots of a slash pine dominated wet flatwood site in north-west Florida, we counted and measured all slash pine seedlings and saplings and classified them into height classes ranging between 0 to 8m. To determine prescribed fire temperature and duration, we systematically placed five sets of thermocouples within each plot at four heights (0, 66, 132, 200 cm) above the ground. The thermocouples were programmed to record temperature once every 10 seconds. Prescribed fire was then implemented as a treatment via aerial and ground ignition in March 2018.
Results/Conclusions
Temperature exposure above 60°C, the lethal temperature for most plant tissue, ranged from 70-220 seconds in different plots, with an average temperature of 122°C. At one month after treatment, percent crown scorch, stem scorch, and foliar consumption of the seedlings and saplings were recorded. All tree regeneration under 1m tall in all plots displayed 100 percent crown scorch, 80-100 percent stem scorch, and 60-100 percent foliar consumption. These trees were considered dead. Initial observations suggest that slash pine seedlings shorter than 1 m tall are unlikely to survive fire regardless of intensity, and, therefore, if natural regeneration is desired, fire should be avoided during this stage. All tree regeneration above 1m tall in all plots displayed 40-100 percent crown scorch, 10-100 percent stem scorch, and 0-100 percent foliar consumption. Future assessment of plots at both six months and one year post treatment will be done to indicate mortality of the taller than 1m height classes.