THE ROLE OF VEGETATION DYNAMICS IN CHOCTAWHATCHEE SAND PINE INVASION OF LONGLEAF PINE FORESTS

The expansion of Choctawhatchee sand pine (Pinus clausa) into longleaf pine forests (Pinus palustris) has been widespread on the Florida Panhandle since the early 1900s. This study examines the population-level processes of this sand pine invasion. Expansion of sand pine started by 1920, but rapidly increased in the 1940s. Population establishment and growth in invasive stands has been rapid, with establishment of many sand pine pioneer individuals followed by rapid infilling as these individuals reached reproductive maturity. Both noninvasive and invasive stands had numerous sand pine seedlings and saplings. Sand pine will likely persist in these communities in the near future. Analyses of hemispherical canopy photographs and regeneration patterns illustrate the ability of sand pine to establish under a variety of light conditions. Radial growth analysis of incremental tree cores highlights the importance of episodic wind disturbances in maintaining these sand pine populations. [Key words: sand pine, longleaf pine, Pinus clausa, Florida, pine invasion, Pinus palustris.]