Growth and self-thinning of shortleaf pine resprouts following wildfire: Eleven-year dynamics in a mixed pine-hardwood forest

Frequent fire supports the regeneration and sustainability of shortleaf pine ( Pinus echinata Mill.)-oak ( Quercus spp.) mixedwood forests that have declined across the eastern United States. Shortleaf pine is adapted to fire through its ability to resprout following topkill, so understanding post-fire resprouting dynamics can inform successful regeneration strategies. We characterized the resprouting response of naturally regenerated shortleaf pine in a mixed pine-hardwood forest following a dormant-season wildfire in the upper Piedmont of South Carolina. Resprouting response was measured one, two, three, five, and 11 growing seasons after the fire, and we quantified self-thinning dynamics, height growth, and diameter growth through time and in relation to parent tree size and resprout quantity. All repeatedly measured resprouting pines survived through three growing seasons. Initially dense clusters of resprouts experienced rapid self-thinning, with mean live resprout quantity per tree decreasing from 29 to six between the first and third growing seasons. Most resprouting trees possessed only one live stem by the fifth growing season. Tallest resprout height growth and early resprout quantity were positively related to the initial basal diameter of the topkilled parent tree. After 11 growing seasons, shortleaf pine was dominant in the largest size classes of regeneration and comprised > 60 % of stand basal area. Associated hickory ( Carya spp.) and upland oak species were abundant in smaller size classes. These results help to clarify the role of fire in shortleaf pine regeneration and can inform the use of prescribed fire as a silvicultural tool in shortleaf pine restoration. • We measured the resprouting response of shortleaf pine after topkill by wildfire. • On average, resprouting pines self-thinned from 29 to one stem within five years. • Resprout quantity and height growth increased with pre-fire parent stem size. • Resprouting facilitated shortleaf pine regeneration and recruitment after the fire.