Fire dependence of longleaf pine regeneration: An examination of the evidence and implication for restoration

Longleaf pine (LLP; Pinus palustris) is one of the seven Pinus species in the world that have evolved a grass stage. This unique adaptation presumably helped LLP achieve its past dominance in the frequently burned coastal plains and sandhills of the southeast United States, and contributed to the twentieth century losses of LLP subjected to a fire regime much altered from the historic regime. With increasing efforts directed toward restoring LLP ecosystems, understanding the fire dependence of LLP regeneration is essential. Although there is abundant literature describing the adaptation of juvenile LLP to fire and the role of fire in LLP regeneration, most of these reports were generated from field observations not from experimental studies. Because LLP seedling development is likely controlled by complex interactions among several factors, the lack of designed experiments precludes answering a number of important questions.  For example, what determines the duration of the grass stage of LLP seedlings? What mechanism triggers height growth? Can fire directly stimulate height growth? Is there geographical variation in the fire adaptation of LLP? How can prescribed fire be used effectively to facilitate the establishment of longleaf pines? Based on a critical examination of documented evidence, we assess and discuss future research needs regarding LLP fire adaptation and its implications for restoring the LLP ecosystem through natural and artificial regeneration.