Woody plant dynamics in a foundation conifer woodland of the Appalachian foothills, Alabama

Abstract

We documented the structure and composition of a Pinus palustris (Longleaf Pine) woodland community in the Appalachian foothills of Alabama using field measurements and investigated the drivers of forest dynamics using dendroecology paired with historical records of disturbance. Longleaf Pine dominated the canopy, exhibiting a reverse-J–shaped diameter distribution not related with age distribution. Longleaf Pines dated as far back as 1669 to as recently as the early 2000s. In contrast to many other forests, the spatial distribution of Longleaf Pine stems in our site trended toward a random distribution when trees were weighted by DBH or age. Based on ring patterns from 322 Longleaf Pine individuals, growth releases from disturbances occurred continuously from the early 1900s through the 1940s and between 1985 and 1995, with Longleaf Pine establishment peaking 3 times: in the 1880s, 1940s, and 1990s. A superposed epoch analysis revealed that release events were not related with recorded large-scale meteorological (e.g., hurricanes) or local human-induced disturbances, suggesting that other factors have influenced the dynamics of this community. This Longleaf Pine community in the Piedmont shared similarities in composition and structure to other Longleaf Pine communities of the southeastern United States. A combination of fire suppression over the last 80 years and high-intensity arson fires over the last decade has caused an increase in density of both live and dead Longleaf Pine and recruitment of fire-sensitive pines and hardwoods into the seedling/sapling classes and canopy. Restoration of the historical fire regime may be needed for Longleaf Pine to maintain its dominance in this community, as fire may have appeared to exert strong control over the dynamics of this community.