Turkey Oak (Quercus laevis W.) Seedlings Experience Primarily Competitive Pressures, not Facilitation, from the Overstory in a Longleaf Pine (Pinus palustris M.) Ecosystem

Abstract

At a site dominated by longleaf pine (Pinus palustris Mill.) in southwestern Georgia, silvicultural plans designed to encourage ecosystem-level tolerance to climate changes - namely increased water stress - are under evaluation. One approach is to shift the hardwood component towards more xeric species, including turkey oak (Quercus laevis Walt.). This study addresses the feasibility of regenerating turkey oak seedlings in a longleaf ecosystem by investigating the relationships between overstory metrics and seedling leaf gas exchange measured over one growing season. Seedling physiological performance was negatively correlated with increased overstory levels and more stressful environmental conditions. I conclude that seedlings were negatively impacted by the overstory, with little evidence of facilitation. Efforts to transition a longleaf pine ecosystem towards greater drought tolerance may therefore be most effective when planting of turkey oak seedlings is concentrated in canopy openings. Such improvements in management techniques may aid in conserving this threatened ecosystem.