Background/Question/Methods Longleaf pine (Pinus palustris Mill.) forests only occupy a small fraction of the Southern United States landscape they once dominated prior to European settlement, with natural stands being an even smaller fraction. Longleaf pine is the keystone species in several threatened and endangered species habitats as well as a very valuable crop tree.  Efforts are already underway to restore these forests and habitats to the landscape. Sustaining natural stands is often overlooked in the restoration effort, but it is vital to maintaining sustainable structure for habitats and regular income without the need for or cost of intensive site preparation and planting. Mortality associated with longleaf pine is an important and very dynamic question when looking at managing longleaf pine for a variety of objectives. A better understanding of mortality can affect management practices like using prescribed fire, thinning regimes, and regeneration methods for the forests of today and the forests of the future. To assess and evaluate mortality in natural even-aged stands of longleaf pine, permanent plot data from the U.S. Forest Service Regional Longleaf Pine Growth Study (RLGS) have been analyzed.
Results/Conclusions In 1964, the U.S. Forest Service established the RLGS to study longleaf pine stand dynamics.  Data from the RLGS cover a range of age classes, basal area classes, site indices, and ecoregions across the southern United States. Plots have been measured every five years since the establishment of the study, and the database contains a history of burn frequency, plot density, and the location of each tree on a plot.  Mortality is also assessed every five years to determine if trees died due to lightning, insects, disease, windthrow, mechanical damage, fire, trespass cutting, suppression, or unknown causes. The plots are thinned as needed to maintain the assigned basal area classes. The dataset provides over 40 years of measurements with the 45^th measurement already underway.  The maintained basal area classes mimic stand densities from stand replacement regeneration cuts to single tree selections and high density stands left to grow.  Results from these densities across a range of sites show trends in mortality over four decades and provide insights about the effects of management options for natural stands with implications for the future management of longleaf pine.