Fire Ecology and Management of Loblolly Pine Forests

Forests dominated by loblolly pine (Pinus taeda) are presently the most extensive vegetation type in the Southeastern United States, encompassing a wide range of climate, soils, and topography. Loblolly pine was also widespread prior to the arrival of Europeans, but was probably limited to a much narrow range of habitats. A history of intensive agricultural land use and land abandonment, combined with intensifying forest management and changes in the historical fire regime, led to the rapid expansion of loblolly pine forests throughout the 20^th century.

Loblolly pine colonizes former agricultural fields within a decade of their abandonment if a sufficient seed source is available. These old-field stands are dominated by loblolly pine for the first several decades of forest succession. Eventually, a cohort of hardwoods establishes in the forest understory and gradually increases in dominance as the overstory pines die. Successional pathways following timber harvesting or natural disturbance often are more complex, because hardwoods establish as seedlings or sprouts along with the initial pine cohort.

Fire alters pathways of forest succession by causing mortality of existing trees, and by facilitating the establishment of new trees. Although loblolly pine seedlings and saplings are vulnerable to girdling and crown scorch, larger trees can survive most low-intensity surface fires. The establishment of loblolly pine seedlings is facilitated by high-intensity fires that kill overstory trees, expose mineral soil, and allow light to reach the forest floor. Hardwood seedlings and saplings are also susceptible to fire mortality, but can resprout vigorously from stumps and buried rootstocks. Depending on the season and frequency of burning, fires can either increase or decrease hardwood density in the forest understory. Fire can also affect forest health by influencing the susceptibility of loblolly pine to insects and disease.

Fire influences soils as well as aboveground components of the forest ecosystem. Although nitrogen and other nutrients are released to the atmosphere as gasses and particulates, the losses resulting from low-intensity surface fires typically do not lead to reductions in site productivity. Similarly low-intensity fires typically leave a layer of unburned organic matter that protects the mineral soil from post-fire erosion.

In the modern landscape, prescribed fire is commonly used as a management tool in loblolly pine forests, whereas large wildfires are comparatively rare. Prescribed burning is frequently applied as a fuel-reduction treatment to reduce the risk of catastrophic wildfire, and is particularly effective at reducing fine fuel loads. Fire can also be used in timber management for site preparation, to reduce hardwood competition, and to thin dense stands of young pine.

Because fire affects the structure and species composition of understory vegetation in loblolly pine forests, it also has a strong influence on the wildlife species that utilize these forests as habitat. Annual burning produces abundant herbs and grasses, providing food for a variety of birds and mammals. Burning at longer intervals can be effective for maintaining mast-producing trees and shrubs in the understory. The open, savannah-like forest structure produced by frequent fires is critical habitat for several threatened and endangered species such as the red-cockaded woodpecker (Picoides borealis), gopher tortoise (Gopherus polyphemus), and indigo snake (Drymarchon corais).