Hardwood-Cypress Swamps, Unlikely Fire Hazards

Management of border between swamps and pine flatwoods is critical

thin pine trees tower over a flat grassy area
Pine flatwood forest in Florida. This forest type typically burns every few years and is necessary to sustain the forest’s health. Photo by Scott Zona, courtesy of Wikimedia Commons.

In parts of the southeastern U.S., one unlikely forest type has great potential for extreme fire behavior: hardwood-cypress swamps. These shallow wetlands can work with their more frequently burned neighbors, pine flatwoods, to wreak havoc by easily igniting and sustaining tremendous wildfires, thus depleting carbon storage in these forests.

Hardwood-cypress swamps and pine flatwoods are the focus of a recent study by Dan Krofcheck of the University of New Mexico, Albuquerque, USDA Forest Service researcher Louise Loudermilk, and colleagues. The study was published in the journal Ecosphere.

The group examined long-term management practices during extreme fire weather across these connected ecosystems. They asked, where and to what extent could fire management be used to most effectively suppress wildfires and continue storing carbon?

At the Osceola National Forest in Florida, where this study was conducted, the flatwoods and swamps are mixed together across its vast landscape, making fire management tricky. Pine flatwoods typically contain longleaf pines (Pinus palustris) and are managed with prescribed fire, applied every few years, and timber harvesting.

These forests are economically valuable for southeastern states through timber, hunting, recreation, and other Hardwood-cypress swamps are not actively managed and are typically flooded with water, making fire unlikely to occur. But when water levels are low or nonexistent, the dry floor can easily ignite and produce very intense fires. Maintaining forest carbon can lead to environmental stability, enabling the continued use of the forest’s resources. The wildfires within these environments can be mitigated by prescribed fire and other forms of land management, leading to questions that this article attempts to answer.

“Counterintuitively, the removal of fire is really the disturbance in pine flatwoods because when fire is removed, it will quickly change the pre-existing ecosystem to another ecosystem within a couple of decades,” says Loudermilk. “If we were to cease prescribed fire on this landscape, how would that change this endangered ecosystem and long-term carbon stocks given the inevitable onset of future wildfires?”

Hardwood-cypress swamp in Florida. Although the floor of this environment is typically covered in water, climate change is leading to drier conditions leading to a greater potential for fire. Photo by National Park Service, courtesy of Wikimedia Commons.

With wildfire data from the national forest and Forest Inventory Analysis data, the researchers used the LANDIS-II model to simulate wildfires and carbon storage conditions in the national forest. In the model, the team used climate data from the U.S. Geological Survey to define extreme fire weather conditions and local management parameters, including prescribed burning and forest thinning.

Model simulations showed that actively managing pine flatwoods decreased both the extent and magnitude of wildfires under both contemporary and extreme fire weather conditions – particularly when forest management techniques were applied to the borders between the pinelands and swamplands.

Carbon sequestration levels did not change drastically under moderate fire conditions. “In extreme fire weather conditions, however, there was a significant difference,” says Loudermilk. This difference resulted in a substantial amount of carbon retained in the forests by continued active management during extreme fire weather.

These extreme fire weather conditions are representative of the future climate-fire environment. Climate change is playing a significant role in southeastern forests – more frequent and variable hot and dry periods lead to conditions that are more conducive to hazardous wildfires, especially in the swamplands.

Because these unique forest environments are integral to southeastern economies and house invaluable flora and fauna, it is crucial to ensure sustainable use and management.

By focusing on managing the borders between the two forest types, forest managers can “maintain a diverse landscape, while protecting the wetlands and nearby communities,” says Loudermilk, and ensure that future wildfires remain manageable. Without the management of these borders, climate change could have devastating consequences in the fast-approaching future.

Learn more about extreme fire scenarios in the southeastern US.

For more information, email Louise Loudermilk at eva.l.loudermilk@usda.gov.

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