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Carbon Consequences: Modeling Future Fire Risk in North Florida

Extreme fire weather events are the major driver of wildfire in the Southeast, and prescribed fire is our best tool for mitigating those wildfires. Some specific landscapes in the region are particularly prone to large wildfires, including the swamps and pine flatwoods connecting the Okefenokee National Wildlife Refuge to the Osceola National Forest. One of the unlikely forest types in that landscape that can contribute to extreme fire behavior are hardwood-cypress swamps. Under certain conditions, these ephemeral wetlands can work with their more frequently burned neighbors, pine flatwoods, to sustain immense wildfires, cause substantial smoke emissions, and deplete carbon stores in these forests. Pine flatwoods typically contain longleaf pines (Pinus palustris) and are managed with frequent prescribed fire and timber harvest.

Our colleagues, Dan Krofcheck and Matthew Hurteau at the University of New Mexico, and Robert Scheller at North Carolina State University worked with us on a recent study published in the journal Ecosphere and funded by the USDA Forest Service, Joint Fire Science Program to examine these complex interactions. At the Osceola National Forest in Florida, our group examined long-term management practices during extreme fire weather across these two vastly different, yet intertwined ecosystems.

Like the longleaf pine forests in most of North Florida, the removal of fire is really the disturbance in pine flatwoods because, without fire, southern pine forests can quickly accumulate fuel loads for wildfire or eventually transition to a hardwood or shrub ecosystem within a few decades. This study looked at future forest outcomes of removing prescribed fire, using prescribed fire while targeting harvests in zones adjacent to wetlands, or leaving a standard rotation of prescribed fire within the landscape. We asked, what were the changes in wildfire, ecosystem and long-term carbon stocks given the inevitable onset of future wildfires under these management scenarios and anticipated changes in extreme fire weather?

We found that targeted placement and frequent application of management can limit large wildfires and maintain ecosystem carbon stocks through time. Model results showed that targeting overstory thinning treatments to the interface of the hardwood–cypress swamps and maintaining the pine flatwoods edges with prescribed burning limited the spread of high‐severity wildfire at the landscape scale during severe droughts. This strategy also maintained more stable landscape carbon levels. This study highlights the importance of understanding how changes to fire weather severity may alter future fire regimes and consequently carbon stability of these highly interspersed yet functionally dissimilar ecosystems. Optimizing prescribed fire and timber harvest at the landscape scale is critical to managing these risks in regions where wetlands can contribute to large fire growth, particularly during drought. This strategy sustains forest carbon which also leads to environmental stability, enabling the continued use of the forest’s resources, including hunting, birdwatching, and recreation regardless of changes in future drought severity.

Read more here: https://www.srs.fs.usda.gov/compass/2020/07/07/hardwood-cypress-swamps-unlikely-fire-hazards/

Read the study in Ecosphere here: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.2631

 

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