Tradeoffs in forest carbon dynamics, fire management, and red-cockaded woodpecker habitat in longleaf pine ecosystems

Background/Question/Methods

Forests provide many ecosystem services, including significant carbon storage that can offset anthropogenic greenhouse gas emissions.  Balancing carbon storage and ecosystem function in forests that evolved with frequent, low intensity fire regimes may require tradeoffs. Although fire exclusion increases carbon storage in some frequent fire forests, such action may increase wildfire risk and cause biodiversity loss. Restoration and management of these forests results in carbon emissions whether in the form of prescribed fire or mechanical thinning.  We evaluated the carbon storage and emissions  of fire-excluded and fire-maintained longleaf pine (Pinus palustris) forests at Ft. Benning, GA. Longleaf forests support high levels of plant diversity and provide habitat for wildlife species of concern including the gopher tortoise (Gopherus polyphemus) and federally endangered red-cockaded woodpecker (Picoides borealis) but are restricted to approximately 3% of the original range. Older longleaf stands at Ft. Benning provide important woodpecker habitat, and younger stands are managed to provide future habitat. We compared the carbon dynamics of management in young (< 30 years at sampling), maturing (30-75 years at sampling) and older (>75 years at sampling) forests. We simulated control, prescribed burning, and red-cockaded woodpecker management (fire and density thresholds) treatments using the Forest Vegetation Simulator.

Results/Conclusions

Forest carbon storage and conservation of the longleaf pine ecosystem can be complimentary objectives, although management results in carbon losses. Over 50 years, simulated control stands of all age classes stored approximately 20 Mg C ha^-1 more aboveground live carbon than stands managed with prescribed burning every 3 years. Thinning younger stands to encourage the development of woodpecker habitat removed approximately 10.8 Mg C ha^-1 and regular prescribed fire emitted on average of 2.4 to 3.1 Mg C ha^-1 depending on forest age.  However, carbon losses from fire were usually recovered within the fire return interval. Even when burned every three years, forests of all age classes continued to sequester carbon. Over 50 years, mean aboveground live carbon stores increased by 64 Mg C ha^-1 in young stands, 24.4 Mg C ha^-1 in maturing stands, and 30.4 Mg C ha^-1 in older stands. In the absence of regular fire, ecosystem conversion results in hardwood succession.  Hardwoods exclude groundcover plants and do not support longleaf associated wildlife. Although conservation necessitates some carbon tradeoffs, longleaf forests provide a sustained carbon sink as part of a suite of ecosystem services.