Restoration and prescribed fire in longleaf pine ecosystems: Impacts on black carbon storage in soils

Background/Question/Methods

In the southeastern USA, vast tracts of longleaf pine ecosystems were cut and converted to agriculture after European settlement.  Of the 45 million hectares of longleaf pine originally present in the southeast, approximately 1.5 million hectares remain today.  Many of these remaining longleaf pine areas are being managed to restore fire regimes and forest composition. Prescribed fire regulates nutrient controls on productivity, forest floor and groundcover nutrient pools, as well as nutrient availability.  During burning, there is also the possibility for an input of black carbon, or charcoal remains to the soil.  Total C content beneath remnant longleaf pine-wiregrass stands can be greater than total soil C content beneath old agricultural fields and planted pine stands on old fields.  In these fire maintained ecosystems, black carbon (BC) may play a novel role in increasing soil C and potentially ecosystem C contents despite the short-term losses of aboveground biomass C during burning. This research focuses on soil carbon in the Coastal Plain landscape of the Southeast USA with a particular interest in how fire management and hardwood removal for restoration in longleaf pine ecosystems influences black carbon in soil.  

Results/Conclusions

The effects of longleaf pine management (fire) and restoration practices (hardwood removal) on total soil carbon contents were investigated at the Jones Ecological Research Center in southwestern, GA.  Managed and restored stands were compared to fire suppressed pine-hardwood stands and agricultural fields.  Surface organic material and mineral soil samples at 0-5, 5-20, and 20-50 cm were sampled based on land management regime (reference longleaf pine-wiregrass, hardwood removal for restoration, fire suppression, and agriculture) and soil type (Kandiudult, Paleudult and Quartzipsamment).  Total soil C, black C, and soot C contents were quantified.  Significant differences were found among land management and soil great group when analyzed for all categories but no significant interaction for land management by soil type was observed. Total C contents were greatest in fire suppressed areas (94 Mg/ha) while mineral soil C contents were greatest in agricultural areas (77 Mg/ha). BC (7 Mg/ha) and soot C (0.5 Mg/ha) contents were greatest in regularly burned longleaf pine-wiregrass stands.