COMPARISONS OF PRE-FIRE AND POST-FIRE PEAT THICKNESSES, PETROGRAPHY, AND CHEMISTRY IN THE OKEFENOKEE SWAMP OF GEORGIA FOLLOWING THE FIRES OF 2007

From the 1970's through the late 80's, the senior author and his students analyzed hundreds of probe sites and cores from the peat-containing portions of the Okefenokee Swamp for their physical, chemical, botanical, and petrographic properties. This information was used to determine vertical and lateral compositions of these deposits and to reconstruct their paleoecological history. Recent prolonged droughts in the Southeast and subsequent catastrophic fires in 2007 caused deforestation of some of this swamp and loss of some unknown portions of its underlying peat deposit. Re-sampling at selected sites representing intensively burned to unburned conditions is being used to estimate the total amounts of carbon lost from this deposit to the atmosphere and other changes in peat composition. Analyses include changes in surface vegetation, elevation, and pH, and in types of plant tissues, charcoal, fungi, fecal pellets, and decomposition products in the peat. Ash, moisture, fixed C, volatile matter, and major and trace elements have also been obtained. Preliminary results show reductions in peat thickness of as much as two feet in some intensely burned areas. Evidence is also provided for severe “deflation” of domed peat surfaces during the droughts prior to burning, potentially causing errors in calculations of total carbon loss. At intensely burned sites, but before reflooding, most trace elements tended to increase significantly after burning; however, after reflooding most surficial trace elements tended to decrease. As expected, in-situ charcoal tended to differ greatly from transported charcoal. Intense burns of certain peats at near-stream sites yielded spicule-rich siliceous ash layers containing lenses of fine-grained amorphous charcoal. During some peat-burns, a narrow zone just below charring appeared petrographically to be chemically altered by heat causing resins and flavonoids to migrate, reprecipitate, and/or impregnate other tissues.