Reconstruction of Fire History in the National Key Deer Refuge, Monroe County, Florida, U.S.A.: The Palmetto Pond Macroscopic Charcoal Record

The pine rocklands in the Lower Florida Keys are considered endangered because of rises in sea level, urbanization, and human impacts on the natural fire regime. Macroscopic charcoal in a sediment core recovered from Palmetto Pond (24°41’45.15”N, 81°19’43.84”W) in 2010 was examined in contiguous 1-cm intervals to reconstruct Late Holocene fire history. Palmetto Pond is a shallow freshwater solution hole located within the pine rocklands of No Name Key in Monroe County, Florida. Radiocarbon dating of plant material at 247 cm depth in the Palmetto Pond profile indicates the sediment record extends back to ca. 4500 cal yr BP. Charcoal was present in every sample, a finding consistent with results from two similar pine rockland sites on nearby Big Pine Key. The Palmetto Pond charcoal record confirms that the pine rocklands of the Lower Florida Keys are a fire-dependent ecosystem characterized by frequent lightning-induced surface fires. The Palmetto Pond record contains possible evidence of climate- and anthropogenic-related influences on fire history. A large rise in fire activity from 631–329 cal yr BP may be attributed to Native American arrival and activity, drying conditions that began around the onset of the Little Ice Age, or a combination of both. An early 20th century peak in the Palmetto Pond charcoal record may record a major AD 1935 hurricane event. A companion study of tree-ring evidence of fire history on No Name Key confirms this finding and helps document a decline in fire activity coinciding with recent human settlement since the AD 1950s. An increase in the proportion of charcoal from leaf litter between 1661 and 1434 cal yr BP may indicate an interval of heightened hurricane activity