A macroscopic charcoal and multiproxy record from peat recovered from depression marshes in longleaf pine sandhills, Florida, USA

Abstract

Science-based information on historical fire frequency is lacking for longleaf pine sandhills. We undertook a high-resolution macroscopic charcoal and geochemical analysis of sediment cores recovered from three depression marshes located within a longleaf pine sandhill ecosystem in Florida, USA. A ~1500-year fire history reconstructed from >1.5 m length peat cores analyzed at decadal to multi-decadal resolution revealed abundant macroscopic charcoal particles at nearly all sampling intervals, suggesting that fire occurred near the sites for almost all decades represented in the deposit. This result supported previous hypotheses of a frequent natural fire return interval for Florida’s longleaf pine sandhills and suggested that management decisions for this ecosystem should continue to focus on the frequent prescription of controlled burns. Our research also demonstrated that some of Florida’s depression marshes contain a >3000-year archive of organic-rich peat. Bulk elemental carbon and nitrogen data and stable carbon isotope analysis of the deposits at two of the three study sites suggested persistently wet soils. Soil data from the third site suggested that drying and peat oxidation occurred periodically. These depression marshes rapidly sink carbon, with measured sequestration rates on the order of 16 to 56 g m−2 yr−1 . Our research demonstrated that Florida’s depression marshes provide an untapped record of paleoenvironmental information.