Reconstruction of the fire history of the Florida Everglades

Vegetation dynamics in the Florida Everglades (EP) is intricately linked with its fire and climatic history.  Fire history records in EP are only available from 1948-present, which limits our ability to assess the long-term relationship to fire.  To obtain a record of fire and Cladium biomass before 1948, we measured charcoal accumulation and Cladium seed density on contiguous 1-cm sediment cores from six different sites.  Among sites, charcoal accumulation varied spatially and temporally, from nearly zero to over 80-fold.  Although we cannot yet say how much charcoal represents a fire, the variability of charcoal does indicate that an inconsistent spatial pattern of burning has occurred over the past 100 years.  Compared to the historical period (1900 AD to present), the pre-historical period (before 1900 AD) experienced far greater charcoal accumulation, indicating a 5-fold increase in burning over this period.  Specifically, charcoal accumulation rates were low from 1500 to 1900 AD.  Our findings suggest fire within the EP may have been more frequent/extensive before 1500 AD than during the past 100 years. The timing of reduced charcoal from 1500 to 1850 AD corresponds to the period of the Little Ice Age, suggesting this cold and wet climatic period perhaps may have caused reduced burning.  Based on other precipitation reconstructions, dry conditions generally correspond with increased charcoal accumulation suggesting some level of climatic control on fire.  However, increases in Cladium seed density after 1500 AD indicate a shift to Cladium dominated communities may have also contributed to the reduced fire importance.