Did Native American fires maintain the longleaf pine ecosystem? A paleoecological approach

Background/Question/Methods

The longleaf pine savanna of the southeastern United States has been declining in areal extent during the past 300 years. Many factors contribute to this decline, including timber harvesting, land clearance and conversion. However, frequent surface fires are recognized as a primary factor in maintaining longleaf pine dominance. Missionary accounts from 16^th century document that pre-Columbian populations in the southeast region used fire for agricultural and hunting purposes, suggesting that longleaf pine savannas were maintained by human-set fires.  Regional Native American populations declined and societies collapsed during the 16^th Century after introduction of diseases and military assaults by the deSoto Expedition and other European parties.  We hypothesize that, if Native American cultural practices were responsible for maintaining the longleaf pine ecosystem, reduction of fires in the 16^th and 17^th Centuries should have led to invasion of longleaf pine stands by oaks and slash pines and conversion from savanna to forest.  We are testing this hypothesis by examining pollen and charcoal records from lakes in the longleaf pine ecosystem.

We have obtained three lake sediment cores spanning the last 1000 years, one in north-central Florida (Sheelar Lake), one in central Florida (Leda’s Pond) and another in the Florida Peninsula (Silver Lake).

Results/Conclusions

Our preliminary data show a decrease in pine, and increasing representation of oak pollen during the last 500 years. These initial results are consistent with the hypothesis that shifts in vegetation composition and fire frequency followed disruption and decline of Native American populations in the region.  We are currently developing refined chronologies from these sites using closely spaced AMS ¹⁴C dating to identify the precise timing of changes in pollen and charcoal records.