Untangling the Mystery of the Barrens: Long-Term Fire Records from Tennessee and Missouri, U.S.A.

Unique barrens ecosystems with open canopies and diverse herbaceous plant species were once more widespread in certain areas of the eastern United States. Today these barrens require disturbances such as fire to maintain open habitat for the array of plant and animal life they support. But how long has fire played a role in shaping these systems? From study sites of Westall Swamp, in the historic Barrens area of middle Tennessee, and Cupola Pond, located near barrens in southeastern Missouri, long-term fire records were created to investigate the timescales over which fire has played a role in these landscapes. Macroscopic and microscopic charcoal records were created for Westall Swamp from a sediment core recovered in 2023, and a microscopic charcoal record was created for Cupola Pond using pollen slides originally prepared for a 1984 thesis on vegetation change by University of Tennessee student Everett Smith, Jr., based on a core recovered in 1983.

Records from both sites preserve evidence of fire in the earliest sediments analyzed, which dated to ca. 26,000 cal yr BP at Westall Swamp and 18,000 cal yr BP at Cupola Pond. Macroscopic charcoal concentrations and influx at Westall Swamp declined to very low values between ca. 20,000 cal yr BP and 8000 cal yr BP, except for a spike around 12,500 cal yr BP, before increasing dramatically after 3000 cal yr BP and again after ca. 1000 cal yr BP. Microscopic charcoal at Westall Swamp, examined at lower resolution, showed less variation, but concentration and influx values also peaked in the last ca. 1000 years. At Cupola Pond, microscopic charcoal influx and charcoal:pollen ratios both declined sharply at 15,000 cal yr BP, followed by small peaks in the record at 11,000 and ca. 7000 cal yr BP. Charcoal concentrations also peaked at ca. 7000 cal yr BP, in line with grass pollen percentages in the core as determined by Smith, suggesting that increased fire could be tied to a more open habitat with abundant grass.