Fire-Vegetation-Climate Interactions Across the Holocene on the U.S. Southeastern Coastal Plain

This dissertation research examined multiple proxy indicators in sediment cores from one lake and one wetland to reconstruct long-term relationships between fire, vegetation, and climate in the southeastern U.S.

At Lake Balboa (30.6992 N, 83.2031 W; 48 m elevation), a sinkhole pond located in southern Georgia, Bølling-Allerød conditions were sufficiently wet to maintain a shallow wetland at the site. Evidence for fire was minimal. Between 12,600 and 9200 cal yr BP, water availability declined, leading to a potential hiatus in sedimentation. During the early Holocene moisture availability increased, leading to greater primary productivity within and outside the lake, triggering an order of magnitude increase in fire activity. After ca. 8000 cal yr BP, deposition of terrigenous sediments increased, aquatic productivity decreased, and evidence of fire activity declined.

At Henson Branch (36.3433 E, 88.2389 W; 120 m elevation), a small spring-fed histosol on the Coastal Plain of western Tennessee, analyses of sediment cores documented the transition from a well-drained soil to a peat-forming histosol between ca. 7650–6300 cal yr BP. Oak and hickory were the dominant arboreal taxa throughout the record. Highest charcoal values occurred 7550–4650 cal yr BP, indicating more frequent or more intense fires at this time, likely linked to greater variability in precipitation. Geochemical proxies signaled a decline in primary productivity after ca. 3000 cal yr BP that led to a reduction in fire activity and cessation of peat formation ca. 800 cal yr BP.

At Henson Branch, Tennessee, peat humification and X-ray Fluorescence proxies performed on a sediment monolith tracked the development of the site from a mineral soil to a peat-forming wetland by 6560 cal yr BP, in close accord with previous studies at the site. Intervals of higher organic matter accumulation at ca. 7520–7200, 6660–6360, and 5730–5480 cal yr BP fell within a period of greater moisture variability identified in a speleothem record from Chattanooga, Tennessee. Low % transmission values throughout the record indicated enhanced decomposition of organic matter at the site through time, likely due to the slow rate of sediment accumulation at the site.