Holocene Vegetational Changes in the Tombigbee River Valley, Eastern Mississippi

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Abstract
Stratigraphic studies of pollen from an oxbow on a Holocene terrace and from an upland swale near the Tombigbee River in eastern Mississippi provide a record of Holocene vegetational changes. From .apprx. 11,000 to .apprx. 7300 yr B.P. the forests were dominated by oaks and hickories. Mesic forest species were common at least locally. This suggests the existence of a significant moisture gradient between central Mississippi-Alabama and the vicinity of Goshen Springs (Delcourt, 1980) in southern Alabama. Mesic taxa declined markedly beginning at .apprx. 9000 yr B.P. Between .apprx. 7300 and .apprx. 3500 yr B.P., water levels in the oxbow dropped. Regional forests were dominated by oak and hickory, and mesic taxa became uncommon. Nyssa was extremely common between 2400 and 500 yr B.P.; this probably included black gum in the uplands and both black gum and tupelo gum in wet lowland sites. A regional increase in pine is evident beginning at .apprx. 2400 yr B.P. This pine expansion is eventually associated with decreases in oak, hickory and Nyssa. Aboriginal land use and an increased frequency of fires caused the latter forest changes. An increase in Ambrosia in the uppermost levels marks European settlement. At this time cypress, wetland herbs and shrubs, and Orontium colonized the oxbow, perhaps because of generally higher water levels due to decreased evapotranspiration caused by land clearance.