Paleoecology of central Kentucky since the last glacial maximum

Abstract

Pollen grains and spores, plant macrofossils, and sponge spicules from a 7.2-m sediment core from Jackson Pond dating back to 20,000 yr B.P. are the basis for new interpretations of vegetational, limnological, and climatic changes in central Kentucky. During the full-glacial interval (20,400 to 16,800 yr B.P.) upland vegetation was closed spruce forest with jack pine as a subdominant. Aquatic macrophyte and sponge assemblages indicate that the site was a relatively deep, open pond with low organic productivity. During late-glacial time (16,800 to 11,300 yr B.P.) spruce populations continued to dominate while jack pine declined and sedge increased as the vegetation became a more open, taiga-like boreal woodland. Between 11,300 and 10,000 yr B.P., abundances of spruce and oak pollen oscillated reciprocally, possibly reflecting the Younger Dryas oscillation as boreal taxa underwent a series of declines and increases at the southern limit of their ranges before becoming extirpated and replaced by deciduous forest. In the early Holocene (10,000 to 7300 yr B.P.) a mesic deciduous woodland developed; it was replaced by xeric oak-hickory forest during the middle Holocene between 7300 and 3900 yr B.P. Grass increased after 3900 yr B.P., indicating that the presettlement vegetation mosaic of mixed deciduous forest and prairie (the “Kentucky Barrens”) became established in central Kentucky after the Hypsithermal interval. Sponge spicules increased in number during the Holocene, reflecting reduced water depths in the pond. Sediment infilling, as well as climatic warming and the expansion of fringing shrub thickets, increased nutrient and habitat availability for freshwater sponges.

The 1997 Excavations at the Big Eddy Site (23CE426) in Southwest Missouri

“…Although corroborative data are unavailable for the region, pollen data from sites in the Midwest and eastern Plains show high percentages of herb or nonarboreal pollen, indicative of the expansion of prairie, during the interval of 11,000-9000 B.P. (Bernabo and Webb 1977;Davis 1965;Gruger 1973;McAndrews 1966McAndrews ,1967Wilkins et al 1991;Wright 1976). A similar transition has also been reported for several areas of the southern Great Plains.…”

“…The Younger Dryas event was first defined in Europe, but much data have been accumulating to show that this event may have been global (e.g., Haynes 1991;Wilkins et al 1991). Its North American signatures may be strongest in the maritime Canadian provinces and southern New England (Jouzel et al 1992;Peteet 1992).…”

“…Sections of pollen profiles from many midwestern sites that date to the interval of 11,000-9000 B.P. show high percentages of herb or nonarboreal pollen, indicative of the expansion of prairie (Bernabo and Webb 1977;Davis 1965;McAndrews 1966McAndrews , 1967Wilkins et al 1991;Wright 1976). Thus, this period witnessed the emergence of the so-called Prairie Peninsula (Transeau 1935), although it did not reach its maximum extent until the middle Holocene.…”

Predicting Pleistocene climate from vegetation in North America

“…The Pleistocene Last Glacial Maximum (LGM) period of 18 000 years ago has been widely interpreted as a time of bitter cold in eastern North America when tundra and boreal forest extended hundreds of miles south of the ice sheets and the temperate forest of the East retreated to the southern coastal plain, to Florida, and westward into Texas and Mexico (Davis, 1983(Davis, , 1984Davis and Shaw, 2001;Deevey, 1949;Delcourt, 1984, 1993;Jacobson et al, 1987;Maher et al, 1998;Maxwell and Davis, 1972;Overpeck et al, 1992;Prentice et al, 1991;Ritchie, 1987;Royall et al, 1991;Schoonmaker and Foster, 1991;Tallis, 1991;Watts, 1970Watts, , 1971Watts, , 1973Watts, , 1979Watts, , 1980aWatts and Stuvier, 1980;Webb et al, 1988Webb et al, , 1993Whitehead, 1973;Wilkins et al, 1991). This reconstruction, which may be called the standard model, is commonly presented in textbooks (e.g., Bradley, 1999;Delcourt and Delcourt, 1993;Pielou, 1991;Ritchie, 1987;Tallis, 1991).…”

The Pleistocene biogeography of eastern North America: A nonmigration scenario for deciduous forest

“…Jackson Pond in Kentucky (Wilkins et al, 1991) is a site that should show unequivocal boreal forest, because it is an interior site and is only 100 miles from the ice border. The sediment core taken here is continuous in radiocarbon years back to 20,000 BP.…”