Abstract Detail

Ecological Section

Antlfinger, Ann [1], Garabrandt, Marjorie [1], Baker, Jennifer [1], Bough, Lisa [1].

Seedling recruitment, survival and distribution in Nebraska populations of American ginseng (Panax quinquefolius).

Nebraska is on the western edge of the range of Panax quinquefolius. We have studied two sites near Omaha, Neale Woods and Andrews, for 18 and 5 years, respectively. The Neale Woods population consists of 14 clusters of plants, in which all individuals were tagged. At Andrews, we counted all plants in nine 1 m x 15 m transects and tagged seedlings. An average of 11.2 ± 7.4 (SD) seedlings/year have been found (0-24/year) in the Neale Woods population. It varies in size from 99-140 plants. About five more seedlings/year were recruited to the Andrews population (16.6 ± 3.5/year). The Andrews population is larger (192-231 plants). Seedlings usually represented less than 10% of the population at both locations. We measured the distance from each seedling to the nearest 2- and 3-prong plant at the Andrews site in 2004. Seedlings were significantly closer to 2-prong (23.3 cm) than to 3-prong plants (44.5 cm) (paired t = 2.91, P =0.0061, df=37). While this result may suggest reduced competition with a larger adult, the density of American ginseng is low. The distribution of distances was significantly skewed to the right and leptokurtic. At Neale Woods, seedlings established in 1987-90 and 1992 have been monitored the longest. These cohorts showed inverse-J survivorship curves. The average 5-year survival proportion was 0.53 ± 0.14 (SD). These data showed that mortality is high in the juvenile stage of American ginseng. However, once established individuals may be long-lived. The fate of seedlings (N=23) from the five cohorts that survived >14 years was determined. Seedlings spent 3.75 years as a 1-prong plant, 4.65 years in the 2-prong stage, 4.48 years as a 3-prong and less than one year as a 4-prong plant. Thus, it may take 8 years before a seedling contributes significantly to the reproduction of the population.