Abstract

Panax quinquefolius L. (American ginseng) is a rare but commercially important herb found in shady forests in eastern North America. In addition to the negative effects of overharvesting (decreasing population size and loss of genetic diversity, among others), P. quinquefolius faces threats from invasive species such as Microstegium vimineum (Trin.) A. Camus (Japanese stiltgrass), a non-native grass that can grow in high densities in low-light environments. The aim of this study was to examine potential competitive effects of increasing M. vimineum densities, focusing on seedling mortality and growth rates of P. quinquefolius seedlings. Commercially-grown P. quinquefolius seedlings were planted in pots with five different densities of M. vimineum, and were censused once per week. Soil samples were collected and analyzed before and after treatments. After 12 weeks, the plants were harvested and dried, biomass of each species was weighed, and P. quinquefolius leaf area was measured. Although P. quinquefolius root and shoot biomass were significantly higher in low-density treatments, there were no significant differences between high-density treatments and control pots. In addition, survivorship decreased in high-density treatments. Soil nutrients also showed significant differences between pre- and post-treatment analysis, indicating soil-altering abilities in M. vimineum. These data point to a possible competitive effect of M. vimineum on P. quinquefolius, though more data and larger sample sizes are needed to confirm this relationship.

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