Harvesting and Recolonization of Wild Populations of Oshá (Ligusticum porteri) in Southern Colorado

Abstract

Land managers face the challenge of conserving medicinal plants that may be threatened by harvest pressure, often with limited biological information available to inform management decisions. Osha (Ligusticum porteri) is an important medicinal plant whose roots are harvested as an herbal remedy for flu, sore throat, and other illnesses. However, little is known about population structure, root production, or the capacity of osha to recover from harvest in different environmental contexts. We compared osha population structure and root production within a gradient of canopy cover from meadow to forested habitat. We experimentally harvested roots of mature osha plants and recorded osha recolonization of pits created by root harvest. Prior to harvest, the number and percent cover of reproductive plants and the number of flowering stems per plot were higher in the meadow than in forested habitat. Canopy cover had a significant negative relationship to these variables, suggesting that osha populations benefit from increased light availability. Average root weight per plant in meadow plots was three times higher than in forested plots. One year after harvest, the majority of all harvest pits across the canopy cover gradient were recolonized by osha. Our results suggest that osha population structure and root production are significantly influenced by canopy cover, but that plants have a high capacity for post-harvest recolonization under variable light conditions. These results demonstrate the need to account for environmental factors that influence population structure when addressing concerns about the overharvest of wild medicinal plants.