Experimental harvest and regrowth in Appalachian black cohosh (Actaea racemosa, Ranunculaceae) populations: Implications for sustainable management of a medicinal forest herb

摘要

A broad range of understory forest herbs are harvested for medicinal properties, particularly from species-rich forests of the central and southern Appalachian Mountains. Many species have been collected and used for centuries with little understanding of harvest impacts, some with resulting population declines. Species valued for belowground components, such as Actaea racemosa L. (black cohosh), appear particularly vulnerable to harvest impacts. Between 2005 and 2011, we conducted experimental harvests on natural A. racemosa populations in central Appalachian oak (Quercus L.) forests. Responses were examined during 3 yr of moderate (33% plant removal) and intensive (66% removal) harvest treatments and up to 3 yr of regrowth, to simulate local harvesting practices and assess recovery potential. After 2 yr of moderate harvests, aboveground growth remained similar to controls. However, after 3 yr of moderate harvests or 2 yr of intensive harvests, significant declines were evident. After our third harvest year, leaf area and stem density were 65-80% lower in moderate harvest plots and 80-90% lower in intensive harvest plots, compared with controls. These differences persisted for at least 2 yr after harvests treatments ended. Curve-fitting models suggested recovery of leaf area and mean plant height to preharvest levels after 4-7 yr without further plant removal. In contrast, stem density showed little to no increase during our study period, and model projections suggested declines, rather than recovery. Thus, although individual growth metrics suggested that limited harvesting may be sustainable, results for stem density indicated little new recruitment into the population and concern for long-term population persistence. Forest herbs harvested for belowground components create particular challenges for sustainable management. Our concerns for A. racemosa are applicable to other economically important forest perennials in our region and worldwide and emphasize the need for continued study and monitoring to maintain viable populations and associated natural systems.