Oshá Harvest Sustainability
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. Oshá (Ligusticum porteri) is one of these plants and its roots are harvested in meadows of high-elevation forests in Colorado, New Mexico and Arizona, and also in Mexico. We studied population structure, root production, and the ability of Oshá to recover from harvest in different environmental contexts at two 10,000 foot elevation sites in southern Colorado with funding both from the US Forest Service and the American Herbal Product Association (AHPA).
We experimentally harvested roots of mature Oshá plants (flowering and large enough to harvest) at four different rates of harvest (0%, 33%, 66% and 100% of mature plants). Our results indicate that low rates of harvest (33% in all cases; up to 66% in others) in these habitats (which included a meadow, a former burned site, and forested site) allow for recovery of Oshá populations over 3 and 5 years at our Colorado field sites. That is, population numbers of harvested plants had increased to the point that there was no statistical difference between the 0% and 33% harvest rate after 3 years in all cases, and for the 66% rate in some cases. More details and figures are in Kindscher et al. 2019. We believe that Oshá recovers from harvest due to sprouting from rhizome fragments inadvertently left in the ground after harvest. In addition, populations increase in size from seedlings and individuals too small to be targeted by harvesters, aided by heavy snowfall which provide dependable soil moisture well into the summer.
Due to management interest by the US Forest Service, we proposed a sustainable harvest plan based on our field results and analysis that would allow for 50% of the mature plants in a population to be harvested once every 10 years. This would provide a rotational harvest scheme based on 10 Oshá populations. Although we were able to show recovery of Oshá within 5 years in most sites, we are conservative in our recommendation by allowing a longer 10-year recovery period following harvest. The additional time would also allow root mass to increase, leading to more productive harvests. This longer time would also allow for variation in weather patterns and climate change which is projected to increase drought in Southwest forest. We expect drier years would slow the population recovery. Furthermore, we did not measure root yield 3 and 5 years after harvest, as we wanted to leave open possibility of monitoring them in the future. We recommend that any harvest plan implemented in the future include careful monitoring of harvested populations so adjustments can be made (Kindscher et al. 2019).
In addition to this field experiment, we have collected data on other stands of Oshá in the Rio Grande, San Juan and Uncompahgre National Forests in Colorado, and observed previously harvested sites in the Carson and Gila National Forests in New Mexico. Regionally, it appears that Oshá populations are prevalent, especially in high-elevation areas of Colorado, which maintain healthy populations of Oshá . At least some of these are in wilderness areas and locations too far from roads for any meaningful commercial harvest, creating important refugia, stands of Oshá that are protected from significant harvest.
Through our work, we have demonstrated that Oshá can be harvested sustainably given proper permitting by the National Forest Service and responsible harvesters, allowing this important medicinal plant to be used for generations to come.
Oshá Publications