Impacts of experimental leaf harvesting on a north American medicinal shrub, Rhododendron groenlandicum

Harvesting of medicinal plants from wild populations is increasing worldwide, however, studies on sustainable harvesting techniques are lacking. In this exploratory study, we investigated the impact of leaf harvesting on Rhododendron groenlandicum (Oeder) Kron & Judd, a North American temperate shrub, used traditionally as a medicinal plant by the Cree Nation. The species is widely distributed, but Crees are worried that commercial harvesting could threaten local plant populations. Our study was conducted near the Cree Nation of Mistissini (James Bay, Northern Quebec). Three leaf harvest regimes were tested in 2008 and 2009: no harvest, all leaves harvested, and only old leaves harvested; each treatment was performed on 30 plants. The harvesting of all leaves had a negative impact on stem elongation after the first harvest, while leaf production and stem radial growth decreased after the second harvest. Two-thirds of the plants also died following the second regime of harvesting all leaves. The harvesting of old leaves had no significant impact on growth, leaf production, or survival of R. groenlandicum, even after 2 years of harvest. These results lead to the conclusion that sustainable harvest of this species is possible, but further study is required to make definite recommendations. Key words: conservation, medicinal plant, sustainability, harvesting simulation, Cree Nation. La recolte de plantes medicinales provient surtout de populations sauvages et peu d'etudes existent sur leur durabilite. Nous examinons ici l'impact de la recolte sur Rhododendron groenlandicum (Oeder) Kron & Judd, un arbuste nord americain utilise par la Nation crie pour ses proprietes medicinales. Cette espece est deja recoltee commercialement au Quebec, ce qui pourrait menacer localement certaines populations : cela inquiete d' ailleurs la Nation crie. L'objectif de cette etude etait d' evaluer l' impact de la defoliation sur des plants de R. groenlandicum situees a proximite de Mistissini (Baie James, Quebec). Trois niveaux de recolte de feuilles ont ete appliques sur 30 plants chacun en 2008 et 2009 : aucune recolte, la recolte de toutes les feuilles et la recolte des vieilles feuilles seulement. Les resultats montrent que recolter toutes les feuilles a un impact negatif sur l' elongation des rameaux apres une seule recolte tandis que la croissance radiale et la production de feuilles diminuent apres deux recoltes consecutives. De plus, une mortalite importante des plants (deux tiers) est survenue apres la deuxieme recolte. La recolte des vieilles feuilles seulement n' a pas d' impact significatif sur la croissance et la survie, meme apres la deuxieme annee. Nos resultats indiquent que la recolte de cette plante serait soutenable, cependant d' autres etudes sont necessaires pour emettre des recommandations. Mots-cles : conservation, plantes medicinales, developpement durable, simulation de recolte, Nation crie. [Traduit par la Redaction]
Introduction Medicinal plants are gaining popularity in industrial societies as alternative medicine, and their sales are increasing (Cavaliere et al. 2010). This accelerating interest may lead to overharvesting, which in [...]