Recovery of devil’s club (Oplopanax horridus) after clearcut logging in northwestern British Columbia

Background/Question/Methods

Oplopanax horridus (Sm.) Miq. (devil’s club) is an important plant to First Nations of British Columbia, Canada. More than 34 broad categories of medicinal use and eight categories of spiritual use of devil’s club have been listed by researchers for 38 linguistic groups from across western North America. In northwestern British Columbia, concern was expressed by some First Peoples that ongoing clearcut logging over the last 50 years was destroying the preferred populations of this species. To address these concerns, a preliminary retrospective study evaluated devil’s club recovery in clearcuts of different ages. Sixteen clearcuts ranging in age from 3 to 37 years and one old-growth stand were selected for study. At each site, the basal diameter and height of ten randomly selected devil’s club stems were measured. Observations on vigour, growth form, site attributes and associated vegetation were also noted. Data were analyzed by linear regression and one-way ANOVA to test for the influence of stand age or stand age class on plant attributes. All factors were combined in a stepwise multiple regression analysis to derive the best explanatory model of post-logging stem diameter.

Results/Conclusions

Although devil’s club plants were present on most relatively moist and nutrient rich sites after logging, many showed signs of historical damage or stress, apparently due to ground-based skidding operations, exposure to full sunlight, or slash burning. Those in young (<10 years since disturbance) stands had typically resprouted after damage, but were too small to harvest for traditional uses. Large stems, not significantly different in size from those growing in the preferred old growth harvesting area, were found in the 10-19 year old stands, but the results for all clearcuts over 10 years of age were highly variable. The final stepwise multiple regression analysis confirmed that stand age was the most important determinant of devil’s club stem diameters, with microsite and plant community factors less important. Results suggest that devil’s club does persist after logging and there is a general tendency for stems to increase in size as time passes. It is recommended that logging activities can reduce damage to devil’s club populations if known patches are avoided by ground-based machinery, and if slash piles are left to provide some level of shade.