Clearcutting and high severity wildfire have comparable effects on growth of direct-seeded interior Douglas-fir

The degree to which harvesting can achieve comparable beneficial effects to wildfire on seedling establishment is a key factor in understanding regeneration dynamics in dry interior forest ecosystems. We compared the capacity of harvesting versus wildfire to support establishment of directly-seeded interior Douglas-fir over a three-year period in the interior Douglas-fir biogeoclimatic zone of British Columbia. The mixed-severity McLure Fire of August 2003 affected over 26,000 hectares in the central British Columbia, Canada. Within the fire-affected area, we assessed growth performance in five disturbance types: High Severity Burn, Low Severity Burn, Clearcut, Screefed Clearcut, and Undisturbed Forest. Seedlings in the High Severity Burn had the significantly greater shoot biomass and root biomass than those in the Low Severity Burn and Undisturbed Forest in the first year. Additionally, seedlings in the High Severity Burn had significantly higher foliar N and P content than those in both clearcut treatments in year one. Foliar nitrogen concentrations remained above critical deficiency levels (1.4%) in both clearcut treatments and the High Severity Burn treatment in all three years. Overall, seedling growth performance in Screefed Clearcut was the most comparable with High Severity Burn treatment, indicating the potential for harvesting with site preparation to produce comparable effects to wildfire on aspects of seedling establishment, particularly growth and nutrition.