COS 255-5 - Promoting Conifer Regeneration in Canadian Boreal Forests through Experimental Uniform Shelterwood: The MISA project

Background/Question/Methods

Partial harvest is considered as a promising alternative to clearcutting system to integrate ecological, economical, and social objectives into silvicultural planning. However, partial harvest has not been widely adapted to the Canadian boreal forest yet and needs further evaluation for multidisciplinary research to adopt it to achieve sustainable management goals. The aim of this study is to evaluate the effects of partial harvest on conifer regeneration in natural even-aged black spruce (Picea mariana (Mill.) B.S.P.) stands 18 years after silvicultural intervention. An experimental design with six sites (three densely younger and three sparsely older stands) and silvicultural treatments (clearcut: 100% of basal area removal, seed-tree: 75%, three variants of shelterwood: 50%, unmanaged) was established by Canadian Forest Service in Monts-Valin and North Shore regions of Quebec. We counted and categorized all seedlings by species and height class in each micro-plot and assess a dominant seedling for the growth features (age, height, diameter, reproduction type) and environment (solar radiation, rooting substrate, soil properties). Second, we evaluated water use efficiency of two conifer seedlings (P. mariana, Abies balsamea) by analyzing stable carbon isotope ratio (δ¹³C) in one-year-old 5 cm branch cuttings.

Results/Conclusions

Conifer regeneration in uniform shelterwood systems promoted a high level of seedling density. However, they were less efficient promoting growth. Regeneration density for black spruce was around four times higher than that for balsam fir. Regarding seedling growth and water use efficiency, the two conifers had different responses to treatment, for example, balsam fir performed a better growth with higher water use efficiency and larger diameter in the residual strips, while black spruce was more efficient in the harvest trails. Our results showed that uniform shelterwood systems can be silvicultural alternatives to clearcutting for conifer regeneration by providing appropriate seedbed and intermediate level of disturbances in black spruce boreal forests. This knowledge will be useful to better understand the dynamics and driving factors of regeneration of Canadian boreal forests after partial harvest to build decision making tools to reach the sustainable forest management goals.