Application of irregular shelterwood systems as an approach to achieve multi-species management in temperate forests
Managing for species mixtures with contrasted ecological requirements can be highly desirable from an economic and ecological perspectives. However, they are challenging to achieve in practice. Based on the premise that a variety of ecological niches can promote a diversity of species, the application of irregular shelterwood systems (ISS) offers a good potential to achieve multi-species management in temperate mixedwood forests.
This talk will first review the three main variants of irregular shelterwood systems used in North America (extended ISS, continuous cover ISS and expanding-gap ISS). Then, results from an experiment implemented in irregular spruce-fir-yellow birch forest in Québec (Canada) will be presented. This study assesses irregular shelterwood scenarios (extended and continuous cover ISS), inspired by spruce budworm (Choristoneura fumiferana)-driven natural dynamics, as alternative to clearcutting and regular shelterwood cutting.
As expected, shelterwood scenarios diversified light and seedbed conditions compared to the uncut control, but only the continuous cover ISS successfully established a new cohort made of the three target species (Picea rubens, Abies balsamea and Betula alleghaniensis) after 5 years. This result is mainly explained by a lower harvest intensity (37%) that could promote spruce and fir regeneration, while maintaining hardwood and shrub competition at an acceptable level. Conifers poorly regenerated in clearcuts because of heavy competition. Overall, continuous cover ISS could achieve the best compositional and structural objectives.