Managing Heterogeneous Stands Using a Multiple-Treatment Irregular Shelterwood Method

In eastern Canada, past diameter-limit cutting left a legacy of low-density and heterogeneous hardwood stands. The complex stand structure and variable density hinders the application of uniform treatments for stand regeneration and rehabilitation. This article describes an innovative approach called the “multiple-treatment irregular shelterwood system.” Two variants of the method are presented to achieve extended irregular shelterwood and continuous cover irregular shelterwood. The silvicultural prescription recognizes microstands that are grouped into microtypes based mainly on sapling stocking and tree canopy closure. For each microstand, harvesting of mature trees is allowed if the understory has sufficient stocking of saplings. If not, partial cutting and/or soil scarification is prescribed to promote regeneration. The design of the trail system and the sequence of entries are adapted for each irregular shelterwood variant. Results from two field trials show that this method is operationally feasible. Existing advance regeneration was adequately protected, and favorable microsite conditions were created when sufficient regeneration was lacking. Half of the volume of wood was harvested from test sites with no high grading of species composition or tree quality, while maintaining a high degree of structural heterogeneity.