Variable corridor thinning - a cost-effective key to provision of multiple ecosystem services from young boreal conifer forests?

The review discusses the potential of mechanized thinning operations with variable corridor patterns as a method to secure multiple ecosystem services. The focus is on young and dense forests, which are increasingly abundant in Northern Europe and a potential source of renewable biomass for the needs of future bioeconomy. Conventional selective (motor-manual) pre-commercial thinning (PCT) without outtake of cut biomass is used as a benchmark to evaluate a new mechanized thinning method: boom corridor thinning (BCT). The paucity of specific studies on the environmental effects of BCT limits systematic and quantitative comparisons. However, information extrapolated from studies on selective or other corridor thinnings suggests that BCT potentiates early outtake of forest biomass for energy or biorefineries while simultaneously maintaining the stand structure's vertical heterogeneity and thereby supporting biodiversity. More experimental evidence is urgently needed to elucidate the detailed environmental consequences of BCT, and especially its effects on biodiversity and carbon balance. The increasing need to evaluate the pros and cons of silvicultural operations against a broad range of ecosystem benefits necessitates a holistic approach and the development of new typologies and indices that better reflect the structural properties of forest stands.