Évolution de la régénération après la coupe de peuplements récoltés selon différents procédés d'exploitation

Abstract

Between 1982 and 1984, 289 sample plots were established on cutovers distributed across the mixed and the boreal forest zones of Québec. Regeneration surveys before and after clearcutting were used to determine the proportion of regeneration destroyed by four different harvesting systems. Moreover, information on the evolution of the regeneration over the medium term was gathered from surveys realized five and ten years following logging. For all stands combined, harvesting resulted in a reduction of 25 to 40% of the stocking of the regeneration. The lowest decrease in stocking was produced by a feller-forwarder that was more efficient to protect regeneration shorter than 50 cm as compared to harvesting systems using cable skidders. Differences between harvesting systems were no longer apparent after the first five-year-period following logging because establishment of new seedlings was observed in most of the sampled cutovers. The ability of balsam fir to establish under a canopy generally caused an increase of its proportion in the new stands as compared to the original stands. The proportion of hardwood species also tended to increase in comparison to the original stand in such a way that some conifer stands would evolve toward mixed stands if no change in stand composition occurred after the first ten-year period following logging. Natural regeneration of jack pine stands after harvesting seems difficult to obtain since these stands have scarce advance regeneration that is partially destroyed during logging operations. Plantation, fill plantation or seeding could be applied in these stands but harvesting methods providing protection for regeneration should be used in the other stands in order to protect advance regeneration and particularly tall individuals. Key words: clearcutting, advance regeneration, harvesting system, cable skidders, feller-forwarder