Forest succession over a 20-year period following clearcutting in balsam fir-yellow birch ecosystems of eastern Québec, Canada

Abstract Vegetation development over a 20-year period following clearcutting in balsam fir (Abies balsamea (L.) Mill.)-yellow birch (Betula alleghaniensis Britt.) ecosystems was examined in a study area located in eastern Quebec, Canada. Vegetation, physiographic and soil data were collected in 10 mature ecosystems and in 30 ecosystems harvested 5 years ago (10), 10 years ago (10), or 20 years ago (10). The 40 ecosystems had similar physiographic and soil characteristics. They were typically located on mesic sites situated on ground moraines thicker than 50 cm. Following harvesting, sites were invaded by competing species. Mountain maple (Acer spicatum Lamb.) was the most important competing species. Twenty years after logging, it fully occupied the sites with 7040 stems ha−1 (diameter at breast height ≥ 1 cm). Its regeneration stocking reached 88% with a density of 22775 stems ha−1. Wild red raspberry (Rubus idaeus L. var. strigosus (Michx.)) and fireweed (Epilobium angustifolium L.) were abundant during a 10-year period after logging, but disappeared almost completely afterwards. The abundance of competing species has considerably reduced site production for a period of 20 years and will probably continue to do so for 20 to 30 more years. The proportion of commercial deciduous species increased from 36% of the total number of stems (diameter at breast height ≥ 1 cm) in mature stands to 89% in stands harvested 20 years ago. Balsam fir and white spruce (Picea glauca (Moench) Voss) advanced regeneration was considerably reduced. Stocking of these species went down from 76% in mature stands to only 27% in 20-year-old stands. As a result, it is unlikely that the harvested areas will naturally evolve toward the original climax balsam fir-yellow birch forest type in the foreseeable future.