Impact of logging on the structure of pre-industrial forests in south-eastern Canada
More than 100 years of timber production in the Lower St. Lawrence region of eastern Canada have modified the structure and composition of forests. During the 20th century, old uneven-aged and conifer-dominated forest communities were progressively replaced by young shade-intolerant stands. However, precise evaluations of forest structural changes are still lacking, due to the almost complete disappearance of natural forest stands that could serve as a reference state. The objective of this study is to reconstruct the structure of a preindustrial forest landscape from a detailed survey conducted by the Price Brothers Company between 1928 and 1931. Tree stems were then tallied by diameter and species in several thousand 0.1 ha plots systematically distributed. A systematic re-sampling of 535 of these plots was conducted in the summers of 2012 and 2013 over an area covering 1700 km2 south of Rimouski. Data of these 535 re-sampled plots were compared between the two periods (1928-1930 and 2012-2013)
Between 1930 and 2013, the total basal area (all species combined) and the total stem density increased. On a species basis, results show that although the frequency of occurrence of conifers (Abies balsamea, Picea sp. and Thuja occidentalis) decreased, their basal area and density increased. Maple and poplar species showed the reverse trend with an increase in their frequency of occurrence. Maple basal area and density increased, while they decreased for poplar. The frequency of occurrence and the basal area of White birch and Yellow birch decreased, while their density increased. We conclude that although the forest landscape is composed of the same species throughout the twentieth century, the forest structure has been altered in terms of basal area and stem density.