Preindustrial forests in the balsam fir-yellow birch bioclimatic zone in eastern Canada - CANCELLED

Background/Question/Methods In the Lower St-Lawrence region of eastern Quebec (Canada), industrial logging for over a century and modifications in fire regime have transformed profoundly the original forest composition, making it difficult today to develop forest management systems based on natural disturbance regime. Historical vegetation composition provide a reference condition from which we can examine the changes that have occurred to the present. We used detailed and precisely situated descriptions of forest stands in early land survey records (1852-1949) to reconstruct the preindustrial forest composition of an area covering 3451 km². We also used recent forest inventories (1970-2008) to evaluate changes in forest composition since preindustrial time. In total, 8599 ranked timber observations were tallied from 11113 vegetations information found in surveyor’s notes. Two land survey periods were distinguished, 1852-1903 and 1894-1949, based on differences in methodology used by surveyors.

Results/Conclusions The most frequently mentioned taxa were (% 1852-1903; % 1894-1949): spruce (Picea spp.) (20.8%; 19.6%), balsam fir (Abies balsamea) (19.7%; 22.6%), white cedar (Thuja occidentalis) (19.1%; 15.3%), white birch (Betula papyrifera) (12%; 13.9%), yellow birch (Betula alleghaniensis) (10.3%; 12.8%) and sugar maple (Acer saccharum) (6.0%; 6.6%). In comparison, univariate statistical tests indicate that current forest composition has considerably less cedar and spruce and more trembling aspen (Populus tremuloïdes), sugar maple, and fir. For both land survey periods, analyses showed that fir, cedar and sugar maple were dominant taxa, whereas spruce, yellow birch and white birch were more often seen as second, third, or fourth dominant taxa within stands. Through co-occurrence analyses we identified three major recurrent species assemblages for the period 1852-1903: (1) cedar-spruce-fir (2) fir-spruce-white birch-yellow birch (3) sugar maple-yellow birch. The sugar maple group was dominant on hill tops, whereas stands with cedar ranked first were more abundant in the low lands. Forest composition changes since preindustrial time provide guidelines for sustainable forest management in the Lower St-Lawrence region.