Document: MAR-3-40-8
Population dynamics of Tamarack (Larix laricina (Du Roi) K. Koch) growing in wetlands from the southwestern Quebec boreal forest.
GIRARDIN, M.P.* 1, J.TARDIF 2 and Y.BERGERON 1
Universite du Quebec a Montreal, Montreal, Quebec H3C 3P8 Canada 1
University of Winnipeg, Winnipeg, Manitoba R3B 2E9 Canada 2
Abstract:
Number of studies have shown the effect of water level and water flow on the distribution of white cedar (Thuya occidentalis), black spruce (Picea mariana) and tamarack (Larix laricina) in wetland sites. The purpose of this study is to demonstrate that periodic flooding and larch sawfly outbreaks are the major factors controlling tamarack stand dynamics. Four stands surrounding Lake Duparquet were chosen for this study. Sampling of the vegetation was made using the transect method and species-environment relations were analyzed using canonical correspondence analysis. Population dynamics were studied in 20 by 20m plots distributed along the same transects. Radial growth and both age and diameter were analyzed. First, ordination results showed that elevation and tree cover were the dominant factors related to species distribution. Preliminary analysis of the tamarack age and diameter showed the existence of different structures along the elevation gradient. The presence of these structures may be attributed to restricted regeneration: 1) in lower sites because of the longer flooding periods, and 2) on higher sites because of competition with Picea mariana and Thuya occidentalis. Thus, tamarack would be more adapted to intermediary sites where seedling survival is maximal. As for the dendrochronological analysis, it has revealed main larch sawfly outbreaks in 1895-1912 and 1958-1961. The larch sawfly outbreaks, by reducing the tree cover and the effect of competition for light, may increase regeneration survival.
Keywords: Boreal forest, Dendrochronology, Larix laricina, Ordination, Sawfly, Wetland
This abstract is being presented at: 3:30 PM in session:
HERBIVORE EFFECTS ON PLANTS