PARENT SESSION
Poster Session 11: Disturbance Ecology
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Tree-ring reconstruction of forest tent caterpillar outbreaks in the Duck Mountain Provincial Forest, Manitoba.
Sutton, Alanna*,1, 2, Tardif, Jacques1, 1 Centre for Forest Interdisciplinary Research (C-FIR), University of Winnipeg, Winnipeg, Manitoba, Canada2 University of Manitoba, Winnipeg, Manitoba, Canada
ABSTRACT- A dendrochronological reconstruction of forest tent caterpillar (Malacosoma disstria Hubner) outbreaks was conducted in the Duck Mountain Provincial Forest in western Manitoba. Trembling aspen (Populus tremuloides Michx.), balsam poplar (Populus balsamifera L.) and paper birch (Betula papyrifera Marsh.) tree-ring chronologies were used to identify periods of forest tent caterpillar outbreaks from approximately 1800 to 2002. In addition, the spatiotemporal dynamics of the major forest tent caterpillar outbreaks were reconstructed and outbreak characteristics were compared among four stand types and two age classes. The presence of white rings, in conjunction with periods of growth suppression was used to identify three important periods of forest tent caterpillar outbreaks, from 1939 to 1948, 1961 to 1965 and 1982 to 1985, with an additional large-scale outbreak suspected during the 1870s. Smaller outbreaks are also suspected prior to 1800, during the 1950s, the 1970s and during the early and late 1990s. A period with no apparent outbreaks was observed from approximately 1906 to 1936. Observations of the spatial dynamics indicate that the major outbreaks of the 20th century started in the north and spread into the DMPF at different rates. The prolonged 1940s outbreak spread slowly whereas the 1960s outbreak spread quickly following a year of extreme drought. The outbreak of the 1980s was also short, but did not reach widespread proportions. Analysis by stand types indicated that during the dry outbreak of the 1960s, mixed trembling aspen/ jack pine (Pinus banksiana Lamb.) stands registered stronger growth suppression and produced more white rings. Younger sites were found to have higher average growth suppression during the 1980 outbreak.
Key words: Populus tremuloides Michx., Malacosoma disstria Hubner, Insect outbreaks, White rings