PARENT SESSION
Organized Oral Session 32: Forest disturbance regimes in the circumboreal forest zone: Natural variability and implications for forest management and biodiversity conservation
Organizer(s): S Gauthier, T Kuuluvainen, and D Kneeshaw
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 516 C, Level 5, Palais des congrès de Montréal
Wind disturbance patterns in Haida Gwaii (Queen Charlotte Islands), British Columbia.
Pearson, Audrey*,1, Mitchell, Stephen1, Lanquaye, Naa1, 1 University of British Columbia, Vancouver, BC, Canada
ABSTRACT- While natural disturbances are now recognized as templates for ecosystem-based management, there is very baseline information for wind disturbances at the stand- or landscape-level for coastal BC. We used a combination of historical and modern aerial photography, field investigations and modelling techniques to determine landscape pattern of stand-replacing wind disturbances for Haida Gwaii. Sample NTS map sheets comprising 10% of the Islands were chosen to represent the three physiographic regions and a range of exposure to prevailing weather systems. For the sample map sheets, we determined location and size distribution of wind disturbance patches on the available air photo series (1937, 1964, 1979, 2004), groundtruthed the classification of stand-replacing versus gap-phase regeneration events, and determined variation in forest structure between the two disturbance types. There was evidence of one major storm on the 1964 photos for the west coast, but for the remainder of the air photo series and areas, wind disturbance patches were small and isolated. There was a broad range in the number of gapmakers per gap, from 2 to 84, even though areas sampled were considered old-growth forest. A high percentage of the forest canopy was canopy gap relative to closed canopy, indicating wind disturbances are frequent, but do not create large openings. Integration of windthrow mapping with other GIS layers, including numerically modelled wind speeds, has enabled us to fit a logistic regression model for prediction of those locations in the landscape that are most prone to stand-replacing wind disturbance. Historical aerial photography is a valuable tool for constructing environmental baselines such as natural disturbance patterns because in most instances the early photos date before industrial logging became widespread on the BC coast.
Key words: wind disturbances, landscape ecology, forest structure, ecosystem-based management