Structure and dynamics of boreal forest stands in the Duck Mountains, Manitoba

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Hamel, Cary
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No single process seems to characterize succession in the boreal forest; accumulating evidence suggests that it is subject to considerable variation resulting in multiple successional pathways. This study was undertaken to elucidate the structure and dynamics of major boreal forest stands in the Duck Mountain Provincial Park and Forest. Detailed tree size and age data were obtained from each of 70 sampled stands located throughout the study area. Our approach involved reconstructing the initial post-fire composition of these stands, and classifying them into five stand types (Trembling Aspen, Balsam Poplar, White Spruce, Jack Pine, and Black Spruce). Successional pathways within these stand types were inferred through the careful examination of major stand dynamic features in 80-130 year old stands. A novel multivariate approach was used to examine the relationship between the initial cohort and the composition of the subsequent advance regeneration cohort. Variation in patterns of regeneration were examined universally and within each stand type. Timing of recruitment and major factors affecting secondary recruitment were also examined. Our results reveal that landscape-scale succession in Duck Mountain does not result in convergence to a single self-perpetuating 'climax' forest community. Historically, many stands burned with sufficient frequency that canopy succession did not occur, resulting in long-term reestablishment of pre-fire canopy composition. In the absence of disturbance, the initial post-fire cohort composition may be maintained by gap dynamic processes. More often, however, recruitment of other species along with regeneration of the initial cohort species results in increased canopy diversity and complexity over time.