Old-growth white spruce and balsam poplar forests of the Peace River Lowlands, Wood Buffalo National Park, Canada: Development, structure, and diversity

Thirty-seven permanent plots were established and sampled during 1993 and 1994 in Timber Berth 408, Peace River Lowlands, of Wood Buffalo National Park. Sites were sampled for vegetation, bird, physical, and structural attributes, The transition from mature to old-growth conditions occurs at different times In balsam poplar and white spruce forests. In lowland balsam poplar forests, old-growth attributes begin to appear after a stand age of approximate to 80 years, and in lowland white spruce, after approximate to 160 years, Both forest types may persist in excess of 300 years, Attributes shared by, and unique to, both lowland balsam poplar and white spruce old-growth are described, The development of log attributes over time follows opposing trends in flood and fire-origin forests. The preferred rooting medium of white spruce shifts from mineral soil early in succession to decaying wood under pre-existing canopies. Log and snag structure, decay, and dynamics are discussed in relation to time, bryophyte and lichen communities, Canopy height and roughness, total tree cover, and snag and tree animal cavities are described; indicator communities of birds are identified, We conclude with a summary of attributes characteristic of boreal riverine old-growth forests.