Vegetation development of boreal riparian plant communities after flooding, fire, and logging, Peace River, Canada

In this study we compare and contrast vegetation development following natural and logging disturbances in a major boreal river valley. Permanent sample plots and releves were established and sampled for vegetation and landscape attributes in June and July of 1993 and 1994 in the Peace River Lowlands, Wood Buffalo National Park, Canada. In the Peace River Lowlands, primary succession is a flood-origin process. Secondary succession may be either autogenic through gap dynamics mediated by nursery logs, buried wood, and suckering, or allogenic, following fire or logging. Flood origin accounts for 72% and fire origin for 29% of the undisturbed forests. From 1951–1995, 24% of the forest land burned, yielding a fire return interval of 186 years. Forest successional trajectories are set soon after flood, logging, or fire, with little evidence of gradual replacement of one forest type by another. Vegetation composition and relative species abundance are strongly correlated with living moss depth, moss-lichen total cover, total tree cover, herb cover, and canopy height. Species with high indicator value are Hylocomium splendens, Picea glauca, Pyrola chlorantha, Equisetum pratense, and Epilobium angustifolium. Strong correlations exist between white spruce tree density and canopy height, total tree cover and canopy height, total tree cover and basal area per hectare, basal area and canopy height, and between canopy height and surface age. Clearcuts are initially dominated by rose-raspberry followed by balsam poplar (with lesser amounts of Alaska birch and aspen). After logging, temporal changes in composition and dominance occur more rapidly than during natural succession. There is no evidence of post-logging convergence toward the original white spruce and mixedwood forests; a long-term deciduous disclimax is predicted. Vegetation associations, successional pathways, landscape relationships, and ecological benchmarks are identified.