Effects of Soil Burn Severity on Post-Fire Tree Recruitment in Boreal Forest |
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Authors: | Jill F Johnstone F Stuart Chapin III |
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Institution: | (1) Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA;(2) Present address: Department of Geography and Environmental Studies, Carleton University, Ottawa, ON, K1S 5B6, Canada;(3) Arts and Science Division, Yukon College, Whitehorse, Yukon Territory, Y1A 5K4, Canada |
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Abstract: | Fire, which is the dominant disturbance in the boreal forest, creates substantial heterogeneity in soil burn severity at patch
and landscape scales. We present results from five field experiments in Yukon Territory, Canada, and Alaska, USA that document
the effects of soil burn severity on the germination and establishment of four common boreal trees: Picea glauca, Picea mariana, Pinus contorta subsp. latifolia, and Populus tremuloides. Burn severity had strong positive effects on seed germination and net seedling establishment after 3 years. Growth of transplanted
seedlings was also significantly higher on severely burned soils. Our data and a synthesis of the literature indicated a consistent,
steep decline in conifer establishment on organic soils at depths greater than 2.5 cm. A meta-analysis of seedling responses
found no difference in the magnitude of severity effects on germination versus net establishment. There were, however, significant
differences in establishment but not germination responses among deciduous trees, spruce, and pine, suggesting that small-seeded
species experience greater mortality on lightly burned, organic soils than large-seeded species. Together, our analyses indicate
that variations in burn severity can influence multiple aspects of forest stand structure, by affecting the density and composition
of tree seedlings that establish after fire. These effects are predicted to be most important in moderately-drained forest
stands, where a high potential variability in soil burn severity is coupled with strong severity effects on tree recruitment. |
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Keywords: | ecosystem structure disturbance regime landscape pattern Picea mariana Picea glauca Pinus contorta Populus tremuloides post-fire regeneration soil organic layer |
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