Vegetation response to a short interval between high-severity wildfires in a mixed-evergreen forest
Donato, D.C., Fontaine, J.B., Robinson, W.D., Kauffman, J.B. and Law, B.E. (2009) Vegetation response to a short interval between high-severity wildfires in a mixed-evergreen forest. Journal of Ecology, 97 (1). pp. 142-154.
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1 Variations in disturbance regime strongly influence ecosystem structure and function. A prominent form of such variation is when multiple high-severity wildfires occur in rapid succession (i.e. short-interval (SI) severe fires, or ‘re-burns’). These events have been proposed as key mechanisms altering successional rates and pathways.
2 We utilized a natural experiment afforded by two overlapping wildfires occurring within a 15-year interval in forests of the Klamath–Siskiyou Mountains, Oregon (USA). We tested for unique effects of a SI fire (15-year interval before 2002 fire) by comparing vegetation communities 2 years post-fire to those following a long-interval (LI) fire (> 100-year interval before 2002 fire) and in mature/old-growth (M/OG) stands (no high-severity fire in > 100-year).
3 Nearly all species found in M/OG stands were present at similar relative abundance in both the LI and SI burns, indicating high community persistence through multiple high-severity fires. However, the SI burn had the highest species richness and total plant cover with additions of disturbance-associated forbs and low shrubs, likely due to a propagule bank of early seral species that developed between fires. Persistence of flora was driven by vegetative sprouting, on-site seed banks, and dispersal from off-site seed sources. Several broadly generalizable plant functional traits (e.g. rapid maturation, long-lived seed banks) were strongly associated with the SI burn.
4 Sprouting capacity of hardwoods and shrubs was unaltered by recurrent fire, but hardwood/shrub biomass was lower in the SI burn because individuals were smaller before the second fire. Conifer regeneration densities were high in both the SI and LI burns (range = 298–6086 and 406–2349 trees ha−1, respectively), reflecting similar availability of seed source and germination substrates.
5 Synthesis. SI severe fires are typically expected to be deleterious to forest flora and development; however, these results indicate that in systems characterized by highly variable natural disturbances (e.g. mixed-severity fire regime), native biota possess functional traits lending resilience to recurrent severe fire. Compound disturbance resulted in a distinct early seral assemblage (i.e. interval-dependent fire effects), thus contributing to the landscape heterogeneity inherent to mixed-severity fire regimes. Process-oriented ecosystem management incorporating variable natural disturbances, including ‘extreme’ events such as SI severe fires, would likely perpetuate a diversity of habitats and successional pathways on the landscape.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Environmental Science|
|Copyright:||© 2008 The Authors|
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