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Vegetation response to burn severity, native grass seeding, and salvage logging.
Morgan, P., M. Moy, C.A. Droske, S.A. Lewis, L.B. Lentile, P.R. Robichaud, A.T. Hudak,
and C.J. Williams. 2015. Vegetation response to burn severity, native grass seeding, and
salvage logging. Fire Ecology 11(2): 31–58.
Keywords: fire effects, mixed conifer forests, plant succession, post-fire rehabilitation, salvage logging
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Abstract:
As the size and extent of wildfires has increased in recent decades, so has the cost and extent of post-fire management,
including seeding and salvage logging. However, we know little about how burn severity, salvage
logging, and post-fire seeding interact to influence vegetation recovery longterm. We sampled understory plant
species richness, diversity, and canopy cover one to six years post fire (2006 to 2009, and 2011) on 72 permanent
plots selected in a stratified random sample to define post-fire vegetation response to burn severity,
post-fire seeding with native grasses, and salvage logging on the 2005 School Fire in eastern Washington.
Understory vegetation responded rapidly post fire due, in part, to ample low intensity rainfall events in the
first post-fire growing season. Vegetation was more diverse with greater plant species richness and diversity
(Shannon-Wiener index) in low and moderate burn severity plots in 2006 (species richness 18; diversity 2.3)
compared to high burn severity plots (species richness 10; diversity 1.8), with species richness on the high severity
plots reaching 19 in the sixth post-fire year, similar to the initial values on the low and moderate burn
severity plots. Plants that commonly resprout from rhizomes, bulbs, and other surviving belowground sources
were abundant post fire, while those establishing from off-site seed sources, including non-native species, were
present but not abundant. Plots seeded with native grass post fire and not salvage logged had the highest canopy
cover of graminoid species: more than 30 % six years after the fire (in 2011), with low forb (15 %) and shrub
(1 %) canopy cover and species richness. For comparison, high severity plots that were not seeded and not
salvage logged had 3 % graminoid cover, 14 % forb cover, and 26 % shrub cover. Plots that had been salvage
logged from one to three years after the fire produced less canopy cover of shrubs and forbs, but three
times more canopy cover of graminoids on the high burn severity plots by 2011. High severity plots that
were salvage logged and not seeded with native grasses had the lowest species richness, diversity, and cover.
Very few non-native species were found, regardless of salvage logging and seeding. Rapid post-fire growth
dominated by native plants of high diversity suggests that this forest’s vegetation and soils are highly resilient
to disturbance. Overall, burn severity and post-fire seeding with native grasses were more influential
than salvage logging on understory plant abundance one to six years after fire.
Moscow FSL publication no. 2015d
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