Abstract
BackgroundLarge wildfires result in more heterogeneous fire scars than do smaller fires because of differences in landscape context and high variability in burn intensity and severity. Previous research on mammal response to wildfire has often considered all fires as comparable disturbances regardless of size. Here, we explicitly examine whether fire size affects relative abundances of a keystone herbivore, snowshoe hare (Lepus americanus Erxleben, 1777), in regenerating stands of the same age. We surveyed vegetation and fecal pellets of snowshoe hares in nine 13-year-old wildfires, specifically, three fires in three size categories—small (80 to 200 ha), medium (1000 to 5000 ha), and large (>10 000 ha)—and in mature forests in southern British Columbia, Canada.ResultsSnowshoe hare density was low (0.4 hares ha−1), but hares were present at 57% of mature sites. Hares were absent from all areas where small fires had burned and were found in only one medium area post fire (0.2 hares ha−1). Hares were found within the fire scars of all three large burned areas, and with much higher numbers (3.8 hares ha−1) than in the medium fire area or mature forest. Snowshoe hare abundance was highly correlated with the number of sapling trees, especially lodgepole pine (Pinus contorta Douglas ex Loudon). Sapling densities were highly variable, but dense stands of saplings were found only in burn scars from large wildfires.ConclusionsFire size is an important predictor of snowshoe hare relative abundance in areas that are regenerating post fire; fires of different sizes are not comparable disturbances. Specifically, the post-fire heterogeneity after large fires enabled both the highest hare numbers as well as patches with no hares. These results suggest that forest and wildlife managers should protect areas with dense regeneration post fire, as these sites are necessary for hares after large wildfires.
Highlights
Large wildfires result in more heterogeneous fire scars than do smaller fires because of differences in landscape context and high variability in burn intensity and severity
Hare pellet abundance varied with fire size and between burned areas and mature forests (Fig. 1; F3,27 = 3.21, P = 0.038); large burned areas had the highest pellet counts (10.4 ± 13.1 pellets transect−1, X ± 1 standard deviation), followed by mature forest sites (0.8 ± 1.0 pellets transect−1), whereas hare pellets were scarce in medium burned areas (0.3 ± 0.7 pellets transect−1), and absent in small burned areas (0 ± 0 pellets transect−1)
Large wildfires induce high post-fire heterogeneity, and our results suggest that forest and wildlife managers should protect post-fire forest patches that either have legacy forests or dense post-fire regeneration
Summary
Large wildfires result in more heterogeneous fire scars than do smaller fires because of differences in landscape context and high variability in burn intensity and severity. Regeneration after a large fire is less reliant on seed dispersal from the surrounding unburned forest because of the sheer distance between the edge and center (Turner et al 1997; Harvey et al 2016), whereas regeneration after smaller burns is greatly affected by available seedbanks of forest edges because seed dispersal is less distance-limited and there are more living trees remaining (Perera and Buse 2014)
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