High-severity fire increases seed predation of non-fir tree species in a California mixed-conifer forest
摘要
High-severity fire activity in western US dry forests has increased in recent decades, with models projecting extensive declines in tree recruitment and tree species diversity for mixed-conifer forests. While burn severity, seed limitation, and precipitation are known filters of post-fire recovery, seed predation by small mammals may further influence regeneration by reducing conifer seed availability. We quantified how seed removal varies with fire severity, salvage logging, and distance into high-severity patches, as well as across conifer species common to mixed-conifer forests.
ResultsWe measured seed removal rates for four conifer species 2 years following a large wildfire. Sugar pine (Pinus lambertiana), ponderosa pine (Pinus ponderosa), and Douglas-fir (Pseudotsuga menziesii) seeds experienced significantly higher removal rates in high-severity areas relative to low-severity areas, while white fir (Abies concolor) removal remained low across all conditions. Removal of non-fir species in salvage-logged sites was intermediate but not significantly different from other overstory conditions, and did not vary with distance from surviving trees. Mice (Peromyscus sp.) were the primary seed predators in high-severity sites. These findings are based on a single season of data with a modest sample size.
ConclusionsFindings indicate that fire severity amplifies underlying foraging preferences against white fir. The positive effects of fire severity on seed removal may help explain prior observations of low overall conifer recruitment and disproportionate white fir dominance following high-severity fire in mixed-conifer forests.