PS 32-31
Desert seedling survival: The interacting effects of fire and small mammals
Invasive exotic grasses are increasing the frequency and size of wildfire in North American deserts resulting in alterations to the vegetation and wildlife communities in these regions. Desert small mammals impact the plant community via granivory, folivory, and seed dispersal. Small mammals may vary in their abundance and diversity between burned and unburned desert regions and thus their impact to the plant community could be altered by a changing fire regime. To better understand how desert wildfire may alter small mammal-plant interactions, we examined the influence of small mammal folivory on seedling survival in experimental plots in the Mojave and Great Basin Deserts. We used a randomized complete block experimental design (with five replicate blocks in each desert) to examine the interactive effects of small mammals (present vs. absent) and fire (burned vs. unburned). Greenhouse grown seedlings of 14-15 common species were transplanted into the four treatments of each block and survival was monitored daily. Data were analyzed using Cox proportional hazards models; top models were selected based on AIC values for each dataset (Mojave 2012, Great Basin 2012, Mojave 2013, and Great Basin 2013).
Results/Conclusions
The best model to describe seedling survival for each dataset included the three-way interaction of small mammals, plant species, and fire. There was an interaction of small mammals and fire in the Great Basin in 2012 and in the Mojave in 2013. In both cases survival was higher in the burned plots with small mammals than the unburned plots with small mammals indicating that the impact of small mammals on seedling survival can differ between burned and unburned regions. Small mammals had a negative effect on seedling survival in both years in both deserts. Desert seedling survival is heavily influenced by small mammals and this impact can differ between burned and unburned regions and vary across plant species. In regions impacted by exotic grass invasion and altered fire regimes, small mammal folivory may have a strong influence on the recovery of the plant community. Because the small mammal community is altered by fire, the resulting impact on the recovering plant community is likely altered as well.