North American Deserts face invasions from non-native grasses that alter fire regimes. Land managers regularly reseed burned landscapes with native seed, but these efforts often fail to restore native communities. Understanding why reseeding efforts fail is vital to the development of future management practices. Rodent granivory is often overlooked as a key factor in post-fire succession. Rodents consume a significant percentage of both Native and Non-native seed and may have preferences that either inhibit native reestablishment or create biotic resistance against invasion. Our study seeks to characterize the effects of rodent granivory through experimentation on plots constructed in the Mojave and Great Basin Deserts . Both sites contained five replicated blocks each having four treatment combinations comprised of two factors (burned, unburned and rodent present, rodents excluded) in a full factorial design. Petri dishes, containing a mix of soil and seeds from one of several native or non-native species, were placed in each plot. Seed loss from each dish was determined over a two-week period in both 2012 and 2013. Rodent trappings were conducted upon completion of the seed fate experiments to assess rodent populations within each plot.
Results/Conclusions
Percent seed consumption rates were similar between burned and unburned plots showing that fire has little effect on rodent seed selection habits. Between plots, where rodents were excluded and where rodents were given access, significant differences in seed consumption were observed for several seed species; this effect was observed for both years in the Mojave Desert, but only during 2012 in the Great Basin Desert. The lack of a rodent effect for the Great Basin Desert in 2013 was likely the result of abnormally low rodent populations observed in the rodent trapping data. These results suggest that rodents play a key role in altering the seedbank when rodent populations are high. In the Great Basin Desert, rodents exhibited no preference for or against native or invasive species. However, in the Mojave, several species proved to be preferred over others, with two keystone perennials, Larrea tridentata and Coleogyne ramosissima, being consumed to a greater degree than other seeds. Development of reseeding techniques that either protect native seed from rodent granivory or that focus reseeding efforts when rodent populations are low, may greatly increase the success of native vegetation following wildfire.