|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Differential responses of oak species to acorn masting: an evaluation of the predator satiation hypothesis.
Steele, Michael*,1, Contreras, Tom1, McEuen, Amy1, Sherick, Michael1, Reed, Seth1, Smallwood, Peter2, 1 Wilkes University, Wilkes-Barre, PA2 University of Richmond, Richmond, VA
ABSTRACT- The predator satiation hypothesis suggests that masting evolved in response to seed predators and that seed survival and seedling establishment will only occur during high mast years. Oak species may, however, differ in the conditions required to satiate predators because of specific acorn-hoarding decisions of small mammals. Specifically, small mammals in temperate oak forests are known to selectively disperse and cache acorns of the red oak subgenus (Eythrobalanus) in contrast to acorns from the white oak subgenus (Quercus) which are preferentially eaten. We therefore predicted that oak species would show differential responses to oak masting depending on the degree of synchrony of acorn production across species and subgenera. We hypothesized that caching and recruitment of red oaks will occur in all years of high acorn production and that white oaks should establish only when they mast alone. We tested this prediction by monitoring acorn production and following the fate of tagged acorns (9000/year) at three sites in NE Pennsylvania over four years. As predicted, caching and establishment of northern red oak (Quercus rubra) increased in a year of high red oak and white oak production. White oaks (Quercus alba) failed to mast without red oak in the years of our study and, as predicted, caching for this species was extremely low across all years and sites. We suggest that the conditions necessary for establishment of white oak species are far more limited than for species of red oak. We also argue that an understanding of the behavioral decisions of small mammals may be key to explaining patterns of oak recruitment within temperate forests.
Key words: acorn masting, predator satiation hypothesis, seed dispersal, Quercus