Exposure to fire affects acorn removal by altering consumer preference

Abstract

Prescribed fire has been encouraged as a management tool to increase oak regeneration across the southeastern United States. The least utilized part of the burn window in this region is during fall, but burning in this season with the objective of oak regeneration has been discouraged because of the potential negative consequences on subsequent germination. While exposure to fire decreases acorn viability, acorns cached in recently burned areas increases their survival. By following the fate of unburned acorns added to those areas, previous studies identified post-fire habitat characteristics (e.g., altering vegetation structure, decreased leaf litter, etc.) as a cause of increased acorn establishment success. However, exposing acorns to fire may also contribute to fate of surviving acorns by changing consumer removal rates. We exposed acorns to fire and established cafeteria-style experiments in unburned forests to compare burned and unburned acorn selection and removal rate of eight oak species by caching and non-caching consumers (i.e., predator type). Exposing acorns to fire did not appear to affect selection of oak species but affected overall removal risk for acorns differently by species of consumers. For example, while one important non-caching consumer (white-tailed deer, Odocoileus virginianus) and caching consumer (southern flying squirrel, Glaucomys Volans) showed strong selection of burned acorns, other important consumers in each predator type showed little discrimination or strong selection of unburned acorns (e.g., southern fox squirrel Sciurus niger). Exposure to fire reduced the overall rate of removal of acorns and when an acorn was removed, fire significantly reduced the probability that it would be removed by a caching consumer. Overall, our experiment demonstrates that shifts in consumer removal for exposed acorns may play an important role in the net effects of fall burning on oak regeneration.