Volume 368, 15 May 2016, Pages 133–139
Highlights
- •
- We manipulated predator distributions through fencing in a longleaf pine savanna.
- •
- After 10 years we compared vegetation in areas with and without predators.
- •
- Woody browse was released and preferred forage was reduced in predator exclosures.
- •
- We found support for the Behaviorally-mediated trophic cascade hypothesis.
- •
- Scared deer help suppress hardwood encroachment in frequently burn pine savannas.
Abstract
Ecologists
increasingly recognize the importance of trait-mediated indirect
interactions and suggest behavioral traits aimed to reduce predation
risk can induce trophic cascades. However, the application of theory
developed in simple experimental systems to complex natural systems has
spurred debate regarding whether predation risk, independent of direct
killing, can structure ecosystems. We examined the effects of
white-tailed deer (Odocoileus virginianus) foraging under the risk of predation by coyotes on oak (Quercus
spp.) regeneration and the abundance of palatable understory species in
a frequently burned longleaf pine savanna. Oaks represent a common but
relatively low quality forage item for deer, and are an important
component of this system because oak encroachment into pine-dominated
uplands can reduce biodiversity. In frequently burned ecosystems oaks
and other fire-impeding species often exist in a demographic fire-trap,
where they sprout following fire but rarely escape into the midstory,
because they are repeatedly top-killed by subsequent fires. Many factor
including herbivory stress can influence the probability of fire
survival for oak saplings. Other Cervids, including elk (Cervus canadensis) and moose (Alces alces)
are known to increase use of woody browse with predation risk because
of selection for brushy areas that offer concealment cover. We
experimentally manipulated predation risk for 10 years, by establishing 4
approximately 40-ha predator exclosures and 4 control plots to test the
effects of predation risk on aspects of the plant community. Reduced
predation risk resulted in increased oak recruitment and decreased
abundance of palatable forage. A density-mediated trophic cascade does
not explain the release of oaks and our results provide support the
behaviorally-mediated trophic cascade hypothesis. We offer evidence that
frequent disturbance can facilitate trophic cascades and that
predator-sensitive foraging can enhance fire suppression of oaks and
influence groundcover composition in longleaf pine savannas.
Keywords
- Canis latrans;
- Coyote;
- Longleaf pine;
- Fire;
- Non-consumptive effects;
- Oak recruitment;
- Odocoileus virginianus;
- Predation risk;
- Prescribed fire;
- Trophic cascade;
- White-tailed deer
Copyright © 2016 Elsevier B.V. All rights reserved.
