Abstract Detail

Ecological Section

Crandall, Raelene [1], Knight, Tiffany [2].

Biotic interactions increase the effectiveness of using fire to control Ailanthus altissima (Simaroubaceae).

Historically, low intensity fires were common across open savannas in North America. In the absence of fire, these habitats were converted to closed-canopy forests with low understory plant diversity. Additionally, fire suppression often facilitates the invasion of exotic species, resulting in their subsequent dominance of native communities. When used as a restoration tool in these ecosystems, fires sometimes successfully reduce the abundance of exotic plants and increase the diversity of native species and other times have no effect or even facilitate additional biological invasions. The effectiveness of reintroducing fire should depend on: (1) response of the exotic species to fire; (2) regulation by enemies (i.e., enemy release hypothesis); and (3) competition with resident species (i.e., biotic resistance hypothesis). Fire likely weakens the effects of both enemies and competitors, thereby giving exotic species the opportunity to quickly regenerate or recruit in the post-fire environment. Thus, we predict that weakened biotic interactions resulting from fire will decrease the effectiveness of using fire for restoration of exotic-invaded habitats. In fire-suppressed oak-hickory forests (Missouri, USA) we determined (1) whether populations of Ailanthus altissima (Simaroubaceae) could be controlled using dormant season prescribed fires; and (2) if the influence of fire was mediated by herbivory and competition with neighboring plants. We manipulated the presence of herbivores by applying a broad-spectrum herbicide, and reduced competitive interactions by clipping all neighbors to ground level. Using integral projection models, we found that fire, in general, increases the population growth rate of A. altissima by increasing seedling recruitment. In fact, the lowest population growth rate is found where fire is absent and biotic interactions are strong. When competition or herbivory are reduced, A. altissima’s population growth rate increases, particularly when fire is present. These results indicate that biotic resistance and the presence of enemies are important for slowing the invasion of A. altissma. Disturbances that weaken biotic interactions, such as fire, should not be used to restore habitats invaded by A. altissima. Response of exotic species to fire, as well as fire’s influence on factors that regulate population dynamics, should be considered before using prescribed fires with the goal of restoring native biodiversity.

1 - Washington University - St. Louis, Department Of Biology And Tyson Research Center, Box 1137, St. Louis, MO, 63130, USA
2 - German Centre for Integrative Biodiversity Research (iDiv) , Halle-Jena-Lepzig, Germany

Keywords:
invasive species
fire
herbivory
competition.

Presentation Type: Oral Paper:Papers for Sections
Session: 9
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:45 AM
Number: 9002
Abstract ID:962
Candidate for Awards:None