Abstract Detail

Ecological Section

Gorchov, David L. [1], Peebles-Spencer, Jessica [2].

Do white-tailed deer mediate apparent competition between an invasive shrub and native plants?

In many areas of the eastern United States, white-tailed deer (Odocoileus virginianus) densities are well above historical levels, with negative impacts on native forest plants. Invasive shrubs, including Amur honeysuckle (Lonicera maackii), have also been shown to have negative impacts on native plants in forests in this region. We hypothesize that L. maackii negatively affects native plants via apparent competition, where deer populations increase by feeding on the invasive shrub, resulting in greater herbivory on native plants. Specifically, we hypothesize that the early leaf expansion of L. maackii, along with its high abundance in the landscape, provides deer with nutritious leafy twigs in early spring while native woody plants are leafless. We are testing these hypotheses with a series of studies in southwest Ohio, where deer are abundant and L. maackii is the most prevalent forest shrub.
We have documented significant effects of deer on the forest floor vegetation composition with a 5-year deer exclosure experiment. Percent cover of tree seedlings increased in exclosures, but only in subplots where L. maackii had been removed. A positive effect of L. maackii on deer populations is suggested by Allan et al.’s (2010) finding of greater deer abundance in forests invaded by L. maackii. To quantify the seasonal pattern of deer browse on L. maackii in forest interior, edge, and early successional vegetation, we will census marked branches. We expect this browse to be significant, because the majority of tagged branches experienced deer browse during early winter (P. Guiden, unpubl.). Furthermore, L. maackii cover within the height range where deer browse (0.5 – 1.5 m) was significantly lower in deer access plots than in deer exclosures. These plots initially had equivalent basal areas of L. maackii, suggesting the differences are the consequence of four years of deer browse.
We will quantify the contribution of L. maackii to deer diet, by estimating the mass of L. maackii twigs browsed by deer browse in forest, edge, and early successional habitat, and comparing the total to estimated total consumption by deer based on population estimates (T. Crist, unpubl.). Finally, we will calculate crude protein content of L . maackii twigs before and after leaf expansion from percent nitrogen, and compare these to published values for other browse species.
Our findings for the interaction between L . maackii and deer may apply to other invasive shrubs with extended leaf phenology.

1 - Miami University, Biology, Pearson Hall, Oxford, OH, 45056, USA
2 - Miami University, Biology, 5982 Vereker Drive, Oxford, OH, 45056, USA

Keywords:
Lonicera maackii
invasive species
deer browse
hervivory
deciduous forest.

Presentation Type: Oral Paper:Papers for Sections
Session: 9
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 10:15 AM
Number: 9007
Abstract ID:272
Candidate for Awards:None