Abstract Detail

Interactions of White-Tailed Deer and Invasive Plants in Forests of Eastern North America

Morrison, Janet [1].

Herb layer response to deer exclusion and staged plant invasion within suburban forests.

Fragmented, suburban forests harbor a large proportion of biodiversity across large regions, provide ecosystem services, and offer a connection to nature for many people. Due to their proximity to human communities and little hunting or predation, they are particularly influenced by the dual phenomena of overabundant deer and invasion by many non-native plant species. Understanding the relative importance of these two factors’ effects on suburban forests would inform management and increase our basic ecological knowledge of these understudied ecosystems. We have established a well-replicated experiment combining staged invasions (or not) of Microstegium vimineum (Japanese stiltgrass) with presence or exclusion of deer (with fences), across six forests in a suburban region of New Jersey (224 16 m² plots, established Spring 2013). We are using structural equation modeling (SEM) to analyze the direct and indirect effects of deer, Microstegium, the existing non-native plant community, and other variables on the native herb layer plant community; we aim to understand the forest variables as an interconnected system. The best-fit SEM explained 53% and 59%, respectively, of variation in the spring 2015 native herbaceous and woody percent covers. No paths from Microstegium percent cover to any other variable were significant, even though its average per-plot cover over three years varied from 0-53%. In contrast, chronic deer pressure, measured on a forest basis as –[years of hunting], had a significant, strongly negative influence on the pre-treatment (2012) percent covers of both herbaceous and woody native herb layer plants, which themselves strongly predicted the 2015 values. Exclusion of deer by fencing had additional significant, but positive, effects on the 2015 values, with a greater path coefficient for the herbaceous natives than for the woody natives. The negative influence of chronic deer pressure (but not the positive influence of fencing) extended to percent covers of non-native woody plants in both the shrub and herb layers. In turn, non-natives had negative direct and indirect effects on the 2015 native values. The other major influence (positive) on the natives was the forest’s successional stage, measured as the percent of canopy Importance Value composed of shade tolerant species. Plot-level sunlight and soil moisture variables provided no significant paths. In the first two years of the experiment, deer, the existing non-native woody community, and the forest’s age were the major factors influencing the native herb layer, while novel invasion by Microstegium has had no effect so far.

1 - The College Of New Jersey, Department Of Biology, P.O. Box 7718, Ewing, NJ, 08628, USA

Keywords:
suburban forest ecology
Microstegium
white-tailed deer.

Presentation Type: Colloquium Presentations
Session: C1, Interactions of white-tailed deer and invasive plants in forests of eastern North America
Location: Chatham Ballroom - C/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 2:30 PM
Number: C1004
Abstract ID:423
Candidate for Awards:None