Abstract Detail

Ecology

Eckert, Scott [1], Morrison, Janet [2].

Juvenile trees in suburban forests: insights from structural equation modeling.

Suburban forests are exceptionally subject to invasion by non-native plant species such as Microstegium vimineum (Japanese stilt-grass), and to excessive herbivory from overabundant deer, making them novel ecosystems. Suburban forests are important communities, as they contain much of the biodiversity across vast regions, provide ecosystem services, and serve as a liaison between nature and the large sector of human society that lives in suburbs. The effects of invasion and deer overpopulation may work together in suburban forests to induce a greater effect than either would separately, following the invasive meltdown theory. Potential effects on native juvenile trees are particularly important because the future of the forest depends on their success. Using results from a factorial experiment across six suburban forests, with the factors of novel invasion by M. vimineum by addition and deer exclusion via fencing, along with a suite of other environmental variables, we did structural equation modeling (SEM) to investigate the drivers of native juvenile tree percent cover in the herb layer. The best model that fit the data (χ² = 2.606 , P = 0.195) explained 40% of the variance in native juvenile tree cover, and included seven paths linking six variables (native juvenile tree cover in 2012 and 2015, years since hunting began, fencing presence or absence, an index of successional stage of each forest, and average M. vimineum cover). Key takeaways from the model are that 1) deer herbivory had two negative, direct paths to tree cover, 2) one negative indirect path, mediated through the initial tree cover, and 3) that M. vimineum cover had a negative effect on native juvenile trees and was not mediated by deer. Two of the paths (one direct and one indirect) connecting deer herbivory and native juvenile tree cover were due to chronic deer herbivory, measured by the time since hunting began, while the third path linking deer herbivory to the tree cover was from the current deer pressure level, measured by the presence/absence of fencing. Our results suggest that conservation of the native tree community in suburban forests will require joint management of deer and invasive plants.

1 - The College of New Jersey, Biology, 2000 Pennington Rd, Ewing, NJ, 08618, USA
2 - The College Of New Jersey, Department Of Biology, P.O. Box 7718, Ewing, NJ, 08628, USA

Keywords:
suburban forest ecology
Invasive
deer
Structural Equation Model
Trees.

Presentation Type: Poster
Session: P, Ecology Section Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEC025
Abstract ID:655
Candidate for Awards:Ecological Section Best Undergraduate Presentation Award