Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Jennifer Krumins

Committee Member

Scott Kight

Committee Member

Dirk Vanderklein

Abstract

This study explored trophic interactions among herbivores, plants, and soil communities. Two experiments were conducted such that the below-ground effects of an above-ground herbivore, as well as the above-ground impacts of soil biota could be examined. The first project investigated the effects of gypsy moth (Lymantria dispar L.) herbivory on soil communities associated with oak trees (Quercus rubra L.). The goal of this study was to compare soil biota from defoliated oak trees with soil communities from undefoliated trees. The abundances of bacteria, bactivorous nematodes, and herbivorous nematodes were compared between a defoliated sampling site and an undefoliated site in Jefferson Township, NJ. Neither the bacterial abundances, nor the abundances of bactivorous and herbivorous nematodes differed between the two sites, suggesting that above-ground herbivory does not have implications for soil biota in this system. A second project examined the effects of soil food webs on above-ground ecosystems using an extensive dataset. More specifically, structural equation modeling was used to determine the extent to which herbivorous nematodes and the microbial loop influence Ammophila arrenaria L. biomass and carbon allocation through changes in nitrogen availability. Analyses indicated that amoebas, a constituent of the microbial loop, and the associated nitrogen mineralization are responsible for a shift to increased shoot biomass over root biomass. Further, the herbivorous nematode Criconema positively affects shoot biomass through mineralization. This suggests that amoebas and Criconema indirectly increase carbon allocation to above-ground plant tissues. Together, these two studies reflect the degree to which above- and below-ground systems are connected in different habitats.

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