James Amon (Committee Member), Don Cipollini (Advisor), James Runkle (Committee Member)
Master of Science (MS)
Plants alter soil characteristics in many ways causing changes in their subsequent growth resulting in either positive or negative feedback on their own fitness. Plants in their native ranges typically experience negative feedback from natural enemies, while feedback is often positive in invaded ranges where they escape enemies, experience new beneficial mutualisms, or bring with them a novel biochemical weapon. I conducted a fully factorial greenhouse experiment to examine plant-soil feedback in the invasive shrub Lonicera maackii and whether or not positive feedback may contribute to its successful invasion in southern Ohio. I also investigated whether the sign and strength of the feedback changed across two distinct soil types, and whether effects were due to shifts in biotic or abiotic soil traits by analyzing soil properties, phenolic content and microbial communities. I compared L. maackii's response to the related native shrub, Diervilla lonicera, using their conditioned soils along with soil conditioned by an unrelated native tree, Fraxinus pennsylvanica. I hypothesized that L. maackii would experience positive feedback overall in both soil types. L. maackii showed positive feedback in Shawnee soils, but neutral to negative feedback in Wright State soils. Growth of L. maackii decreased and positive feedback was eliminated with sterilization in Shawnee soil which may indicate that it had benefitted from mutualisms that were destroyed by sterilization. In Wright State soil, sterilization significantly increased growth, suggesting L. maackii had been released from pathogenic organisms found in live soils. Despite this, feedback became even more negative with sterilization in Wright State soil which may be a sign that its own phytochemicals hinder its growth in the absence of biotic symbioses. Lonicera maackii performed similarly in its own soils and in those of F. pennsylvanica and D. lonicera, regardless of soil type. Our findings also suggest native species are controlled by negative feedbacks in their own soils. Diervilla lonicera displayed negative feedback overall in its own unsterilized soil regardless of soil type, but sterilization eliminated or reversed feedback relationships. Growth of Diervilla lonicera varied little in soils conditioned by L. maackii and F. pennsylvanica in both soil types. Our results indicate that both soil type and soil microorganisms play a large role in plant-soil feedback, yet feedback in L. maackii is dependent on soil type. Our evidence reveals that sign and strength of feedback can vary with soil source. This is the first study to examine plant-soil feedback in L. maackii, one of the most important invaders in Ohio uplands.
Department or Program
Department of Biological Sciences
Year Degree Awarded
Copyright 2012, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.