Authors:

Tetianna Smith-Drysdale

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About Paper:

Arbuscular Mycorrhizal Fungi (AMF) form symbiotic relationships with plants, providing nutrients like Nitrogen (N) or Phosphorus (P) in exchange for carbon while at times alleviating plant stress from the environment. Plants can regulate AMF colonization in response to soil nutrients or competitive plant interactions, but it is unclear whether facilitative plant interactions or water availability also alter colonization. We tested how AMF colonization in the roots of an invasive grass species, Bromus hordeaceus, changed with the presence of a native legume, Acmispon americanus, and under drought in a greenhouse experiment. We hypothesized that legume presence would reduce AMF colonization in the grass roots, as legumes can increase soil N through symbiotic N fixation, and that drought would increase AMF colonization, reflecting increased dependence on AMF with environmental stress. We measured AMF colonization, plant interactions, and aboveground 291 UNIVERSITY OF OREGON • 2025 UNDERGRADUATE RESEARCH SYMPOSIUM TABLE OF CONTENTS biomass and found that there was no change in AMF colonization with legume presence, possibly because A. americanus had a weakly facilitative to neutral effect on B. hordeaceus. During drought, grass biomass declined but AMF colonization did not change, indicating that mycorrhizal dependence did not increase during drought or stop declines in plant productivity. As AMF can bolster plant success, characterizing changes to colonization in the roots of an invasive grass can help identify mechanisms promoting invasive grass success.

Source:

University of Oregon / 2025

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Co-authors:

Tetianna Smith-Drysdale