Do Fungal Symbionts of Salt Marsh Plants Affect Interspecies Competition?

Abstract

The effects of arbuscular mycorrhizal fungi (AMF) as salt marsh plant symbionts may have significant effects on landscape scale distribution patterns and plant-related ecosystem functions that are important to estuarine habitats. This work investigates the effects AMF have on Phalaris arundinacea, Deschampsia cespitosa, and Juncus balticus when grown in a common garden experiment. Plants were grown with and without AMF inoculation in both polyculture and monoculture communities and examined for a variety of response variables that represent different competition strategies. Factorial ANOVA analysis revealed a significant three-way interaction among fungal treatment type, community type, and species for chlorophyll fluorescence, which measures plant stress. Plant stress was higher in J. balticus without inoculation than in inoculated conspecifics, especially when grown in the polyculture community. Conversely, plant stress was slightly lower in the invasive grass, P. arundinacea without inoculation when grown in a community compared to the other combinations. Posthoc tests did not detect any major differences between treatments in Deschampsia cespitosa or in monocultures. Graphs of the other measures of response, ones aimed at determining differences in competition, looked very similar across treatments within a species and between polyculture and monoculture, and did not warrant statistical analysis of the effect of inoculation with AMF. This experiment indicates that fungal inoculation may offer stress amelioration through photosynthetic pathway II to Juncus balticus and may have the opposite effect of non-native Phalaris arundinacea. Given that AMF may have species-specific effects, commercial inoculants, which often do not specify the origin of their soil fungi, could be advantageous to restoration plantings in salt marsh habitats when the native species gain more advantage than locally invasive ones. With increased value placed on salt marsh habitat restoration, these findings serve as an important first step towards determining which AMF-species combinations can benefit salt marsh restoration. iii Dedication This text is dedicated to the female scientists that pioneered the access of professional work in this field for my generation. All of your sacrifices, hardships, and oppressions will not be wasted. Thank you for everything you have done. I would like to express my gratitude to Dr. Catherine de Rivera for her role as my advisor, committee chair, and as mentor beginning in 2012 during my undergraduate degree and continuously through my master's degree completion in 2020. You have provided both insight and pragmatism, but I value your dedicated approach to collaborative and thoughtful science most. Working alongside you has changed my life and understandings about learning, teaching, and the contemplation of the natural world.