Effects of arbuscular mycorrhizal fungal infection and common mycelial network formation on invasive plant competition

Understanding the biotic factors influencing invasive plant performance is essential for managing invaded land and preventing further exotic establishment and spread. I studied how competition between both conspecifics and native co-habitants and arbuscular mycorrhizal fungal (AMF) impacted the success of the invasive bunchgrass Brachypodium sylvaticum in early growth stages. I examined whether invasive plants performed and competed differently when grown in soil containing AMF from adjacent invaded and noninvaded ranges in order to determine the contribution of AMF to both monoculture stability and spread of the invasive to noninvaded territory. I also directly manipulated common mycelial network (CMN) formation by AMF to determine hyphal network contribution to competitive interactions. I found that invasive plants performed most poorly (as indicated by decreased chlorophyll content, size and shoot dry mass) in invaded range soil against conspecifics. This could be two-pronged evidence for existing biotic pressure on the invasives to expand into adjacent noninvaded ranges. I also found a negative effect of AMF colonization and invasive plant performance, potentially indicating deleterious plant-soil feedbacks which could help maintain plant biodiversity at a community level. CMN effects were found to be interactive with root competition and directly affected the performance and nutrient status of B. sylvaticum. Although no direct correlations between AMF colonization levels and competition were found, CMN presence contributed significantly to plant growth and nutrient status. Therefore AMF, through infection and CMN formation, may be able to influence invasive plant growth and spread in the field.