archives@tulane.edu / The influence of environment on microbial community structure is of increasing interest, especially in coastal habitats where climate change is rapidly altering the landscape. In this dissertation, I characterize the microbial communities associated with a key wetland species, the baldcypress tree (Taxodium distichum), and examine the relationship between environment, geographic distance, and microbial community composition. In a culture-based study of T. distichum leaf and root endophytes, I found that both salinity and flooding contributed to bacterial and fungal endophytic community composition. Additionally, I report that diversity and endophyte isolation frequency were higher in roots than in leaves, with leaf bacteria being almost negligible. Using 16S Illumina profiling, I found that geographic distance correlated with rhizosphere but not root endosphere bacterial communities and that mean water level, mean salinity, and the volume of woody debris were correlated with both endosphere and rhizosphere bacterial communities of T. distichum. Finally, using salt challenge assays, I isolated five strains of extreme halotolerant endophytes and eleven strains of moderately halotolerant endophytes— a necessary first step towards using endophytes for restoration, or towards understanding the functions of some of these organisms in situ. This dissertation demonstrates a connection between environmental variables, plant symbionts, and a key restoration species and may help in predicting future outcomes of sea level rise for endophytes communities in baldcypress and other wetland plants. / 1 / Elizabeth Kimbrough