| Biocrusts have been shown to affect the ecological conditions in a variety of habitats, involving abiotic mechanisms such as soil moisture retention, nitrogen-rich biomass additions, changing soil physical properties, as well as direct biotic mechanisms such as impeding seedling growth. In coastal dunes, low-lying interdune habitats experience occasional flooding, which promotes the formation of microbial biocrusts. While storm patterns are known to be effective drivers of coastal dune plant community composition, the interaction between microbial communities and vegetation in the context of storm patterns is not well understood. I investigated the role of biocrusts on native coastal dune community, how environmental conditions, particularly storm patterns, affect interactions between crusts and vegetation, as well as how the presence of crusts affects plant-plant interactions.;To explore correlative patterns between biocrusts, plants and abiotic factors in the field, I analyzed a long term dataset of a coastal dune plant community on St George Island, FL. The presence of several plant species was correlated with crust, and included both negative and positive associations. Additionally, I found correlative relationships with crusts and total plant cover, as well as soil moisture; the latter supports previous research in other systems on the effects of crusts on soil characteristics.;To test the effect of crusts on plant species, I conducted a greenhouse experiment that simulated various environmental conditions, including several water and salt treatments, with and without biocrust in a factorial design. Crusts did have an effect on the growth and survival of some of these species, and this effect varied from negative to positive depending on the species. Additionally, I found trends in the data which suggest that crusts may interact with rain and salt, and this interaction may change the effect of crust on plant species in various environmental conditions.;Lastly, I performed a target-neighbor competition experiment using four dominant coastal dune plant species in a full factorial design to test the effect of crusts on plant-plant interactions. I found that the selected species often strongly compete, and these competition interactions vary among species. I also found a significant effect of crust on one species, Schizachyrium maritimum. |
