Effects of abiotic stressors and soil microbiota on the zonation of coastal dune plants
Plant species abundance and distribution vary with distance from the shore on coastal sand dunes. Also, differences in soil community composition, as well as gradients of physical stress exist from the shoreline landward. While previous research has mainly focused on one or few of these abiotic and biotic effects on coastal plant communities, they have not definitively explained distribution in terms of these effects, nor have they been presented in realistic combinations of treatments. Therefore, the aim of this study was to illuminate the relationship between coastal dune plants and both the abiotic, as well as biotic aspects of their environment. I exposed seedlings of four key dune plant species to individual tests varying temperature, light, nutrient access, salt spray, soil salinity, and burial, as well as suites of treatments combining those stressors simulating microclimates at both the frontal dune zone and the dune back and flat. Additionally, each species was grown in soils inoculated with either sterile soil, soil from each species’ commonly occurring zone or soils from zones where the target plants were not commonly found.
For individual tests, Rosa rugosa, Myrica pensylvanica, and Ammophila breviligulata accumulated higher biomass when exposed to spray consisting of both half strength seawater salt spray and distilled water as opposed to full strength sea salt spray, while Artemisia campestris did not vary among the three treatments. All species accumulated less biomass when grown in elevated soil salinities as opposed to 0 percent seawater. All species accumulated relatively higher biomass with relatively higher access to nutrients. There was no difference between light and temperature conditions, and only Ammophila showed better growth with relatively larger burial amounts, while the remaining species showed no difference. For treatment suites, both Rosa and Myrica showed less growth under the frontal dune combination, while Ammophila and Artemisia did not differ in biomass between aggregate conditions. Finally, soil microbiota showed a positive influence on all species’ growth, as incubation in sterilized and uninoculated soil revealed lower biomass of all four species. This study revealed that both abiotic and biotic forces significantly influence seedling growth, both individually and in combination. In particular, salt exposure and zone-specific soil community presence drive establishment, and, presumably, coastal plant distribution.