LB 13-164 - Effects of abiotic stressors and soil microbiota on the zonation of coastal dune plants

Background/Question/Methods:

Plants communities on sand dunes occur in predictable patterns with distance from shore, while severity of abiotic stress increases with proximity to shore. Previous work has focused on manipulating one or two environmental factors in determining why these patterns exist. However, the dune environment is a collection of stress filters and biological interactions, including plant interaction with resident soil communities resulting in observed adult zonation. This study aimed to understand how abiotic and biotic factors, individual and in combination, drive plant distributions on dunes in order to potentially contribute to conservation and management efforts. Four key species representative of dune communities and distribution zones of coastal Massachusetts were chosen. To identify the most significant physical effect on seedling growth, individual abiotic factors were tested against discrete trials of graded environmental stressors of salt exposure, sand burial, nutrient depletion, and light exposure. Variations of treatments simulated factor severity as seen in each dune zone. To assess combinations of abiotic effects, seedlings were simultaneously subjected to realistic combinations of the above four treatments. Finally to determine the effect of soil communities on growth, soil was collected from each zone and used to inoculate sterile soil in which seedlings were growing.

Results/Conclusions:

We found that seedlings subjected to relatively higher amounts of either salt or burial had the lowest survival, biomass accumulation and leaf number and grew better with more light and nutrients. As predicted, most species grew best in treatments corresponding to their native zone. Seedlings responded differentially depending on plant species, native dune zone, and inoculation soil source. For instance dune grass, which dominates the dune front, grew less in soil inoculated with shrub-dominated back dune soil, and northern bayberry, a shrub native to the dune back grew twice as well in dune back soil than dune front soil showing that microbial communities play considerable roles in dune plant establishment, as does the interplay between both aboveground and belowground effects.