Context-dependent interactions among organisms and environmental variables may potentially affect larger community and ecosystem dynamics. We are investigating such context-dependent interactions among species in the microbial biocrust - plant community interface of coastal dunes, a critical habitat on many shores worldwide. Biocrusts in a variety of habitats have been shown to affect abiotic environmental conditions through changing soil chemistry, as well as biotic community dynamics, both directly by impeding seedling growth, as well as indirectly through moisture retention and nitrogen-rich biomass additions. 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. We are investigating the role of biocrusts on coastal dune communities, and how environmental conditions, particularly storm patterns, affect interactions between crusts and vegetation.
Results/Conclusions
Preliminary analyses using long-term data from St George Island, FL show a significant correlation between several specific plant species and the abundance of biocrusts, which suggests that these crusts can affect the plant community composition. Likewise, there are changes in the plant community composition, including increasing density and decreasing diversity with increasing crust abundance per plot, which may be due to an increase dominance by single-species with increasing biocrust abundance. We tested these relationships using factorial greenhouse experiments using dominant coastal dune plant species and various storm condition simulations in greenhouse mesocosms. Our results suggest complex, context-dependent interactions that differ between specific plant species, crust presence or absence, and environmental conditions. In particular, our data suggest plant species’ reactions and interactions differ both in the direction and magnitude as a function of their context. These differences in interaction strength and magnitude have the potential to affect overall community dynamics and function.