In Great Lakes sand dunes, the dominant dune-building grass is Ammophila breviligulata, which stabilizes mobile sand and initiates the dune-building process. Belowground organisms, especially arbuscular mycorrhizal fungi (AMF) and soil nematodes, associate with the roots of Ammophila and are known to be critical drivers of plant community change in these primary successional systems. In particular, plant-parasitic nematodes can contribute to the dieback of Ammophila, allowing other later-successional species to colonize. AMF are also important for succession, allowing plants to establish in low-nutrient dune soils and slowing Ammophila dieback. Invasion by exotic plants may be associated with shifts in belowground communities, potentially altering plant-soil interactions and successional dynamics. A recent invader in the Great Lakes sand dunes is Leymus arenarius, a dune-building grass native to Europe. This exotic plant has established on dunes along the Lake Michigan coastline. In 2014 and 2015, we conducted field surveys across seven sites in Michigan to assess soil nematode community composition and AMF root colonization associated with the native Ammophila and exotic Leymus plant species.
Results/Conclusions
Our results showed that the native Ammophila and exotic Leymus have similar levels of AMF root colonization (~20%), indicating that both species are likely benefiting from association with AMF. There were significant changes in the soil nematode communities, with Leymus being associated with more bacterivorous nematodes. Leymus plots also had higher nematode enrichment index values, indicating increased soil nutrient enrichment associated with Leymus invasion, possibly due to increased root growth and decomposition of this species. While there were no substantial differences in the abundances of plant-parasitic and predatory nematodes associated with the two plant species, there were differences in the composition of these nematode feeding guilds. Collectively, these results indicate that invasion by Leymus is associated with changes to the soil nematode community, which could have the potential to feed back onto the plant community, altering dune successional dynamics.