Date on Master's Thesis/Doctoral Dissertation
Committee Co-Chair (if applicable)
exotic species; primary succession; sand dunes; soil nematodes
Exotic plants can alter the structure and function of native communities both above- and belowground, which is particularly important in primary successional sand dune ecosystems where plant-soil interactions are critical drivers of successional dynamics. In Great Lakes sand dunes, the native foundation grass Ammophila breviligulata dominates early in succession until an accumulation of detrimental soil organisms causes its die-back of the grasses. Die-back of this native foundation species can be slowed by mutualistic interactions between plants and mycorrhizal fungi. Changes to the plant community resulting from invasion, and subsequent effects on the soil community have the potential to disrupt the successional dynamics of dune systems. Leymus arenarius is a dune-building grass native to northern European sand dunes, and is currently invading Great Lakes dunes. This dissertation examines the effects of L. arenarius invasion on soil community structure, multi-trophic interactions within the soil, and plant community development. In a greenhouse study manipulating the presence/absence of soil organisms, I found evidence of altered multi-trophic interactions. Specifically, arbuscular mycorrhizal fungi provided greater protection from plant-parasitic nematodes to L. arenarius, resulting in weaker biomass reductions relative to A. breviligulata. In a field survey, I found that L. arenarius had little effect on the structure of soil nematode communities and soil bacterial functional diversity relative to uninvaded areas. In a growth chamber experiment, I found that direct competitive effects from L. arenarius were generally similar to effects from A. breviligulata, for later successional native species. However, L. arenarius more strongly suppressed growth of secondary invaders, relative to suppression by A. breviligulata. Soil conditioning effects from L. arenarius were present, but were generally weak suggesting that indirect effects of invasion on soil community composition are less important than direct competitive effects. Experimentally-derived differences in multi-trophic interactions between L. arenarius and A. breviligulata suggested that the invasion of L. arenarius into communities dominated by A. breviligulata would result in altered plant-soil interactions. However, the invasion of L. arenarius did not result in large impacts on plant and soil communities. Overall, these results suggest that L. arenarius has relatively high functional similarity to its native counterpart, A. breviligulata.
Reid, Matthew L., "Soil ecology of the exotic dune grass Leymus arenarius." (2018). Electronic Theses and Dissertations. Paper 2995.