PARENT SESSION
Symposium 19: The Role of Plant-Microbe Feedbacks in Plant Invasions
Organized by: K Reinhart and R Callaway
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Oglethorpe Auditorium.
The interaction of native plants and mycorrhizal fungi on plant growth and soil stabilization processes.
Vogelsang, Keith*,1, Bever, James1, 1 Indiana University, Bloomington, IN
ABSTRACT- Native plant communities are increasingly threatened by introduced species, some of which exhibit invasive qualities. Our work with California grassland species suggests that ecological differences exist among herbaceous native and exotic plants, and that these differences ultimately lead to changes in ecosystem function. Specifically, exotic species appear less dependent on arbuscular mycorrhizal fungi than native species. We tested the community and ecosystem consequences of these differences using manipulated mesocosms. These mesocosms were inoculated with soil communities derived from native-dominated sites and then cultured with assemblages of native or exotic host plants. The divergence of the mycorrhizal communities under their respective host communities caused patterns of differential growth in two related indicator species: Gnaphalium californicum, a California native forb; and Carduus pycnocephalus, an invasive exotic thistle. The native indicator grew best with soil microbes cultured with native plant communities, while the exotic indicator grew relatively better with soil microbes cultured with exotic plant communities. Conversely, the exotic indicator was strongly inhibited by soil microbes from native plant communities. These same mycorrhizal communities also influenced the stability of soil macroaggregates, which form due to the interaction of plant roots, mycorrhizal fungi, and other soil microbes. Stable soil aggregates improve water infiltration, are less erodible, and are associated with multiple ecosystem processes. We show that soil aggregate stability is higher in soil cultured with native plant species than in soil cultured with exotic plant species. Using soil microbes from unmanaged native and exotic plant communities, we also find that soil aggregate stability increases more in response to inoculants derived from native communities. Our results suggest an important link exists between patterns of species introductions and below-ground ecosystem processes.
Key words: mycorrhizae, exotic, native, ecosystem