Exploring the role of arbuscular mycorrhizal fungi in freshwater wetlands of the tallgrass prairie

Background/Question/Methods

A mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi has been shown to increase plant uptake of mineral nutrients such as phosphorus, nitrogen, potassium, zinc, and iron. Evidence of these and other benefits to plant growth in terrestrial systems far exceed our understanding of the symbiosis in freshwater wetlands environments.  Plants adapted to wetlands ecosystems must cope with a range of water availabilities, rapidly changing soil characteristics, nutrient availabilities, and plant competitors. It is unknown whether AM fungi provide the same level of nutrient acquisition to species in moist and inundated soils as those in dry soils. We hypothesized that symbiotic benefits for freshwater prairie wetland plants would be similar to those observed in terrestrial prairie habitats. Emergent macrophytes selected for the study range from obligate to facultative wetland species and include C₃ and C₄grasses, graminoids, and forbs from the Great Plains. These were established from seed in either unamended prairie soil or sterilized soil and transferred to one of three simulated wetland environments in the greenhouse (well-drained, ephemeral, or permanently saturated). By exploring the growth responses of 47 wetland plant species to mycorrhizal colonization, we can identify individual species growth responses and variation in root colonization.

Results/Conclusions

Over 70 percent of plant species investigated exhibited increased survival when grown in the native prairie soil compared with sterilized soil lacking AM fungi. Aboveground biomass was significantly greater in mycorrhizal treatments than in non-mycorrhizal treatments. However, there was no significant difference in plant biomass among the three water treatments in either fungal treatment. Specific leaf area did not vary significantly among either the water treatments or the fungal treatments. While still under investigation, we predict that percent mycorrhizal root colonization will vary in both fungal and water treatments. Our results suggest that similar to terrestrial systems, the majority of emergent freshwater species respond positively to the presence of AM fungi in the soil and benefit from a symbiotic relationship. Consensus of these relationships with naturally-occurring spatial and temporal changes in plant response will increase our understanding of wetland plant community composition, individual species colonization and survival, and broad-based restoration efforts of freshwater prairie wetlands.