PARENT SESSION
Symposium #2: Linking Aboveground and Belowground Interactions: Emerging Perspectives on the Feedbacks Between Plant and Soil Communities.

Organized by: SD Frey, J Lussenhop, and D Porazinska
Monday, August 5. 8:00 AM to 11:30 AM. Turquoise Ballroom, TCC.

Feedbacks between plants and the soil community: a conceptual overview.

Bever, James^*,1, Westover, Kristi², ¹ Indiana University, Bloomington, IN² Winthrop University, Rock Hill, SC

ABSTRACT- The coexistence of competing species may be mediated through interactions with other trophic levels. For plants, many of these trophic interactions occur below ground. The direct effects of soil microorganisms on plant growth are known to be profound. Yet, with the difficulty of monitoring soil organisms, their importance to plant community processes is easily overlooked. In this talk, we outline one conceptual approach to evaluating the role of soil community dynamics in the maintenance of plant species diversity. This approach involves evaluating the feedback on plant growth through host-specific changes in the composition of the soil community. We have used this approach in a North Carolina grassland and have generally found that the presence of a particular plant changes the composition of its soil community and in a manner that decreases the growth rate of that plant species relative to that of a second plant species. In part, this negative feedback on host growth is due to the accumulation of host-specific soil pathogens in the genus Pythium. But these negative feedbacks can also result from shifts in the species composition of mutualistic arbuscular mycorrhizal fungi and rhizosphere bacteria. These negative feedbacks through host-specific changes in the composition of the soil community can directly maintain plant species diversity. Additional work suggests that soil community feedbacks can be more important to plant species coexistence than competition for abiotic nutrients. This illustrates that dynamics occurring within the soil community can play a critical role in plant community processes.

KEY WORDS: feedback, soil community, Plant ecology, maintenance of diversity