PARENT SESSION
Oral Session #22: Mycorrhizae and ecosystem function.
Presiding: A. Tuininga
Monday, August 5. 1:00 PM to 3:45 PM. Grand Ballroom East, Radisson.
Soil nutrients influencing plant/soil community feedback.
Gustafson, Danny*,1, Casper, Brenda1, 1 Department of Biology, Philadelphia, PA
ABSTRACT- Negative feedback between plant / arbuscular mycorrhizal fungi (AMF) species has been documented in at least two grassland communities, however it is unclear how soil nutrient levels could effect these interactions. The objective of this research was to test plant/soil community feedback among three dominant grasses of the eastern serpentine grasslands, where negative feedback has been documented, as a function of soil nutrient levels. A full factorial experiment with three plant species (Andropogon gerardii, Sorghastrum nutans, Schizachyrium scoparium), three soil sources (soil collected from under each host plant species), and two nutrient treatments (13 N:13 P:13 K, control) was conducted in a greenhouse experiment. Each plant species produced more total biomass with nutrients than without, but the occurrence of negative feedback depended on the nutrient treatment. There was a significant three-way interaction (F=24.04, df=17, 164, p<0.0001) among plant, soil, and nutrient treatments. Within the nutrient addition treatment, Andropogon seedlings were significantly (p<0.05) smaller when grown in soil originally collected from under Andropogon than in soil from under either Sorghastrum or Schizachyrium. In the non-nutrient control, Sorghastrum seedlings were significantly smaller (p<0.05) when grown in soil from under Sorghastrum than from under Andropogon or Schizachyrium. Schizachyrium seedlings showed no significant differential plant growth response related to the different sources of soil. Our results suggest that plant/soil community negative feedback can be significantly influenced by the nutrient status of the soil.
KEY WORDS: Negative Feedback, Serpentine Grassland, Matrix Species