PARENT SESSION
Poster Session 30: Soil Ecology.
Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Plant legacy effects on rhizosphere microbial community structure.
Maul, Jude*,1, Drinkwater, Laurie1, 1 Cornell University, Ithaca, NY
ABSTRACT- A wealth of evidence suggests that plants differentially drive rhizosphere microbial community dynamics. Considering the close linkage between plants and microbes in soil biogeochemical cycling we can rationalize that plants may exert a species-specific 'legacy effect' on the soil microbial community. We hypothesize, that when a plant is removed from an ecosystem and replaced with a new species, its 'legacy effect' on the soil community will differentially vary based on the influence of the new plant species. To test this hypothesis we constructed plant/soil mesocosms using soils from an agroecosystem maintained as a Zea mays monoculture for over 50 years. We selected replacement species that exhibit a diversity of ecophysiological traits and planted them into the mesocosms. A maize mesocosm representing the original plant species was planted as a reference, and the microbial community in its rhizosphere was termed the baseline or maize 'legacy' community. Soil Sampling was conducted at five points, at each time point soil community structure was assessed using PCR-DGGE. Similarities and differences between rhizosphere microbial communities were assessed using computer analysis of fingerprint profiles, then similarity matrices and ordination analysis were used to interpret the data. We describe 'legacy effect' in terms of similarity in microbial community profiles between the replacement species and the maize baseline community. We also measure 'legacy' by classifying dominant microbial species that persist or are absent in the rhizosphere of replacement species. Analysis of soil microbial community profiles revealed that microbial community structure differentially changed in the rhizosphere of the replacement plants. Similarity distances from the maize baseline community, ranked most to least similar was as follows; Triticale: Triticosecale, Soybean: G. max, Alfalfa: M. sativa,, Hairy Vetch: V. villosa. , Ryegrass: L. multiflorum. We conclude that a plant species 'Legacy effect' on the associated microbial community differs based on its replacement plant and this effect may be important in describing plant microbe interactions in agroecosystems and invasive plant ecological studies.
Key words: microbial ecolgy, plant legacy effect, rhizosphere, agroecosystem