PARENT SESSION
Oral Session #57: Plant Competition I.
Presiding: T. Seastedt
Wednesday, August 7. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.
Feeding the microbes: can it confer a competitive advantage in plant-plant interactions?
Suding, Katharine*,1, Bowman, William1, Larson, Julia1, Thorsos, Eileen2, 1 University of Colorado at Boulder, Boulder, CO2 Swarthmore College, Swarthmore, PA
ABSTRACT- While it is widely accepted that litter quality can exert strong effects on microbial growth and composition, the potential for these effects to influence competitive dynamics among plant species has received less attention. Plant species that produce high levels of simple secondary carbon compounds may stimulate microbial growth and increase microbial immobilization of N. We hypothesize that an indirect effect of the production of these compounds may be to decrease of plant available N, an effect analogous to strong competitive effects by the plant itself. We tested this hypothesis in the alpine tundra of the Colorado Front Range with Acomastylis rossii, a rosaceous forb, that produces litter containing as much as 20% dry weight phenolics. Field and greenhouse experiments indicate that Acomastylis litter increases microbial respiration and microbial biomass in a manner similar to carbon (sugar) additions and to a much greater extent than did other litter types. Field removal experiments indicate that the presence of Acomastylis decreases rates of net nitrogen mineralization. Results from a phytometer competition experiment suggest that the competitive ability of a dominant grass, Deschampsia ceaspitosa, declines in areas where the soil/microbial effects of Acomastylis are strongest. Taken together, these results indicate that microbial-mediated positive feedbacks can exist among litter chemistry, resource availability, and competitive ability.
KEY WORDS: plant-soil feedbacks, indirect effects on competitive interactions, phenolic compounds, mircobial N immobilization