9317976 Hartnett This research continues investigations into how mycorrhizal symbioses mediate exchange of nutrients among plants and thereby influence the structure and dynamics of plant communities. A combination of field studies and greenhouse experiments examines the mechanisms controlling patterns of nutrient transfer between plants via mycorrhizal hyphal bridges and the influence of mycorrhyzae on competition among plants and on plant response to grazing. The influence of grazing pressure on the activity of mycorrhizal fungi is also examined. %%% This research is significant in providing new insights into the role played by associations between mycorrhizal fungi and plants in the competition for resources among plant species and interactions between plants and herbivores. The function and structure of communities may be more strongly influenced by mycorrhizal mutualisms than has been previously thought. Information from this research could have important applications to understanding ecosystem function, mineral nutrition of trees and agricultural plants, and the effect of weeds on cultivated plants. ***
