Ectomycorrhizal Mat Communities: Evaluating the Direct Cycling Hypothesis

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Specialized ectomycorrhizal (EcM) fungi produce extensive perennial hyphal and rhizomorph mats in the litter and soil of coniferous and deciduous forest ecosystems around the world. Our previous work has shown these complex microbial communities to be sites of significantly elevated microbial activity, including nutrient decomposition and cycling. One of the most persistent problems in microbial ecology has been the gap between physiological traits observed in pure cultures and observed or hypothesized activities in nature. Using ectomycorrhizal mat communities as discrete experimental systems, this research will attempt to define the specific role of these ecologically important fungi in the EcM fungus-host tree symbiosis through their capacity to exploit environmentally significant nitrogen and phosphorus resources in decaying soil organic matter. The specific objectives of this research are to: 1) assess the ability of mat-forming EcM fungi to process soil organic matter by changes in substrate nitrogen and phosphorous chemistry and the production of extracellular enzymes, 2) determine how EcM fungi dissociate reactive polyphenol-protein complexes using extracellular enzymes, siderophores or biosurfactants as possible mechanisms, and 3) measure the ectomycorrhizal contribution to soil enzyme activities using polyclonal antibodies raised against enzymes from pure cultures. This research will lead to the understanding of important soil processes associated with soil microbial systems. In particular, this study will elucidate the ability of soil biota to release nutrients from decaying organic matter, and the proficiency of fungi to capture these resources and promote efficient nutrient cycling in ecosystems.