At least two ectomycorrhizal fungi, Hysterangium setchellii and Gautieria monticola, form extensive hyphal mats in the soils of coniferous forests of the Pacific Northwest. Other Hysterangium species form similar mats in coniferous and deciduous forests throughout the world, including H. gardneri in association with Eucalyptus. Preliminary research has demonstrated that the rhizosphere communities dominated by the first two fungi have significantly elevated microbial biomass, respiration rates and altered levels of seven enzymes responsible for organic matter decomposition when compared to adjacent uncolonized soils. Since these mats offer discrete units to study the influence of ectomycorrhizae on the microbial ecology of the rhizosphere community, we propose to compare the above three mat communities with uncolonized soils in terms of: fungal and bacterial biomass, community respiration and enzyme activities; the partitioning of nitrogen and phosporus into labile and recalcitrant pools; the effects of mat chemistry on enzyme activities; enzyme production by pure fungal cultures; and the role of phenolic-coupling enzymes in rhizosphere processes.
