In 1999 we established an NSF-funded Microbial Observatory at the H.J. Andrews Experimental Forest. It was devoted to studying microbial community composition and activity in high-elevation meadows and forests. The current focus of our research at the Microbial Observatory is to examine microbial communities and activities associated with ectomycorrhizal (EcM) fungal mats. Through their activities, EcM mats can create a unique soil environment and likely result in the establishment of distinct microbial communities and activities. Our first research objective was to survey the phylogenetic diversity of EcM mat fungi in old-growth and second-growth stands dominated by Douglas-fir. Phylotyping by PCR-RFLP and sequencing found that species of Piloderma were the dominant mat-forming fungi in all stands, and that species of Ramaria and Hysterangium were of secondary importance in old-growth and second-growth stands, respectively. Our second objective was to survey soil chemical and biological properties of mat and non-mat soils in selected stands containing these dominant EcM phylotypes. We have compared soil chemical properties, such as pH, inorganic N, base cations, and oxalate concentrations of mat and non-mat soils. Biological properties such as the activities of enzymes involved in processing organic C and N (e.g., N-acetyl glucosaminidase, urease and protease), soil respiration, net N mineralization, and nitrification potential have been measured. The poster will center on the presentation of results and discussion of the comparative properties of mat and non-mat soils.