Observations were made in 15 permanent 0.25-ha forest study areas in and near the H.J. Andrews Experimental Forest (Hawk et al. 1978, Franklin and Van Pelt 1990) near Blue River, Oregon, in the western Cascades. These sites were chosen to span the range of the environmental gradient discussed by Zobel et al. (1976), extending from warm and dry to cold and wet sites. Four of the 15 sites were mature forest, 130 to 150 years old, and the other 11 sites were old-growth forest, more than 400 years old.
Nomenclature follows Anderson, L.E., H.A. Crum, and W.R. Buck. 1990. List of the mosses of North America north of Mexico. The Bryologist 93: 448-499. Sampling took place from June to August, 1991. Cover was estimated visually to the nearest 1% (within a 20- by 50-cm Daubenmire (1959) frame) for each species on 30 microplots on the forest floor, 30 on logs, and 15 on tree bases at each of the 15 sites. The Daubenmire frame was systematically placed on the forest floor (with logs and rocks avoided) every 5 m along three parallel transects within a 50-m2 plot. Frames were also placed on downed logs that had just begun to lose some of their bark; logs were chosen so that decay was as uniform as possible. Because bryophyte communities on the tops and sides of logs differ, only the upper surface was sampled. Finally, frames were placed to lean against the bases of overstory trees (with the 20-cm side down); the north side of trees was arbitrarily chosen for consistency. Cover was then averaged by species and substrate for all microplogs within a site. Pearson correlation coefficients were used to assess the relationship between elevation and total cover of each species in each stand. Constancy was computed as the percentage of sites in which a species occurred out of the 15 sites examined.
Frequency on each substrate at each site was computed as the percentage of microplots containing the species divided by the total number of microplots for the substrate and site. Species substrate affinities were assigned only when average cover across all sites was greater than 1%. Substrate affinities are shown for species that occur on one substrate at least twice as often as on the next most common substrate. These substrate rankings were based on the species' frequency on that substrate across all sites.
Vouchers were deposited in the Oregon State University Herbarium, Corvallis, Oregon.
