An Ecologic Study of Epiphytic Bryophytes and Lichens on Pseudotsuga menziesii on the Olympic Peninsula, Washington. I. A Description of the Vegetation

Six epiphytic vegetational unions occur on northeast and southwest exposures of Pseudotsuga menziesii in mature forests of the Olympic Peninsula, Washington. The Hypnum circinale-Dicranum fuscescens-Scapania bolanderi Union and the Hypnum circinale-Dicranum fuscescens-Lepraria membranacea Union both occur in very mesic habitats. The Hypnum circinale-Lepraria mem- branacea Union and the Hypnum circinale-Lepraria membranacea-Sphaerophorus globosus Union occur in habitats of intermediate moisture. The lichen-dominated unions of Platismatia glauca-Parmeliopsis hyperopta-Lepraria membranacea and Alectoria sarmentosa-Parmeliopsis hyperopta-Ochrolechia tartarea-Myco- blastus sanguinarius both occur in relatively xeric habitats. The relationships between epiphytic vegetation and surrounding vascular vegetation are general; bryophyte-dominated unions occur in mesic habitats where the undergrowth is characteristic of the Polystichum munitum Union,