BRANCH EPIPHYTE ASSEMBLAGES IN THE FOREST INTERIOR AND ON THE CLEAR-CUT EDGE OF A 700-YEAR-OLD DOUGLAS-FIR CANOPY IN WESTERN OREGON

A total of 65 epiphyte species (macrolichens, bryophytes, and a fern) were found on the branches of four 700-year-old Douglas fir trees, two growing in the forest interior and two growing on the edge of a 20-year-old clearcut. The moss Antitrichia curtipendula and the cyanolichen Lobaria oregana dominated the epiphyte assemblages. Branch epiphyte assemblages were similar to those reported for a 450-year-old Douglas fir forest, but A. curtipendula and Pseudocyphellaria rainierensis were much more abundant in the older forest. Epiphyte species tended to be positively associated with other members of their functional group. Alectorioid and ''other'' lichens tended to be negatively associated with bryophytes. Several species were closely associated with moss mats. Ordination revealed one dominant gradient in epiphyte composition that was correlated with height. The gradient could be partitioned into an exposed portion with high lichen cover and low bryophyte cover, an intermediate portion, and a sheltered portion dominated by bryophytes. Biomass and species richness of macrolichen litterfall did not differ between the forest interior and clearcut edge, but there were some differences in the vertical distributions of epiphytes. The exposed and intermediate portions of the compositional gradient extended farther down in the crowns of the edge trees. After two decades of exposure on a clearcut edge, moss mats and associated species were still widely distributed within the edge tree crowns.