Vertical distribution of dominant epiphytes in Douglas-fir forests of the central Oregon Cascades
Sillett, Stephen C.
Rambo, Thomas R.
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The canopies of old-growth Douglas-fir forests support a diversity of epiphytic lichens and bryophytes. We quantified the vertical distributions of six dominant epiphytes throughout the crowns of large Tsuga heterophylla (46-57 m tall) and Pseudotsuga menziesii (60-78 m tall) trees in five forest stands of the central Oregon Cascades. There were no major differences in epiphyte distribution between the two tree species, but epiphytes on T. heterophylla generally peaked in abundance at heights 10-20 m below those on P. menziesii. Alectorioid lichens were most abundant in the upper crowns but scarce in the lower crowns. The fruticose green algal lichen Sphaerophorus globosus was evenly distributed throughout the crowns. The cyanolichen Lobaria oregana and the moss Antitrichia curtipendula were most abundant in middle crowns. Lobaria pulmonaria was most abundant in the lower-middle crowns. It was scarce or absent in the upper crowns. The moss Isothecium myosuroides was also scarce or absent in the upper crowns. It was most abundant in the lower crowns. The vertical patterns described in this study are not representative of all old-growth Douglas-fir forests. In wetter forests, bryophytes are dominant throughout the canopy. In drier forests, alectorioid and other green algal lichens extend farther down in the canopy, and bryophytes and cyanolichens are restricted to the lower canopy