9421199 McCune The dominant epiphytes in old-growth forests develop very slowly, thus epiphyte communities differ greatly between old-growth forests and young forests (<150 years old). This study evaluates three alternative, but not mutually exclusive, explanations for the slow development of old-growth associated epiphytes: (1) old-growth epiphytes demand the particular microclimate created by the structure of old forests, (2) old-growth epiphytes are dispersal limited; i.e., suitable habitats are underused by epiphytes because of poor dispersal abilities, and (3) colonization is slow because of a shortage of suitable substrates in young forests. These objectives will be met by two experiments: a growth experiment based on transplanted individuals, and a dispersal/establishment experiment based on artificially sowing propagules onto different substrates in contrasting environments. This proposed work will not only make a contribution to the basic science of epiphytes, it also has great potential to influence forest management. Management options greatly expanded in 1993 because of the move away from clearcutting to "green-tree retention" cutting. Forest managers urgently need information from ecologists on the consequences of alternative densities and spatial arrangements of remnant trees. The alternative outcomes will influence not just epiphytes, but all of the other ecosystem components that depend on epiphytes, either for food, mineral nutrition, nesting materials, or habitat.
