Canopy epiphyte studies in the central Oregon Cascades: implications for the management of Douglas-fir forests

This thesis includes four separate studies. The first two studies assessed edge effects in a.700-year-old forest. After 20 years of exposure, epiphyte assemblages on the clearcut edgewere similar to those of the forest interior, but there were some differences in verticaldistribution patterns. Several species restricted to the upper canopy of the forest interioroccurred farther down in the crowns of trees on the clearcut edge. Many species wereassociated with thick moss mats. Thalli of two cyanolichen species were reciprocallytransplanted among four tree crowns. Lobaria oregana grew less on the clearcut edge thanin the forest interior. Populations of Pseudocyphellaria rainierensis had acclimated to theedge environment. The third study evaluated whether these two species require old growthand/or thick, underlying moss mats to achieve normal rates of growth and mortality. Thalliwere transplanted into tree crowns in 13 forest stands representing 4 age classes: oldgrowth, mature, young, and recent clearcut. Wooden racks were used instead of trees inclearcuts. Half of the cyanolichen thalli were transplanted onto thick moss mats, half ontobare bark. Both species grew at least as well in the younger forests as they did in oldgrowth, but growth rates were significantly lower in clearcuts. Mortality rates were verylow in young, mature, and old-growth forests but high in clearcuts. P. rainierensis grewsignificantly better on moss than bare bark. The fourth study evaluated the long-termpotential of live tree retention for cyanolichen conservation. Lichen litterfall was sampledin a natural, multiple-age stand containing remnant trees and regenerating forest. Twolichen species (L. oregana and Sphaerophorus globosus) were strongly associated withremnant trees. Biomass of both species was highest near remnant trees and wassignificantly higher within groves of remnant trees than at the edges of these groves or nearisolated trees. Cyanolichen populations appear to have persisted on remnant trees sincebefore the last fire. They are slowly recolonizing the regenerating forest. Retention of livetrees, including hardwoods, combined with longer rotation periods, has great potential tomaintain cyanolichens in managed forests.