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


Graduation date: 1996This thesis includes four separate studies. The first two studies assessed edge effects in a\ud 700-year-old forest. After 20 years of exposure, epiphyte assemblages on the clearcut edge\ud were similar to those of the forest interior, but there were some differences in vertical\ud distribution patterns. Several species restricted to the upper canopy of the forest interior\ud occurred farther down in the crowns of trees on the clearcut edge. Many species were\ud associated with thick moss mats. Thalli of two cyanolichen species were reciprocally\ud transplanted among four tree crowns. Lobaria oregana grew less on the clearcut edge than\ud in the forest interior. Populations of Pseudocyphellaria rainierensis had acclimated to the\ud edge environment. The third study evaluated whether these two species require old growth\ud and/or thick, underlying moss mats to achieve normal rates of growth and mortality. Thalli\ud were transplanted into tree crowns in 13 forest stands representing 4 age classes: old\ud growth, mature, young, and recent clearcut. Wooden racks were used instead of trees in\ud clearcuts. Half of the cyanolichen thalli were transplanted onto thick moss mats, half onto\ud bare bark. Both species grew at least as well in the younger forests as they did in old\ud growth, but growth rates were significantly lower in clearcuts. Mortality rates were very\ud low in young, mature, and old-growth forests but high in clearcuts. P. rainierensis grew\ud significantly better on moss than bare bark. The fourth study evaluated the long-term\ud potential of live tree retention for cyanolichen conservation. Lichen litterfall was sampled\ud in a natural, multiple-age stand containing remnant trees and regenerating forest. Two\ud lichen species (L. oregana and Sphaerophorus globosus) were strongly associated with\ud remnant trees. Biomass of both species was highest near remnant trees and was\ud significantly higher within groves of remnant trees than at the edges of these groves or near\ud isolated trees. Cyanolichen populations appear to have persisted on remnant trees since\ud before the last fire. They are slowly recolonizing the regenerating forest. Retention of live\ud trees, including hardwoods, combined with longer rotation periods, has great potential to\ud maintain cyanolichens in managed forests

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