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Epiphytic lichen biomass accumulates slowly in forest canopies. We evaluated three alternative hypotheses for the slow accumulation of epiphytic lichens, using two experiments in tree crowns from 15 Douglas‐fir forest stands representing three age classes: old growth, young, and recent clearcuts. The first experiment evaluated whether forest age, bark roughness, or dispersal rate limits the establishment of the dominant old‐growth‐associated lichen, Lobaria oregana. Surface‐sterilized branches with either rough or smooth bark were repeatedly inoculated with propagules and compared 1 yr after the last inoculation. Dispersal affected rates of establishment: inoculated branches had 27× more newly established thalli than controls. Establishment on smooth bark was highest in clearcuts, intermediate in young forests, and lowest in old growth. There was as much or more establishment of sown propagules on smooth‐barked branches as on rough‐barked branches in all age classes. In the second, transplant‐performance experiment, Lobaria oregana grew as rapidly in young forests as in old growth but lost biomass and suffered more injuries in clearcuts. In contrast, L. pulmonaria performed at least as well in clearcuts as in young forests and old growth. Poor dispersal and establishment limit the development of L. oregana populations in Douglas‐fir forests. Particular substrates and microenvironments found only in old growth are not essential for Lobaria establishment and growth. Maximizing the number and dispersion of remnant trees in cutting units should maximize the rate of accumulation of L. oregana biomass in the regenerating forest. The single most important action promoting the accumulation of old‐growth‐associated epiphytes will be the retention of propagule sources in and near all cutting units.

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The “New Forestry” practice of green‐tree retention is becoming an important management tool for publicly owned lands, yet few data exist to demonstrate that this tool can succeed at enhancing biodiversity. We addressed this issue by using a retrospective approach to compare canopy lichen litter in adjacent, paired stands of rotation age (55–120 yr): one with and one without old‐growth (>300 yr) remnant trees. We sampled three functional groups of lichens in 17 stands in western Oregon: alectorioid lichens, cyanolichens, and green‐algal foliose lichens. Thirteen stands were low elevation (520–850 m) and four were mid‐elevation (1220–1340 m). Biomass of cyanolichen and green‐algal foliose lichen litter was greater in low‐elevation sites, whereas alectorioid lichen litter biomass was greater in mid‐elevation sites. Cyanolichens were absent from all mid‐elevation sites. Biomass of alectorioid lichen and cyanolichen litter was greater in low‐elevation sites with remnant trees than in those without remnant trees by 86% and 233%, respectively. The biomass of green‐algal foliose lichen litter was 80% greater in mid‐elevation sites without remnant trees than in those with remnant trees. Total lichen litter biomass was slightly, but not significantly, greater in stands with remnant trees at both low elevations (by 23%; ∼370 kg/ha standing biomass in remnant stands) and mid elevations (by 12%; ∼470 kg/ha standing biomass). Cyanolichen litter biomass was positively related to the number of remnant trees present; alectorioid and green‐algal lichen litter biomass were negatively correlated with the density of trees in the regeneration cohort. Because retaining live remnant trees will differentially affect these three functional groups of macrolichens, managers must be clear as to their objectives before using green‐tree retention as a tool to enhance biodiversity.

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