Distribution of epiphytic macrolichens in relation to remnant trees in a multiple-age Douglas-fir forest

Abstract

Alternatives to clear-cutting are being implemented to increase biodiversity of managed forests in the Pacific Northwest. Lichens are an integral component of old growth, but lichen biomass develops slowly in forests. We evaluated the long-term potential of live tree retention for lichen conservation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. We sampled lichen litterfall in a 2-ha stand that contained 200- to 600-year-old remnant trees scattered in a forest composed mostly of 100-year-old trees that established following fire. We used association, principal components, and regression analyses to relate lichen litterfall biomass to the proximity of remnant trees. Two epiphytic lichens were strongly associated with remnant trees: the foliose cyanolichen Lobaria oregana (Tuck.) Müll. Arg. and the fruticose green algal lichen Sphaerophorus globosus (Hudson) Vainio. Biomass of both species was highest near remnant trees, and biomass was slightly higher within groves of remnant trees than it was at the edges of these groves or near isolated trees. Lichens appear to have persisted on remnant trees through the last fire and are slowly recolonizing younger trees from this source of propagules. Retention of live trees, maintenance of hardwoods, and longer rotation periods have great potential to maintain old-growth-associated lichens in at least some managed forests.