Epiphytic Lichen Abundance: Effects of Stand Age and Composition in Coastal British Columbia

Abstract

Forest management, particularly in zones with infrequent disturbances, changes stand age and structure in ways that impact epiphytic lichen growth and establishment. This study investigates the effects of stand age and type on epiphytic lichen abundance and composition (the relative percentages of alectorioid lichens and cyanolichens) in the Coastal Western Hemlock zone of western Vancouver Island, British Columbia, Canada. We sampled lichens from the litter layer in six young (<70-yr-old), 18 mature (70–200 yr-old) and 40 old-growth (≥300-yr-old) stands of three species compositions (Picea sitchensis and Tsuga heterophylla, Thuja plicata and T. heterophylla, Abies amabilis and T. heterophylla) in four watersheds and in the coastal lowlands of Clayoquot and Barkley Sounds. We examined a subset of 32 stands paired for location and type to further examine the effects of stand age. The paucity of mature stands severely constrained study design. Epiphytic lichen abundance and the percentage of alectorioid lichens increased with stand age, at least up to 120 yr, although not all trends reached statistical significance. Abundance and composition also varied with stand type and location. Relatively high-elevation (>400 m) mature and old-growth T. heterophylla/A. amabilis forests had a high abundance of lichen dominated by cyanolichens; low-elevation forests (<200 m) had a high abundance dominated by alectorioids; mid-elevation forests (300–400 m) had less lichen. Mature stands were either very small or were initiated by natural disturbances, and most contained structural remnants. Because 70–120 yr-old stands with structural remnants had less lichen than paired old-growth stands, we concluded that structural retention, while important, may be insufficient to conserve epiphytic lichens in parts of the Coastal Western Hemlock zone.