The bark of trees provides an important substrate for many lichen species. Though some bark-dwelling (epiphytic) lichens occur incidentally on other substrates as well, most are entirely restricted to this habitat, and could not exist separate from the trees they colonize. The ability of epiphytic lichens to colonize tree bark is dependent on various physical and chemical properties of the bark, including texture, water relations and pH (Barkman 1958). The degree of environmental stability offered by the surrounding forest also affects lichen composition. Though some epiphytic lichens are clearly able to establish under relatively unstable conditions (for example a vigorously growing seral forest where factors such as light, temperature and substrate are in a state of relative flux), others may require a much more stable environment for colonization. There are strong indications that many epiphytic lichen species occur primarily, or even exclusively, in oldgrowth forests. In the British Isles, for example, Rose (1976) demonstrated a strong positive correlation between lichen diversity and forest age. Though little comparable work has been conducted in North America, Lesica et al. (1991) concluded that many lichen species in Montana "will become less common as silvicultural practices continue to convert oldgrowth to younger aged forests". Recent field work in British Columbia (Goward 1991) suggests that current forest practice (especially short rotation forestry with large or progressive clearcuts) may eventually exclude many lichen species from large areas of the province, and may, in some cases, ultimately bring about their complete extirpation. 2 The present pilot study attempts both to quantify the relation between epiphytic lichen diversity and forest age, and to compare the impacts of three silvicultural systems on long-term epiphytic diversity. Specifically, the objectives are: l) to compare epiphytic macrolichen diversity in forests of three age classes: young (30-60 years); mature (120-150 years); and oldgrowth (300+ years). 2) to monitor epiphytic macrolichen diversity over time among two silvicultural systems and unlogged controls. 3) to make tentative recommendations on the most effective silvicultural systems for maintaining epiphytic macrolichen diversity. This study is a component of a larger, multi-disciplinary research project examining the impact of different silvicultural systems, beginning with harvesting systems, on forest structure and function (see Coates et al. 1993).
Goward. 1993. Date Creek Study: Epiphytic Lichen Diversity Progress Report. FLNRORD
Keywords: Silvicultural Systems Research, Interior Cedar-Hemlock Zone, Prince Rupert Forest Region - Date Creek Study: Epiphytic Lichen Diversity Progress Report
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