Lichens on down wood in logged and unlogged forest stands

Abstract

Lichen communities of forests often appear to be negatively affected by timber harvest presumably because of reduction of suitable substrate and increased desiccation. We examined species richness and composition of lichens on wood of logs of the same decay class in unlogged stands (>140 years old) and logged, 20- to 30-year-old stands. There was no significant difference in species richness or mean lichen cover between logged and unlogged stands, but species composition differed, including species that were unique to either logged or unlogged stands. Crustose lichens accounted for 71% of rare species and all of the species occurring more commonly in unlogged stands; macrolichens accounted for 82% of common species and 60% of the species occurring more commonly in logged stands. Diameter at breast height and decay characteristics of down wood were the best predictors of lichen richness. Among lichen-rich, decay class 3 logs, relatively small amounts of retained down wood sustained lichen richness equivalent to unlogged stands. It appears important to ensure that decay classes favourable to lichens are retained after harvest.