The relationship between lichen species richness and forest age was explored in southwestern Nova Scotia by examining the epiphytic lichens in 51 conifer-dominated forest stands with no evidence of harvesting. The stand ages were determined by tree cores and ranged from 52 to 292 years. One hundred and thirty-five lichen species in 61 genera were identified, of which 25 species are new records for Nova Scotia, and two appear to be species new to science. Using the Nova Scotia Department of Natural Resources' age thresholds, 12 of the 135 lichen species were found exclusively in “early old-growth” and 16 were found only in “advanced old-growth” forest stands. These forests have a diverse lichen flora including green-alga containing macrolichens, a spectrum of crustose taxa and eight genera and 21 species of cyanolichens, the latter being found mainly on deciduous trees.

Data on the identified lichen species were used, with the help of two existing indices of ecological continuity, to calculate a value for each of the 51 forest stands assessed. The values should represent an age category (i.e., the higher the value the older the forest stand). The values calculated, however, using either of these indices, were not high enough to identify any of the stands as “old-growth.” In contrast, the stand ages determined using tree cores, showed that some stands were old enough to be defined as “old-growth.” The failure of index 1 to identify any stands as old-growth was likely due to regional ecological variations, suggesting that a new suite of lichens needs to be developed for southwestern Nova Scotia. The problems with index 2, which used calicioid lichens as a predictor of old-growth, appeared to be that insufficient data were collected on these easily overlooked taxa.