Several studies have found that the abundance and diversity of cryptogams (including those on the ground or logs, on boles, and epiphytics) generally increases with stand age (e.g., Lesica et al., 1991; Esseen et al., 1996; McCune, 1993; Stout, 2001).

In the Cedar Creek watershed in the Pacific Northwest, species richness of cryptogams increased from early-seral (6 species), to mid-seral (17 species), to late successional/old-growth (29 species) (Stout, 2001). Lesica et al. (1991) found that leafy lichens were mainly restricted to old growth forests and absent from second growth and nitrogen-fixing foliose lichens were more common in old growth than second growth.

Epiphytic lichens are abundant in old forests, having a biomass sometimes exceeding 1000 kg ha-1 – which is much higher than that in even-aged young forests (Berryman and McCune, 2006). In the coastal western hemlock forests of Clayoquot and Barkley Sounds, epiphytic lichen abundance generally increased with stand age, at least up to 120 years (Price and Hochachka, 2001). Young forests (<70 years old) contained no lichen litterfall while young-mature (70–120 years old) cedar and spruce stands contained less lichen than did paired old-growth stands (>300 years old).

In a chronosequence study in the CWHvm subzone on western Vancouver Island, epiphytic lichens dispersed into regenerating stands, but lichen colonies there were insignificant in comparison to those in older forests in terms of abundance and diversity (Enns et al., 1999). There was an average of about 6 epiphytic lichen species per branch in old growth, compared to 3 species in mature, 2 species in immature and 1 species in regenerating stands. A total of 18 species were found in old growth compared to 14 in mature stands, 13 in immature and 8 in regenerating stands. Some arboreal lichen species were restricted to mature and old growth forests and Cladonia spp. were most abundant in the older stands. A few species were restricted to second growth or immature stands and some species occurred in stands of all ages. Regenerating and immature stands were characterized by species which disperse and colonize rapidly and tolerate extreme conditions, including the fruticose pendulous lichens such as Usnea and Alectoria. Mature and old growth forests had more of the easily fragmented foliose lichens such as Platismatia glauca and species of Hypogymnia.