Dozens of lichens are demonstrated old-growth associates. Some of these are fairly common and develop high biomass (to well over 1 ton dry weight per hectare) in old forests. These include cyanolichens (especially Lobaria oregana) and forage lichens (especially Alectoria sarmentosa, Usnea longissima, and Usnea scabrata).
Other old-growth associates are relatively rare. Of those, Pseudocyphellaria rainierensis and Nephroma occultum stand out as well-documented examples. These never achieve high biomass, instead occurring sparsely in our oldest forests, and very rarely in young forests.