Wood-decay (saproxylic) species are associated with the decomposition of woody tissues and their agents, notably fungi, or are predators of other saproxylic species.
Many species develop in specific microhabitats, some of which are mostly or entirely restricted to mature trees. Many of the rarest species are dependent on the presence of ancient trees, whose age can be measured in centuries. For these species, the rarity and isolation of prime habitat in the modern landscape makes colonisation of new sites all but impossible.
The epiphyte fauna includes grazers of algae, lichens and mosses on the surface of trunks and branches, as well as their predators and parasites.