Bryophytes are familiar and attractive components of many natural landscapes such as peatlands, tundra environments and moist forests, where their shaggy coverings on branches, crags and boulders, add distinction to the landscape (Figs. 2.1,2.2). In particular, epiphytic bryophytes make up a conspicuous portion of many rain forest canopies, hanging from branches (Fig. 8.6) and densely festooning tree trunks (Wolf 1993, Kürschner & Parolly 2004).

Less appealingly, they also occasionally grow on unexpected substrates, like the leather of a discarded boot, or a rusty iron pipe. Even in modern cities where air pollution and the man-made environment may seem unrelenting, bryophytes are able to colonize crevices in masonry (Bates 2000). The occurrence of bryophytes in a wide range of terrestrial and freshwater habitats suggests intriguing questions on how they manage to colonize, adapt and develop in such environments. The occurrence of bryophytes in nearly every ecosystem on earth (all but salt water and permanently frozen ecosystems) also raises questions about their ecological significance in those ecosystems. This is the focus of the present chapter, where we will explore the contribution of bryophytes to ecosystem functioning and, more precisely, how they may influence vegetation dynamics, soil formation and characteristics, global geochemical cycles and hence, climate regulation.

Water and biogeochemical cycles

Bryophytes contribute to a substantial proportion of the global biomass in a range of ecosystems (Fig. 2.3) and hence play a major role in the cycling of carbon and nutrients through growth and decomposition.