The catalogue of the epiphytic bryophyte flora of the Rif Mountains includes a total of 72 taxa, of which 66 are mosses and six are liverworts. Some new records are provided: Hypnum resupinatum and Tortula israelis, new to northern Africa, Antitrichia curtipendula and Cryphaea heteromalla, new to Morocco, and Dicranoweisia cirrata, Isothecium alopecuroides and Orthotrichum macrocephalum, new to
... [Show full abstract] the Rif Mountains. Epiphytic communities in the different forest types have been analysed, with the conclusion that altitude and humidity are the main factors that determine their composition. The epiphytic stratum is best developed at the highest altitudes on the Principal chain and Tazzeka Mountain, where taxa of the genus Orthotrichum dominate or co-dominate the epiphytic communities: O. lyellii and Antitrichia californica co-dominate in the montane zones, while O. speciosum var. brevisetum and Pterigynandrum filiforme co-dominate at the highest altitudes. In lower areas, the abundance of epiphytic bryophytes depends on humidity conditions and the presence of a forest canopy. The best preserved forests, where exposed to oceanic winds, are dominated by hygrophilous taxa, such as Neckera pumila, Cryphaea heteromalla and Frullania dilatata , whereas the dry ones are dominated by thermophilous taxa, such as Orthotrichum tenellum. Finally, ubiquitous species, such as Orthotrichum diaphanum and Bryum capillare, are abundant in disturbed forests.