Epiphytic bryophyte flora in dry environments from the Western Mediterranean: the special case of Sierra Alhamilla (Almeria, South-eastern Spain).

摘要

In dry Mediterranean environments, the epiphytic habitats are generally poor in bryophytes. However, Sierra Alhamilla, a mountain embedded in one of the driest areas in Europe, is an exception. It shelters an evergreen oak wood, whose richness in epiphyte bryophytes is similar to or higher than that of humid mountain ranges from the Iberian Peninsula and North Africa. The genus Orthotrichum, besides dominating the epiphyte communities on tree trunks and bases, is the most diverse group (45% of the catalogue), and comprises a bulk of species (e.g., Orthotrichum scanicum, Orthotrichum ibericum, Orthotrichum speciosum var. brevisetum) that makes this site especially original. The profiles of the recorded bryoflora (dominance of Orthotrichaceae and Pottiaceae, prevalence of cushions and short turfs and high similarity of tree base and trunk bryophyte communities) indicate an epiphytic bryoflora mainly conditioned by the dry climate. However, the species richness and the biogeographical profile (e.g., dominance of temperate element and occurrence of species that have mesic affinities), together with the altitude influence on structure and composition of bryophyte communities, suggest the existence of microclimatic factors that soften the environmental aridity. This softening effect could be more important at higher altitudes, which are floristically richer than the lower ones.