Microhabitat effects on bryophyte species richness and community distribution on exposed rock outcrops in Portugal

Abstract

Background: Rock outcrops have been shown to provide specific conditions for bryophyte communities, but no studies have focused on the importance of microhabitats on such communities. Aim: To analyse the distribution pattern of bryophyte species from granite and schist outcrops in three microhabitats (rock surfaces, fissures and cavities) in Portugal. Methods: Sample plots were established in fissures, cavities and on rock surfaces of rock outcrops in north and central Portugal. Micro-scale variables, such as exposure and slope were assessed for each microhabitat. Results: The microhabitats most different in species composition were surfaces versus cavities and surfaces versus fissures, both on granite and schist. Short-lived shuttle species tended to be associated with surfaces, and perennial species were more frequent in cavities and fissures. Both on granite and schist, the number of species found in each microhabitat was highest in cavities, followed by fissures and rock surfaces. The most relevant predictors of bryophyte richness were microhabitat type, exposure and rock type. Conclusions: This investigation confirmed that rock microhabitats play an important role in bryophyte diversity by promoting habitat heterogeneity. In addition, our results clearly suggest local explanations for variation in bryophyte species richness and communities.