Epiphytic bryophytes in Canarian subtropical montane cloud forests: the importance of the time since disturbance and host identity

摘要

The aim of this study was to determine the short- and medium-term effects of forestry practices on epiphytic bryophyte communities growing on whole trees of three host species ( Erica arborea L., Laurus novocanariensis Rivas-Mart., Lousa, Fern. Prieto, E. Dias ,J. C. Costa & C. Aguilar, Myrica faya Aiton) in subtropical montane cloud forests on La Palma ( Canary Islands, Spain). Specifically, we investigated differences in temporal and spatial shifts of species composition and richness of phylogenetic groupings among host species. The most common harvest method in the study area is clear-cutting. Four different postharvest successional stages ( 8, 15, 25, and 60 years after harvest) were studied. Temporal bryophyte species turnover varied according to host species. Most of the later-successional bryophytes with narrower ecological requirements had low abundances on L. novocanariensis; this host experienced a gradual increase of epiphytic richness along the chronosequence. Temporal changes for E. arborea and M. faya were different; they showed increasing richness during the second period (15-25 years) followed by a drop in richness during the last period (25-60 years), and early-successional species dominated throughout the chronosequence. We conclude that the protection of "old-growth stands'' containing trees of selected species can contribute to the survival of epiphytic bryophytes in managed cloud-forest landscapes.