Effect of deforestation in palm-epiphytic bryophyte communities in a cloud forest in the northern Andes

Abstract

Cloud forests are one of the most diverse and yet one of the most endangered ecosystems in the tropics. Epiphytic bryophytes are extremely diverse and abundant in this ecosystem where the palms are a dominant element. Slash and burn agriculture techniques usually do not cut the palms and they remain as isolated individuals in the middle of artificial grasslands or agricultural fields. Forest clearing creates new environments on the isolated trees that have been considered a refugee for “rare” canopy species, and the relationship of these “isolated” communities with forest communities has been considered to be distant. We sampled 99 plots on 11 individuals of the palm Dictyocaryum lamarckianum for a total effective sampling area of 15.9 m2. The epiphytic communities comprised 72 liverworts and 21 mosses. Diplasiolejeunea alata and D. cavifolia are hereby reported for the first time from Colombia. We analyzed the changes in bryophyte diversity patterns between forests and man-made grasslands and how these patterns are related to the distribution of locally rare species. Our results showed a decrease in the number of species from the bottom to the top of the palm and from the forest to the grassland. Rare species were mostly concentrated in the forest independently of height. Common species moved on average 4 m downward on the palms in the grassland relative to the height on the forest. Ordination of the plots using NMDS provided evidence that the change in species composition is gradual between forests and grasslands and from the base of the palms to the canopy. We propose that the new communities generated by slash and burning practices are a combination of drought tolerant species from the forest and species that are commonly found in disturbed sites. In conclusion, isolated palms are not islands where canopy species can be preserved as they harbor only common species.