Richness preservation in a fragmented landscape: a study of epiphytic bryophytes in an Atlantic forest remnant in Northeast Brazil

Fragmentation and loss of habitat are considered to be the main causes for the decrease in biological diversity in tropical forests. This study aims to evaluate the size and edge effects on tree physiognomy and on the bryophyte community structure in relation to richness, composition, and distribution of ecological groups. Ten forest fragments from the Murici Ecological Station, in the state of Alagoas (Brazil) were studied. In each fragment 10 evenly spaced plots were delimited along four 100 m transects located perpendicularly to the border. One hundred and six species were found, of which 56 were liverworts and 50 were mosses. Results showed that flora impoverishment and other variations in the bryophyte community structure are related to fragment size. Shade epiphytes were the most affected. An 'edge effect' was not detected in this study. Vegetation physiognomy parameters contributed partially to the bryophytes' responses. Diameter at breast height, height, and the density of trees were both positively correlated with bryophyte richness, while canopy openness was not. Our results suggest that the larger fragments are better structured physiognomically, i.e. the trees are taller and have larger diameters, which are probably important factors in enabling them to retain a rich bryophyte flora.