Bryophyte flora in upland forests at different successional stages and in the various strata of host trees in northeastern Pará, Brazil

摘要

In the northeastern region of the Brazilian state of Pará, approximately 90% of the forested areas are secondary forests. Secondary forests are interesting areas for floristic studies aimed at determining the effects that clear-cutting has on bryophyte communities. The aim of this study was to compare upland forests at different successional stages and the various strata of host trees, in terms of the bryophyte species composition. Bryophyte specimens were collected between August 2005 and September 2006 from host trees in primary and secondary forests of different ages and of different heights, within the municipality of Capit?o Po?o, in the state of Pará. The vertical distribution of bryophytes was evaluated in 15 host trees within the primary forest. We identified a total of 99 bryophyte species: 33 mosses and 66 liverworts. The dominant family was Lejeuneaceae, with 56 species. Most of the species (n = 60) had a neotropical distribution, and 3 species were endemic to Brazil. Cololejeunea minutissima var. myriocarpa (Nees & Mont.) R.M.Schust., Pycnolejeunea papillosa X.-L. He, Radula mammosa Spruce and Verdoornianthus marsupiifolius (Spruce) Gradst. represent new records for the state of Pará. In the successional forests evaluated, we identified 78 species, most of which (n = 38) occurred in primary forest. On the host tree trunks evaluated in the primary forest, we observed 31 species occurring at heights ranging from 2 m to 20 m. Despite the fact that secondary forests account for such a large proportion of the forested areas in Capit?o Po?o, we found that the bryoflora was relatively rich, comprising 31% of the species recorded for the state. The fact that 40% of the species recorded occurred exclusively in the secondary forests and the fact that 45.5% of the species recorded in primary forest occurred within the 2-20 m height range show the importance of studies focusing on bryophytes in secondary forests and in the upper strata of host trees in primary forests.