Briófitas do Parque Nacional das Nascentes do rio Parnaíba, cerrado brasileiro.

Abstract

The Nascentes do Rio Parnaíba National Park (NRPNP) is the largest conservation unit in the Brazilian Cerrado (729,800 hectares), encompassing the second largest hydrographic basin in the Northeastern region (Parnaíba River) and has a diverse vegetation cover, including fields, savannas, savannas or swamps or buritizais, gallery forests and riparian forests. The vascular flora of the park is poorly known, while the avascular flora (bryophytes) remains unknown. The general objective of this dissertation was to understand the bryophyte flora in different types of environments in the NRPNP, and the landscape aspects that determine the structuring of bryophyte communities in riparian forests. The first objective was to investigate the richness and composition of the bryophytes from the NRPNP in different environments, as well as the preferred substrates, reproductive aspects and the geographic distribution of the species (Chapter I). Four new occurrences were found for the Cerrado and Frullania eboracensis, a new record for Brazil. The gallery forest had the highest species richness (72 spp.), followed by vereda (17 spp.) and cerrado sensu stricto (11 spp.). The most colonized substrate was rocks (56 spp.). Monoecious species predominated over dioecious species. The second objective was to investigate how landscape aspects shape bryophyte communities in riparian forests in the Brazilian Cerrado, to answer the following question: How do landscape characteristics of riparian forests influence the richness, abundance and composition of bryophyte species? (Chapter II). It was found that heterogeneity between environments is an important factor in determining the diversity of bryophytes in riparian forest ecosystems, and that altitude significantly influenced the richness, abundance and composition of bryophytes in these forests, even at altitudinal gradients of approximately 100 meters. Variables related to humidity on a landscape scale had little importance in models of species richness and abundance, while distance from the waterfall influenced negatively the composition of bryophytes in the riparian forests of the NRPNP. The results of this dissertation indicated that the NRPNP environments present a high diversity of bryophytes, especially gallery forests, and that the structure of bryophyte communities in riparian forests in the Cerrado is shaped by environmental heterogeneity and forest topography, with subtle variations at altitude an important predictor of bryophyte distribution.