Abstract
This study aimed to compare the richness and composition of the epiphytic bryoflora between várzea and igapó forests in Caxiuanã National Forest, Brazilian Amazon. Bryophytes were collected on 502 phorophytes of Virola surinamensis. Average richness per phorophyte and composition between forests and between dry and rainy periods was tested by two-way analysis and by cluster analysis, respectively. In total, 54 species of 13 families were identified. Richness was greater in igapó forest (44 species) compared to várzea forest (38 species). There was no significant difference in the number of species between the studied periods. Cluster analysis showed the bryoflora composition was different between várzea and igapó, but not between dry and rainy periods. Results did not corroborate the hypothesis that várzea forests harbor higher species richness than igapó forests.
Highlights
Tropical rainforests are rich in epiphyte bryophytes due to high humidity levels (Richards 1954, 1984, Uniyal 1999, Germano and Pôrto 1998, Valente and Pôrto 2006, Santos and Costa 2008)
The Caxiuanã National Forest is predominantly composed by dense ombrophilous lowland forests or upland forests (85%), alluvial dense ombrophilous lowland forests or igapó and várzea forests (10%), enclaves of grassland, scrub vegetation, and patches of secondary vegetation resulting from human actions (Almeida et al 2003)
The ordering analysis showed the formation of two groups, and the first arrangement axis completely separates the species composition of epiphytic bryophyte community between the two types of forests, but there was no variation in species composition between dry and rainy periods (Fig. 1)
Summary
Tropical rainforests are rich in epiphyte bryophytes due to high humidity levels (Richards 1954, 1984, Uniyal 1999, Germano and Pôrto 1998, Valente and Pôrto 2006, Santos and Costa 2008). In Amazonia, the richness of plant species, including epiphytes, is strongly correlated with absolute annual rainfall (Gentry 1988). The precipitation is one of the factors defining the floods in forests by white, black or light water rivers, called. Várzea forests are located on river margins and have Andean and pre-Andean origin, being associated with white water rivers, rich in nutrients with high concentration of sediments and dissolved minerals, as well as pH close to neutral. Igapó forests are found on river banks, but have their origin from erosive resistant shields of Guiana and Central Brazil, being associated with black or light water rivers, poor in nutrients, with high amount of dilute organic matter, especially humic and fulvic acids, and an acid pH (Junk and Furch 1980).
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