Abstract
In tropical forests, tree ferns constitute an important phorophyte for the establishment and occurrence of epiphytic species. Composition, structure and vertical distribution of epiphytic ferns were studied on Alsophila setosa Kaulf., in a semideciduous seasonal forest fragment, in the city of Morro Reuter (29º32'07"S and 51º05'26"W), in the state of Rio Grande do Sul, Brazil. The sample consisted of 60 caudices of at least 4 m high, which were divided in 1 m intervals from the ground. The specific importance value was estimated trough the coverage value and caudex frequency at the intervals. A total of 14 species was recorded, belonging to 10 genera and five families. The highest specific richness occurred in Polypodiaceae. The rarefaction curve for the total sample did not reach an asymptote with an estimated 14.98 to 16.95 species, showing that a few species could still be recorded. The species with the highest importance value and vertical amplitude was Blechnum binervatum (Poir.) C.V. Morton & Lellinger, with a decreasing frequency from bottom to top of the caudex. Considering the predominance of habitual holoepiphytes, the removal of Alsophila setosa caudices compromises microhabitat availability for epiphytes in the forest understory.
Highlights
In tropical forests, epiphytes are an important component of biodiversity, still little known (Mucunguzi 2007)
The present study was developed in a fragment of seasonal semideciduous submontane forest (29o32’07”S, 51o05’26”W, alt. 658 m), in the city of Morro Reuter, in the northeastern region of the state of Rio Grande do Sul, Brazil
Richness estimators indicated a number of epiphytic fern species close to the observed number, so that few species could be added to the total sample
Summary
In tropical forests, epiphytes are an important component of biodiversity, still little known (Mucunguzi 2007). Ferns and lycophytes compose a group of plants worthy of attention within the epiphytic environment, because ca. 2,600 of the 13,600 species in this group (Moran 2008) are epiphytes (Kress 1986). As in other vascular plants, several adaptative strategies that help water and nutrient absorption, and avoidance dehydration, can be observed in epiphytic ferns. Some of the strategies are exceptional, such as those for humus collection, which recreate appropriate conditions for epiphytic plants to capture water and nutrients without maintaining connection to the soil (Dubuisson et al 2008). Other adaptations favor the occurrence of these plants in an epiphytic environment. Among them are poikilohydry; frond trichomes that can complete absorption like roots; small fronds, reduced root system and a long and ramified rhizome; low light saturation point; high tolerance for instability of soil nutrients; as well as wind dispersal of spores (Müller et al 1981; Benzing 1987, 1990; Page 2002; Dubuisson et al 2003, 2008)
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