Vascular epiphytes of the Atlantic Forest in the Sinos River basin, state of Rio Grande do Sul, Brazil: richness, floristic composition and community structure

Abstract

The Atlantic Forest, which has a vast epiphytic richness, is a priority area for preservation, listed as one of the five most important world hotspots. Vascular epiphyte richness, composition and community structure were studied in two fragments, one of the ombrophilous (29°43'42"S and 50°22'00"W) and the other of the seasonal (29°40'54"S and 51°06'56"W) forest, both belonging to the Atlantic Forest biome in the Sinos River basin, Rio Grande do Sul, Brazil. In each fragment, 40 trees, divided into four ecological zones, were analyzed. In each zone, the occurrence of the species was recorded, and the importance value of each species was calculated according to the frequency of phorophytes and intervals, and cover scores. The Shannon index was calculated for the two communities. In the fragment of the ombrophilous forest (F1), 30 epiphytic species were recorded, and in the seasonal forest (F2), 25. The highest importance value was found for Microgramma squamulosa (Kaulf.) de la Sota in both fragments. The diversity indexes for F1 (H'=2.72) and F2 (H'=2.55) were similar and reflected the subtropical location of the areas. The decrease in mean richness in both fragments in zone 3 (internal crown) to zone 4 (external crown) may be associated with time and space availability for epiphyte occupation and microclimate variations. Exclusive species were found in the areas, which suggest that a greater number of preserved fragments may result in a greater number of preserved epiphytic species in the Sinos River basin.Keywords: vertical distribution, epiphytism, phytosociology, floristic diagnostic, southern Brazil. Epífitos vasculares em Floresta Atlântica da bacia do Rio dos Sinos, estado doRio Grande do Sul, Brasil: riqueza, composição florística e estrutura comunitária ResumoA Floresta Atlântica apresenta uma grande riqueza de epífitos e é considerada uma área prioritária para preservação listada entre os cinco mais importantes hotspots mundiais. A riqueza, a composição e a estrutura comunitária de epífitos vasculares foram estudadas em um fragmento de floresta ombrófila (29°43'42"S e 50°22'00"O) e outro de floresta estacional (29°40'54"S e 51°06'56"O), ambos pertencentes ao Bioma Floresta Atlântica, na bacia do Rio dos Sinos, Rio Grande do Sul, Brasil. Em cada fragmento foram analisadas 40 árvores divididas em quatro zonas ecológicas. Em cada zona, foi registrada a ocorrência das espécies e o valor de importância de cada uma delas foi calculado a partir da frequência nos forófitos e nos intervalos e das notas de cobertura. O índice de Shannon foi aplicado para as duas comunidades. No fragmento de floresta ombrófila (F1) foram registradas 30 e no de floresta estacional (F2) 25 espécies epifíticas. O maior valor de importância foi observado para Microgramma squamulosa (Kaulf.) de la Sota, em ambos os fragmentos. Os índices de diversidade para o F1 (H'=2,72) e o F2 (H'=2,55) foram próximos e refletem a posição geográfica mais subtropical das áreas. A diminuição na riqueza média em ambos os fragmentos da zona 3 (co...

Vascular Epiphytic Diversity in a Neotropical Transition Zone Is Driven by Environmental and Structural Heterogeneity

“…Sampling four vegetation types resulted in double the number of species compared with de la Rosa- Manzano et al (2017), who only sampled two vegetation types. Overall, the low species richness encountered herein is comparable to that of some subtropical forests (e.g., Atlantic and broadleaf temperate forests; Barbosa, Becker, Cunha, Droste, & Schmitt, 2015;Ceballos, Chacoff, & Malizia, 2016;D ıaz et al, 2010;Hsu et al, 2012;Xu & Liu, 2005) but lower than that of other subtropical forests in the southern hemisphere (e.g., Brown, 1990;Hofstede, Dickinson, & Mark, 2001). This low richness may possibly be due to the decreasing number of species per unit area toward the poles, as observed in coniferous forests (e.g., Khine, 2018).…”

Catalogue of the vascular epiphytic flora of Uruguay

“…The predominance of this category has been often reported for epiphytic communities in moist subtropical climates (Gonçalves & Waechter 2003;Barbosa et al 2015;Machado et al 2016). Facultative holoepiphytes (HLF) represent a diverse taxonomic group, commonly varying according to the environmental characteristics, such as the abundance of rocky outcrops (walls or boulders) inside or adjacent to forests.…”

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“…For instance, Becker et al (2014) recorded 30 species near the source of the Rio dos Sinos in Caraá, out of which only three were shared with the present study. Barbosa et al (2015), in a study carried out in an urban park in the lower stretch of the basin, recorded only nine species of epiphytic ferns, four of which were shared with this study. This fact may be associated to vegetation and environment characteristics, since epiphytes, especially ferns, need a healthy environment to develop (Johansson, 1974) and Rocha-Uriartt et al (2015) showed that there is a decreasing gradient in vegetation degradation from the source towards the mouth of the river in the RSHB.…”