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Bryophyte flora and vegetation on the island of Graciosa (Azores), with remarks on floristic diversity of the Azorean islands
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Abstract(s)
Para a brióflora da Graciosa estavam referidas 17 espécies. Este valor é agora alargado para 107 spp. Os dados recolhidos fornecem novos conhecimentos sobre a autoecologia de alguns briófitos: novos limites de altitude para algumas espécies; as preferências de substrato mostraram ser mais acentadas as baixas altitudes do que na zona da "floresta húmida"; as espécies de altitude mostram, nesta ilha maiores exigências de ensombramento e de substrata húmido do que as suas populações, em maiores altitudes, noutras ilhas do arquipélago. Distinguem-se as briocomunidades como epífita, Frullanietum microphyllae; associação Tetrastichium - Dumortiera como epílitica – epigeica, a aliança Grimmia azorica - Ptychomitrium como epílitica (incluído o Grimmietum azoricae e o Ptychomitrietum polyphylae de V. HÚBSCHMANN 1974); e a aliança Myuryum - Allorgea - Fissidens pallidicaulis como epigeica (compreendendo as mini-associações Fissidentetum serrulati, Fissidentetum pallidicaulis e Diphyscietum foliosi de V. HÚBSCHMANN 1974). A análise de diversidade florística das ilhas dos Açores mostra não haver uma correlação positiva desta com o tamanho da ilha ou com os factores topográficos. Por outro lado, as ilhas com altitude mais elevada mostram possuir valores de diversidades altos e semelhantes entre si, independentemente da área. Para a ilha da Graciosa, a grande variedade de habitats costeiros ajuda a explicar a alta diversidade relativa da sua flora vascular acima dos valores esperados, se considerarmos a sua área e altitude. Igualmente, a diversidade da sua brióflora é, inesperavelmente, elevada, já que grandes extensões da ilha são pobres em espécies.
ABSTRACT: The bryoflora of Graciosa was earlier documented to be 17 spp. This figure has now been changed to 107 spp. The documentation of the bryoflora of Graciosa has provided new knowledge on the autoecology of several bryophytes; several have got wider altitude ranges; substratum preferences are more pronounced at low altitude levels than in the cloud-zone forest; high altitude species have more pronounced demands for shelter and substratum moisture on Graciosa than at altitudes on other islands in the archipelago. Bryophyte communities distinguished; The epiphytic Frullanietum microphyllae; the epilithic epigeic Tetrastichium - Dumortiera - association; the epilithic Grimmia azorica - Ptychomitrium - alliance (including the Grimmietum azoricae and Ptychomitrietum polyphylae de V. HÚBSCHMANN 1974); the. Myuryum - Allorgea - Fissidens pallidicaulis - all. (comprising the mini-associations Fissidentetum serrulati, Fissidentetum pallidicaulis, Diphyscietum foliosi by V. HÚBSCHMANN 1974). Plant diversity on the Azorean islands is not positively correlated to island size or topographical features. However, high altitude provides high and equally high diversity figures on islands of widely .different size. Richly varied habitat conditions within the coastal zone on Graciosa helps to explain the high vascular plant diversity of the island widely differing from that of other Azorean islands, if their size and altitude are considered. The bryophyte diversity on Graciosa is unexpectedly high, as most parts of the island are species-poor.
ABSTRACT: The bryoflora of Graciosa was earlier documented to be 17 spp. This figure has now been changed to 107 spp. The documentation of the bryoflora of Graciosa has provided new knowledge on the autoecology of several bryophytes; several have got wider altitude ranges; substratum preferences are more pronounced at low altitude levels than in the cloud-zone forest; high altitude species have more pronounced demands for shelter and substratum moisture on Graciosa than at altitudes on other islands in the archipelago. Bryophyte communities distinguished; The epiphytic Frullanietum microphyllae; the epilithic epigeic Tetrastichium - Dumortiera - association; the epilithic Grimmia azorica - Ptychomitrium - alliance (including the Grimmietum azoricae and Ptychomitrietum polyphylae de V. HÚBSCHMANN 1974); the. Myuryum - Allorgea - Fissidens pallidicaulis - all. (comprising the mini-associations Fissidentetum serrulati, Fissidentetum pallidicaulis, Diphyscietum foliosi by V. HÚBSCHMANN 1974). Plant diversity on the Azorean islands is not positively correlated to island size or topographical features. However, high altitude provides high and equally high diversity figures on islands of widely .different size. Richly varied habitat conditions within the coastal zone on Graciosa helps to explain the high vascular plant diversity of the island widely differing from that of other Azorean islands, if their size and altitude are considered. The bryophyte diversity on Graciosa is unexpectedly high, as most parts of the island are species-poor.
Description
Keywords
Briófitas Plantas Epífitas Ilha Graciosa (Açores) Açores Bryophyte Epiphytic Plants Azores
Citation
SJÖGREN, Erik (1990). Bryophyte flora and vegetation on the island of Graciosa (Azores), with remarks on floristic diversity of the Azorean islands. "Arquipélago. Boletim da Universidade dos Açores: Ciências da Natureza", 8: 63-96.