Estrutura populacional e desenvolvimento da fase esporofítica de Cyathea delgadii Sternb. (Cyatheaceae, Monilophyta) no sul do Brasil

Abstract

RESUMO -(Estrutura populacional e desenvolvimento da fase esporofítica de Cyathea delgadii Sternb. (Cyatheaceae, Monilophyta) no sul do Brasil). Cyathea delgadii Sternb. é uma samambaia arborescente que ocorre em florestas primárias e secundárias da região nordeste até o sul do Brasil. O presente estudo discute a estrutura populacional e o desenvolvimento da fase esporofítica (crescimento do cáudice, produção de frondes, fenologia da produção de esporos) de C. delgadii, em floresta secundária, no Estado do Rio Grande do Sul, Brasil, baseado na observação de 41 plantas, durante 13 meses. A espécie apresentou padrão espacial agregado e uma freqüência expressivamente alta de indivíduos de menor altura, indicando um grande potencial de regeneração da população. O cáudice das plantas cresceu, em média, 4,65 cm ano -1 , sendo que as maiores taxas de crescimento foram registradas em plantas mais altas. As taxas de produção de frondes novas (5,75 frondes ano -1 ) e de senescência (4,92 frondes ano -1 ) similares evidenciaram uma capacidade de manter um número de frondes estável. Poucas plantas formaram frondes férteis, sendo que a produção e liberação dos esporos ocorreram assincronicamente.Palavras-chave: pteridófita arborescente, ecologia, distribuição espacial, fenologia, taxa de crescimento ABSTRACT -(Population structure and development of the sporophyte phase of Cyathea delgadii Sternb. (Cyatheaceae, Monilophyta) in Southern Brazil). Cyathea delgadii Sternb. is a tree fern that grows in primary and secondary forests from Norhteastern to Southern Brazil. This study discusses the population structure and development of the sporophytic phase (caudex growth, frond production, phenology of spore production) of C. delgadii in a secondary forest in the State of Rio Grande do Sul, Brazil, based on observations of 41 plants during a 13 month period. The species had an aggregated spatial distribution pattern and higher frequency of smaller individuals, indicating high potential for population regeneration. On average, the caudex of plants grew 4.65 cm year -1 , and the highest growth rates were recorded for taller plants. The similar frond production rate (5.75 fronds year -1 ) and senescence rate (4.92 fronds year -1 ) reflect the capacity to maintain a stable number of fronds. Only a few plants formed fertile fronds, while spore production and liberation occur in an asynchronous pattern.

Phenology, caudex growth and age estimation of Cyathea corcovadensis (Raddi) Domin (Cyatheaceae) in a subtropical forest in southern Brazil

“…This more continuous pattern of leaf emergence and senescence, albeit irregular, has also been reported for C. delgadii Sternb. (Schmitt & Windisch 2007) and C. atrovirens (Schmitt & Windisch 2012) in Rio Grande do Sul, probably because of the similar weather patterns.…”

“…The same trend in leaf emergence in taller C. corcovadensis plants was also reported by Schmitt & Windisch (2003; for Alsophila setosa and C. delgadii, as well as by Tanner (1983) for C. pubescens. Taller plants capture more light in the understory, which increases their productivity and leaf development rate (Schmitt & Windisch 2007). In El Salvador, Seiler (1981) found no association between leaf emergence and height in A. salvinii Hook., which grows in fully illuminated areas.…”

“…In El Salvador, Seiler (1981) found no association between leaf emergence and height in A. salvinii Hook., which grows in fully illuminated areas. According to Schmitt & Windisch (2007), the fact that the tallest C. delgadii plants are more exposed to desiccation might be attributable to their higher numbers of senescent leaves. The tendency to greater fertility among taller plants might favor the dispersion of spores through the wind, which was also found for C. lasiosora (Mett.…”

“…(33%) from Japan; by Mehltreter & García-Franco (2008) in Alsophila firma (Baker) D.S. Conant (25%) from Mexico; and by Schmitt & Windisch (2006b) in A. setosa (8.88%), Schmitt & Windisch (2007) in C. delgadii (9.75%) and Schmitt et al (2009) in Dicksonia sellowiana (38%) from southern Brazil.…”

Estructura poblacional y características del hábitat de dos especies de Cyatheaceae del estado de Hidalgo

“…nes o de tamaño pequeño), en varias especies de helechos arborescentes, por ejemplo en Alsophila auneae (Tanner, 1983), Cyathea spinulosa (Nagano y Suzuki, 2007) y Dicksonia sellowiana (Schmitt et al, 2009), es un indicador de que tienen un alto potencial de regeneración y expansión (Schmitt y Windisch, 2007;Schmitt et al, 2009), y de que se desarrollan bajo condiciones micro-ambientales favorables para el establecimiento, tanto de los gametofi tos como de los esporofi tos (Bernabe et al, 1999;Mehltreter y García-Franco, 2008). Sin embargo, este tipo de poblaciones con predominio de individuos jóvenes, también puede ser producto de la acción de otros factores externos: v. gr.…”