Crescimento do cáudice e fenologia de Dicksonia sellowiana Hook. (Dicksoniaceae) no sul do Brasil

Abstract

RESUMO -(Crescimento do cáudice e fenologia de Dicksonia sellowiana Hook. (Dicksoniaceae) no sul do Brasil). No sul e sudeste do Brasil, a samambaia arborescente Dicksonia sellowiana Hook. é ainda extraída ilegalmente de remanescentes florestais para uso da capa fibrosa do seu cáudice, bem como para cultivo como planta ornamental. No presente trabalho, o crescimento do cáudice, a produção, expansão e senescência de frondes, bem como a formação e liberação de esporos de D. sellowiana foram estudados com base na observação de 37 plantas. Durante um período de um ano de observação, os cáudices cresceram, em média, 5,65 cm ano -1 , sendo que a taxa de crescimento se correlacionou fortemente com a altura das plantas. As taxas de produção de frondes novas (10,86 frondes ano -1 ) e de senescência (10,54 frondes ano -1 ), similares, evidenciaram capacidade de manter um número de frondes estável, no ano. Apenas 14 indivíduos desenvolveram frondes férteis, sendo que a maioria das plantas produziu esporos no verão, liberando-os no inverno. A produção e liberação de esporos foram mais influenciadas pela temperatura e fotoperíodo do que pela precipitação.Palavras-chave: auto-ecologia, fenologia, pteridófita arborescente, taxas de crescimento, xaxim ABSTRACT -(Caudex growth and fenology of Dicksonia sellowiana Hook. (Dicksoniaceae) in Southern Brazil). In Southern and Southeastern Brazil, the tree fern Dicksonia sellowiana Hook. still is illegally extracted from remnants forests for the use of its fibrous caudex cover, as well as for cultivation as an ornamental plant. In the present study the caudex growth, frond production, expansion and senescence as well as the formation and release of spores have been studied based on the observation of 37 plants. During an observation period of one year, the caudexes grew at an average of 5.65 cm year ) evidenced the capacity of maintaining a stable number of fronds throughout the year. Only 14 individuals developed fertile fronds, most of them producing spores during the summer and liberating them during the winter. Production and release of spores were influenced more by temperature and photoperiod rather than by rainfall.

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

“…It is likely that the variation of approximately 3.5 h in the photoperiod over the course of a year in the coastal region of Rio Grande do Sul, together with the direct effects of changes in temperature, triggers predictable physiological responses in several species (Marchioretto et al 2007), as was observed for C. corcovadensis in the present study, as well as and for C. atrovirens and Dicksonia sellowiana in the studies conducted by Schmitt et al (2009) and Schmitt & Windisch (2012), respectively. In a study of 16 fern species in a subtropical broadleaf forest in northeastern Taiwan, Lee et al (2009) reported that leaf senescence, spore maturation and spore release all presented significant positive correlations with temperature but not with precipitation, which is in agreement with our findings for C. corcovadensis.…”

“…The mean annual number of mature leaves was equivalent among the three years evaluated. Therefore, tree ferns seem able to maintain a relatively stable number of leaves over a long period of time, as observed for Dicksonia sellowiana (Schmitt et al 2009) and C. atrovirens (Schmitt & Windisch 2012).…”

“…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. ex Kuhn) Domin by Young & Leon (1989), in Peru; for A. setosa and C. delgadii by Schmitt & Windisch (2005;, as well as for Dicksonia sellowiana by Schmitt et al (2009), in southern Brazil.…”

“…(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.…”

“…However, seasonality in the phenology of tropical ferns occurs without welldefined rainfall seasonality (Schmitt & Windisch 2006a;Schmitt et al 2009), which suggests that other climatic factors, such as photoperiod and temperature, are important determinants of phenology, as observed by Chiou et al (2001) and Schmitt et al (2009). In addition to climatic variables, phenological events also result from biotic factors (van Schaik et al 1993), which include morphological aspects (Borchert 1983;Schmitt et al 2009), as well as the activity of herbivorous animals (Aide 1993).…”