Sobrevivência e crescimento inicial de Ocotea pulchella (Lauraceae) em uma floresta de restinga da Ilha do Cardoso, SP
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Data
2012-12-01
Autores
Pires, Luciana Andréa
Cardoso, Victor José Mendes [UNESP]
Rodrigues, Ricardo Ribeiro
Joly, Carlos Alfredo
Título da Revista
ISSN da Revista
Título de Volume
Editor
Instituto de Pesquisas Jardim Botânico do Rio de Janeiro
Resumo
Neste trabalho, avaliou-se os efeitos de fatores ambientais na sobrevivência e crescimento inicial de Ocotea pulchella (Nees) Mez numa floresta de restinga. Os ensaios consistiram do plantio de mudas classificadas em dois grupos de idade (plântulas e juvenis) em diferentes áreas selecionadas quanto à cobertura vegetal (clareiras ou sub-bosque) e umidade do solo (secos e úmidos). As plantas de ambas as idades apresentaram a maior taxa de mortalidade no sub-bosque úmido, onde se observou os valores mais baixos de luz fotossinteticamente ativa e fertilidade do solo. A sobrevivência de plântulas correlacionou-se positivamente ao crescimento, que por sua vez, foi favorecido em clareiras, sugerindo uma dependência da espécie em relação a ambientes mais iluminados, embora essa possa ocupar o sub-bosque em fisionomias mais abertas como as restingas. em juvenis, a sobrevivência foi relacionada principalmente aos fatores edáficos; o crescimento em altura foi muito baixo, não sendo constatado incremento significativo de área foliar nem de matéria seca em nenhum dos ambientes, o que pode estar relacionado ao caráter oligotrófico do solo. Os juvenis em sub-bosque de solo úmido apresentaram ao final do experimento os menores valores de altura, área foliar, razão de área foliar, razão de massa foliar e taxa de assimilação líquida, sugerindo que baixas irradiâncias associadas a solos saturados e quimicamente pobres podem restringir o recrutamento da espécie no local estudado. Todavia, o comportamento de certa forma generalista para as condições de luz e umidade do solo, indica uma alta capacidade de O. pulchella em colonizar distintos micro-ambientes da restinga, onde se observa uma grande variação espaço-temporal de fatores ambientais.
The aiming of this work was to evaluate the effects of environmental factors on both the survival and initial growth of Ocotea pulchella (Nees) Mez at a restinga forest. The tests consisted of transplanting seedlings classified into two age groups (seedlings and juveniles) in different areas selected as for plant covering (gaps or understorey) and soil moisture (dry or wet). Both seedlings and juveniles presented the highest mortality rate when they were planted in the 'wet understorey', in which the lowest soil fertility and irradiance levels were recorded. Seedling survival correlated positively with growth, which was promoted in gaps, suggesting a dependence of the species on more lighted environments, although O. pulchella can occupy the understorey in more open physiognomies such as restinga forest. The juveniles survival correlated mainly with edaphic factors; the growth in height was very low and no significant increase in leaf area and dry weight was observed in any of the environments, what can be related to the oligotrophic characteristics of the soil. Juveniles planted in 'wet understorey' presented the lowest height, leaf area, leaf area ratio, leaf mass ratio and net assimilation rate values, suggesting that the species recruitment in the restinga can be reduced in environments with low irradiances and waterlogged soils. However, the somehow generalist character of the species in response to irradiance levels and soil moisture may suggest a high ability of O. pulchella in colonizing distinct micro-environments at restinga, in which environmental factors may fluctuate greatly over time and space.
The aiming of this work was to evaluate the effects of environmental factors on both the survival and initial growth of Ocotea pulchella (Nees) Mez at a restinga forest. The tests consisted of transplanting seedlings classified into two age groups (seedlings and juveniles) in different areas selected as for plant covering (gaps or understorey) and soil moisture (dry or wet). Both seedlings and juveniles presented the highest mortality rate when they were planted in the 'wet understorey', in which the lowest soil fertility and irradiance levels were recorded. Seedling survival correlated positively with growth, which was promoted in gaps, suggesting a dependence of the species on more lighted environments, although O. pulchella can occupy the understorey in more open physiognomies such as restinga forest. The juveniles survival correlated mainly with edaphic factors; the growth in height was very low and no significant increase in leaf area and dry weight was observed in any of the environments, what can be related to the oligotrophic characteristics of the soil. Juveniles planted in 'wet understorey' presented the lowest height, leaf area, leaf area ratio, leaf mass ratio and net assimilation rate values, suggesting that the species recruitment in the restinga can be reduced in environments with low irradiances and waterlogged soils. However, the somehow generalist character of the species in response to irradiance levels and soil moisture may suggest a high ability of O. pulchella in colonizing distinct micro-environments at restinga, in which environmental factors may fluctuate greatly over time and space.
Descrição
Palavras-chave
plântula, regeneração, microambiente, Ilha do Cardoso, restinga, seedling, regeneration, micro-environment, Ilha do Cardoso, sandy coastal plane
Como citar
Rodriguésia. Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, v. 63, n. 4, p. 763-774, 2012.