Fitossociologia de florestas de mangue plantadas e naturais no estuário do Rio das Ostras, Rio de Janeiro, Brasil

A fitossociologia de florestas de mangue plantadas e naturais foi comparada no estuário do Rio das Ostras, Rio de Janeiro, Brasil. A amostragem da vegetação foi feita pelo método de parcelas, sendo registrado o diâmetro à altura do peito (DAP) e a altura dos indivíduos > 1 m de altura. Os resultados indicaram que a floresta plantada apresenta menores valores de DAP médio e área basal, e maior densidade de troncos em relação à floresta natural. A distribuição de indivíduos por classes de altura e a distribuição de troncos por classes diamétricas mostraram que a floresta plantada é mais jovem. Laguncularia racemosa e Rhizophora mangle ocorreram em ambas as florestas, enquanto Avicennia schaueriana foi registrada apenas na floresta plantada. Laguncularia racemosa apresentou maior dominância e densidade relativa em todos os sítios analisados, provavelmente, por ser característica de locais com menor influência marinha e pelo fato do estuário ter sido alterado por perturbações antrópicas

Ecophysiology of two tropical species in an abandoned eucalyptus plantation: effect of plant litter removal and seasonality

http://dx.doi.org/10.5007/2175-7925.2015v28n2p27 O efeito da remoção da serapilheira sobre as variáveis do processo fotossintético (trocas gasosas, fluorescência da clorofila a, e conteúdo de pigmentos fotossintéticos) das espécies tropicais Xylopia sericea A. St.-Hil. e Siparuna guianensis Aubl. foi avaliado em um plantio abandonado de eucalipto (Corymbia citriodora (Hook.) K.D.Hill & L.A.S.Johnson (Myrtaceae)) durante os períodos chuvoso e seco, após 5 anos de remoção da serapilheira, na Reserva Biológica União, Rio de Janeiro, Brasil. A remoção da serapilheira não influenciou as respostas ecofisiológicas das espécies. Entretanto, significativa variação sazonal foi verificada. Durante o período seco, a concentração intercelular de CO2 (Ci ), a transpiração (E), e a condutância estomática (gs ) apresentaram redução nos valores, enquanto a eficiência intrínseca no uso da água (EIUA), a dissipação não-fotoquímica (NPQ) e os carotenoides aumentaram, resultado que sugere uma estratégia protetora contra estresse. No entanto, os valores de Fv /Fm (rendimento quântico máximo) e Fm /Fo (taxa de rendimento da fluorescência pelos estados aberto e fechado) indicam que, mesmo durante o período seco, não houve redução fotoquímica nas espécies. Apenas S. guianensis apresentou redução nos valores da taxa de fotossíntese líquida (A) durante o período seco. Os dados sugerem que X. sericea é fotossinteticamente mais eficiente sob condições de baixa disponibilidade de água e que a remoção da serapilheira por um período de 5 anos não promove diferenças nos processos ecofisiológicos das espécies analisadas.http://dx.doi.org/10.5007/2175-7925.2015v28n2p27The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a fluorescence, and content of photosynthetic pigments) of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalyptus (Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae)). The study was conducted at the União Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after five years of litter removal. The removal of plant litter did not influence the ecophysiological responses of the species. There was however significant seasonal variation. During the dry period, intercellular CO2 concentration (Ci), transpiration (E), and stomatal conductance (gs) were decreased, while intrinsic efficiency of water use (IWUE), non-photochemical quenching (NPQ), and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for Fv/Fm (maximum quantum efficiency) and Fm/Fo (ratio of fluorescence yields for open and closed states) indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A) during the dry period. The data indicated that X. sericea was photosynthetically more efficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed.

Ecophysiology of two tropical species in an abandoned eucalypt plantation: effect of plant litter removal and seasonality

The effect of the removal of plant litter on photosynthetic variables (gas exchanges, chlorophyll a fluorescence, and content of photosynthetic pigments) of the tropical species Xylopia sericea A. St.-Hil. and Siparuna guianensis Aubl. was evaluated in an abandoned plantation of eucalypt (Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae)). The study was conducted at the União Biological Reserve, Rio de Janeiro State, Brazil during the rainy and dry periods, after five years of litter removal. The removal of plant litter did not influence the ecophysiological responses of the species. There was however significant seasonal variation. During the dry period, intercellular CO2 concentration (Ci), transpiration (E), and stomatal conductance (gs) were decreased, while intrinsic efficiency of water use (IWUE), non-photochemical quenching (NPQ), and carotenoid values increased, suggesting a protective strategy against stress. Nevertheless, the values for Fv/Fm (maximum quantum efficiency) and Fm/Fo (ratio of fluorescence yields for open and closed states) indicated that even during the dry period there was no reduction in photochemical activity in these species. Only S. guianensis exhibited a reduced net photosynthetic rate (A) during the dry period. The data indicated that X. sericea was photosynthetically more efficient under conditions of low water availability and that a 5-year period of plant litter removal failed to produce differences in ecophysiological processes in the species analyzed

Phytosociology of planted and natural mangrove forests in the estuary of the Ostras River, Rio de Janeiro State, Brazil

The phytosociology of planted and natural mangrove forests were compared in the estuary of the Ostras River, Rio de Janeiro State, Brazil. Vegetation sampling was performed by the plot method, and the diameter at breast height (DBH) and height of individuals > 1 m tall were recorded. The results indicated that the planted forest had lower average DBH and basal area and higher density of trunks in relation to natural forest. The distribution of individuals by height class and the distribution of stems per diameter class showed that the planted forest was younger. Laguncularia racemosa and Rhizophora mangle occurred in both forests, while Avicennia schaueriana was found only in the planted forest. Laguncularia racemosa showed greater dominance and relative density at all sites analyzed, probably because it is characteristic of sites with less marine influence and the fact that the estuary had been altered by human disturbance

Chlorophyll a fluorescence and ultrastructural changes in chloroplast of water hyacinth as indicators of environmental stress

Chlorophyll a fluorescence parameters and transmission electron microscopy (TEM) were used to assess the stress conditions in water hyacinth along the Paraiba do Sul River (PSR), an important River in southeastern Brazil. The data were obtained at the end of the dry season of 2005 and at the end of the wet season of 2006. Changes in F-o and F-m parameters were observed as differentiated responses, depending on the season. Non-photochemical dissipation (qN and NPQ) from plants was greater in the most industrialized region of the PSR in both seasons. However, F-v/F-m for all samples ranged between 0.77 and 0.81, showing that high maximum quantum yield was maintained. Although the F-v/F-m suggests that the plants were exhibiting normal photochemical activities, ultrastructural changes in chloroplasts showed thylakoids disorganization. Plants from the most industrialized region showed non-stacking grana thylakoids disposition. In spite of these alterations, the membrane integrity was maintained, suggesting an adaptation to adjustment to adverse environmental conditions. (C) 2008 Elsevier B.V. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2004/15012-5]Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[471091/2004-9]Universidade Estadual do Norte Fluminens

Structural and ecophysiological alterations of the water hyacinth [Eichhornia crassipes (Mart.) Solms] due to anthropogenic stress in Brazilian rivers

In this work, the structural and ecophysiological alterations (chlorophyll a fluorescence and photosynthetic pigments), and quantification of Cr, Pb and Zn in the leaf limb, petiole and younger and older roots of water hyacinth from the lower, medium and upper Paraíba do Sul river (PSR) and Imbé river were evaluated. The plants from the medium and upper PSR (more industrialized and populated regions) exhibited lower turgid cell in the root cortex, less root hairs and leaf epidermis, chloroplasts with plastoglobules and increased stroma volume. Higher concentrations of metals were observed in the younger and older roots from the medium PSR plants. The results suggested that the plants from more anthropized regions were able to maintain the maximum quantum yield (Fv/Fm) which was a result from the metabolic fitting, increasing the non-photochemical quenching, reducing total chlorophyll/carotenoids and leading to the structural modifications

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved