Navegando por Assunto "Folhas"

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Acesso aberto (Open Access)
Atributos químicos do solo e composição química de folhas de mangue vermelho (Rhizophora mangle L.) em um manguezal e área transicional em São João de Pirabas, Pará
(Universidade Federal do Pará, 2015) NASCIMENTO, Bruno Delano Chaves do; RUIVO, Maria de Lourdes Pinheiro; http://lattes.cnpq.br/9419564604488031
Mangroves are characteristic coastal ecosystems of tropical and subtropical regions of great social and ecological importance. At Amazon these ecosystems represent more than half of mangrove areas of Brazil (about 70%) and are renowned for their great exuberance and magnitude related to regular distribution of rainfall, high temperatures, the large tidal range (> 4m) and the supply of sediments from the rivers of this region. Changes in water characteristics and physic-chemical soil properties can cause changes in nutrient dynamics in these ecosystems. In transitional environments these characteristics are altered and may have effects on the concentration of nutrients in the ecosystem compartments. In order to differentiate these transitional environments and the actual mangrove environments for the concentration of nutrients, this study aims to determine the nutrient content in the soil, in Rhizophora mangle L. leaves and leaf litter in these two types of environments in two seasonal periods, in a mangrove of the Amazon coast. Samples were collected in the drier month (September 2011) and in the rainy month (April 2012) in the two areas and subjected to chemical analysis for the concentration of macro (Ca, Mg, Na, K, Al, S, P, N, C) and micro nutrients (Cu, Zn, Mn, Fe). We also analyzed the physico-chemical properties of the soil (Eh, pH and salinity) and the granulometry of the ground. The results show higher nutrient concentrations in the fringe mangrove soil when compared to the transition zone (mangrove x secondary forest), indicating that the Eh, which is lower in the first influenced by the proximity to the sea and the highest frequency of flooding by tides, is the main differentiating factor in the concentration of soil nutrients. The nutrients in the Rhizophora mangle L. leaves not differ significantly from one environment to another and do not follow the same pattern of soil concentration on the two areas studied, however, the leaves nutrients are more influenced by the difference of a climatic period for other. Thus, the red mangrove trees of the transition zone can maintain a concentration of nutrients similar to the fringe of the forest, and the structural difference of the woods is more related to soil particle size than the nutritional relationship, since these trees have physiological mechanisms for the maintenance and selection of nutrients, such as N which could be a limiting nutrient in these environments.
Acesso aberto (Open Access)
Características morfogênicas, estruturais, acúmulo de forragem e composição química de capim-massai, submetido à adubação nitrogenada
(Universidade Federal do Pará, 2016-01-29) CUNHA, Antonio Marcos Quadros; RÊGO, Aníbal Coutinho do; http://lattes.cnpq.br/4330113577933018
The objective of this study was to evaluate the morphogenic, structural, biomass accumulation and chemical composition of plants of Massai grass submitted to six nitrogen doses (0, 100, 200, 300, 400 and 600 kg of N / ha / year) in a completely randomized design, with six replications in plots of 12 m². Urea was used as the Nitrogen source, whose doses were divided in six applications during the rainy season, according to the treatments. Forage harvesting was done at a residue height of 15 cm, when the canopy intercepted 95% of the incident light at an average of five internal points on the plot with the Accupar model LP-80® canopy analyzer. Data were submitted to variance analysis and regression, the significance level was 0.05 of the linear and quadratic coefficient and the coefficient of determination. There was (p<0.05) an increase in the rates of appearance, length and leaf senescence, as we as the number of alive leaves, number of matura leaves, percentage of stems and number of grazing cycles, all of them adjusted to a linear model. In contrast, the phyllochron, the duration of the leaf's life, the leaf blade/stem ratio and the rest days decreased, also linearly adjusted. The results for the accumulation of forage per cycle, daily forage accumulation, total forage accumulation and accumulation of dry leaf mass corresponded in quadratic form (p<0.05), the increase of nitrogen fertilization means a direct effect of the nitrogen flow in the tissues. There was a positive and linear effect of the nitrogen fertilization (p<0.05) for the crude protein and organic matter content. Negative effect (p<0.05) adjuted to a linear model for the dry matter and mineral content. No effect was observed (<0.05) for neutral detergent fiber, acid detergent fiber and hemicellulose, which limit the digestion. The nitrogen fertilization favors morphogenesis, forage production and the qualitative characteristics of Massai grass.