465 resultados para Stadiums phenological


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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There are strong uncertainties regarding LAI dynamics in forest ecosystems in response to climate change. While empirical growth & yield models (G&YMs) provide good estimations of tree growth at the stand level on a yearly to decennial scale, process-based models (PBMs) use LAI dynamics as a key variable for enabling the accurate prediction of tree growth over short time scales. Bridging the gap between PBMs and G&YMs could improve the prediction of forest growth and, therefore, carbon, water and nutrient fluxes by combining modeling approaches at the stand level.Our study aimed to estimate monthly changes of leaf area in response to climate variations from sparse measurements of foliage area and biomass. A leaf population probabilistic model (SLCD) was designed to simulate foliage renewal. The leaf population was distributed in monthly cohorts, and the total population size was limited depending on forest age and productivity. Foliage dynamics were driven by a foliation function and the probabilities ruling leaf aging or fall. Their formulation depends on the forest environment.The model was applied to three tree species growing under contrasting climates and soil types. In tropical Brazilian evergreen broadleaf eucalypt plantations, the phenology was described using 8 parameters. A multi-objective evolutionary algorithm method (MOEA) was used to fit the model parameters on litterfall and LAI data over an entire stand rotation. Field measurements from a second eucalypt stand were used to validate the model. Seasonal LAI changes were accurately rendered for both sites (R-2 = 0.898 adjustment, R-2 = 0.698 validation). Litterfall production was correctly simulated (R-2 = 0.562, R-2 = 0.4018 validation) and may be improved by using additional validation data in future work. In two French temperate deciduous forests (beech and oak), we adapted phenological sub-modules of the CASTANEA model to simulate canopy dynamics, and SLCD was validated using LAI measurements. The phenological patterns were simulated with good accuracy in the two cases studied. However, IA/max was not accurately simulated in the beech forest, and further improvement is required.Our probabilistic approach is expected to contribute to improving predictions of LAI dynamics. The model formalism is general and suitable to broadleaf forests for a large range of ecological conditions. (C) 2014 Elsevier B.V. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The best irrigation management depends on accurate estimation of reference evapotranspiration (ET0) and then selection of the appropriate crop coefficient for each phenological stage. However, the evaluation of water productivity on a large scale can be done by using actual evapotranspiration (ETa), determined by coupling agrometeorological and remote sensing data. This paper describes methodologies used for estimating ETa for 20 centerpivots using three different approaches: the traditional FAO crop coefficient (K-c) method and two remote sensing algorithms, one called SEBAL and other named TEIXEIRA. The methods were applied to one Landsat 5 Thematic Mapper image acquired in July 2010 over the Northwest portion of the Sao Paulo State, Brazil. The corn, bean and sugar cane crops are grown under center pivot sprinkler irrigation. ET0 was calculated by the Penman-Monteith method with data from one automated weather station close to the study site. The results showed that for the crops at effective full cover, SEBAL and TEIXEIRA's methods agreed well comparing with the traditional method. However, both remote sensing methods overestimated ETa according to the degree of exposed soil, with the TEIXEIRA method presenting closer ETa values with those resulted from the traditional FAO K-c method. This study showed that remote sensing algorithms can be useful tools for monitoring and establishing realistic K-c values to further determine ETa on a large scale. However, several images during the growing seasons must be used to establish the necessary adjustments to the traditional FAO crop coefficient method.

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The jambu belongs to the family Asteraceae, tropical crop, nowadays, this plant has been considered as a promising vegetable crop, because to its pharmacological properties. Despite this novelty, the vegetable remains invisible in the statistics of production and market in the state of Para, Brazil. This research was carried out with the aim of comparing the economic productivity and phenological development by the morpho-physiological growth indexes of two cultivars of jambu organic manure and mineral fertilizers. The experiment was carried out at the Sao Manuel Experimental Farm (Sao Manuel-SP), which belongs to the Faculdade de Ciencias Agronomicas - UNESP, campus Botucatu. The experimental design was a factorial randomized blocks (2 x 2) with two fertilization (organic and mineral) and two cultivars (Jambuarana and Nazareth), with six replications, two fertilization (organic and mineral) and two cultivars (Jambuarana and Nazareth). The following characteristics were evaluated: Plant height (cm), Leaf area (cm(2)), Fresh mass (g), Dry mass (g), Leaf area index (LAI), Leaf area ratio (LAR), Specific leaf Area (SLA), Leaf Weight Ratio (LWR), Amount of water in the plant (QAPA) (g per plant set), Leaf specific weight (LSW) (g cm(-2) per plant set) and Economic productivity. All data were statistically analyzed by analysis of variance and the Tukey test (1%) for mean comparison, with the software SISVAR. In the conditions of this experiment was carried out, it was possible to verify that the cultivar Jamburana had not only a good agronomic development and economic productivity under organic fertilization but also the best morpho-physiological indexes, showing that this kind of fertilization increases the agronomic effectiveness of this cultivar.

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Pós-graduação em Agronomia (Produção Vegetal) - FCAV

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Brazilian cerrado is characterized by an evident seasonality with distinct dry and wet seasons. Pyrostegia venusta is a common vine found in different physiognomies of the Cerrado. The species may present characteristics that allow its adjustment to the seasonal cycles. The phenology of vegetative and reproductive events was studied for this species in 2004 and 2005. The objective was to verify which climatic factors determine the phenological patterns observed in the species. Flowering was inversely related to mean temperatures and to the length of the day, while fruiting was inversely related to the photoperiod and directly related to the mean wind velocity. Seed dispersal was directly related to wind speed. As a consequence, flowering occurred at the end of the rainy season, close to the winter, and was prolonged until the end of the dry season. Fruiting and fruit maturation occurred during the dry period, with the seeds being dispersed at the end of this period. The seed dispersal at the end of the dry season, common to other anemochoric species of cerrado, allows a rapid germination at the beginning of the wet season, favoring the species propagation in this environment.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)