931 resultados para Cerrado savanna
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Pós-graduação em Ciência Florestal - FCA
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Bauru: region of cerrado ou forest? The city of Bauru is located in São Paulo State, where the maps showing native vegetation distribution does not clearly defi ne its nature. In order to clarify which types of native vegetation was found in this region, a bibliographic survey was performed, ranging from ancient documents prepared by naturalists describing this region and recent research results of floristic and phytosociological character. It is concluded that in Bauru, semideciduous seasonal forests overlays the northwestern and that cerrado comes over the southeast region. In riparian areas where the cerrado prevailed, there are still traces of swamp forests and swamp grasslands. In the border areas between forests and cerrado, the occurrence of vegetation transition is common, with two distinct types of it and other typical of these ecotone zones.
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Pós-graduação em Ciência Florestal - FCA
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The aim of this study was to determine the effect of nitrogen (N) and the phosphorus (P) in seedlings of Amburana cearensis planted in areas occupied by Brachiaria decumbens, in an Oxisol, which originally had a Dense Savanna and in a Plinthic surrounding a Gallery Forest. We evaluated the response of A. cearensisgrowth and survival in the absence and doses of -1 10, 20 and 40 kg ha N, as urea and absence and doses of 10, 20 and -1 40 kg ha P, in the form of triple superphosphate in a randomized complete block design. We evaluated the stem diameter at four, eight and twelve months after planting. At the end of the first year were evaluated crown diameter and survival. According to the classification proposed in this study the growth of A. cearensis can be considered very slow in the Oxisol, regardless of fertilization, very slow when fertilized with N in the Plinthic and slow when fertilized with P. Despite the lower growth in Oxisol, the A. cearensis showed higher nutritional requirement there. The A. cearensis seedlings showed moderate nutritional requirement for N and high for P. In Plinthic, their nutritional requirement for P was moderate and total N present in the soil was sufficient to meet growth demand in this stage. This small nutritional requirement for N may be associated with its ability to nodulation.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Much effort has been devoted to understanding the function of extrafloral nectaries (EFNs) for antplantherbivore interactions. However, the pattern of evolution of such structures throughout the history of plant lineages remains unexplored. In this study, we used empirical knowledge on plant defences mediated by ants as a theoretical framework to test specific hypotheses about the adaptive role of EFNs during plant evolution. Emphasis was given to different processes (neutral or adaptive) and factors (habitat change and trade-offs with new trichomes) that may have affected the evolution of antplant associations. We measured seven EFN quantitative traits in all 105 species included in a well-supported phylogeny of the tribe Bignonieae (Bignoniaceae) and collected field data on antEFN interactions in 32 species. We identified a positive association between ant visitation (a surrogate of ant guarding) and the abundance of EFNs in vegetative plant parts and rejected the hypothesis of phylogenetic conservatism of EFNs, with most traits presenting K-values < 1. Modelling the evolution of EFN traits using maximum likelihood approaches further suggested adaptive evolution, with static-optimum models showing a better fit than purely drift models. In addition, the abundance of EFNs was associated with habitat shifts (with a decrease in the abundance of EFNs from forest to savannas), and a potential trade-off was detected between the abundance of EFNs and estipitate glandular trichomes (i.e. trichomes with sticky secretion). These evolutionary associations suggest divergent selection between species as well as explains K-values < 1. Experimental studies with multiple lineages of forest and savanna taxa may improve our understanding of the role of nectaries in plants. Overall, our results suggest that the evolution of EFNs was likely associated with the adaptive process which probably played an important role in the diversification of this plant group.
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Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.
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Some invasive grasses have been reported to change fire behavior in invaded plant communities. Urochloa brizantha is an aggressive invasive grass in the Brazilian Cerrado, an ecosystem where fire is a common disturbance. We investigated the effects of U. brizantha on fire behavior in an open Cerrado physiognomy in Central Brazil. Using experimental burnings we compared fire behavior at both the community and the individual plant level in invaded (UJ) and non-invaded (NJ) areas burned in July. We also assessed the effect of fire season in invaded areas by comparing July (UJ) and October (UO) burnings. We evaluated the following variables: fuel load, fuel moisture, combustion efficiency, maximum fire temperature, flame height, and fire intensity. Additionally, we evaluated the temperatures reached under invasive and native grass tussocks in both seasons. Fuel load, combustion efficiency, and fire intensity were higher in NJ than in UJ, whilst flame height showed the opposite trend. Fuel amount and fire intensity were higher in October than in July. At the individual plant level, U. brizantha moisture was higher than that of native species, however, temperatures reaching ≥600 °C at ground level were more frequent under U. brizantha tussocks than under native grasses. At the community level, the invasive grass modified fire behavior towards lower intensity, lower burning efficiency, and higher flame height. These results provide essential information for the planning of prescribed burnings in invaded Cerrado areas.
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Acknowledgments The authors are very grateful to Mr. Fabiano Bielefeld Nardotto, owner of the Tabapuã dos Pireneus farm, for allowing our free movement around the farm and collection of soil samples, as well as providing information about soybean cultivation. The authors also thank Dr. Plínio de Camargo, who performed the isotopic analysis in the CENA laboratory at the University of São Paulo (USP). This work was supported by grants from the National Council of Technological and Scientific Development (CNPq), Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES), and Foundation for Research Support of Distrito Federal (FAP-DF).
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2015.
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Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, Programa de Pós-Graduação em Ciências Florestais, 2016.