a b s t r a c tHigh descending winds generated by convective storms are a frequent and a major source of tree mortality disturbance events in the Amazon, affecting forest structure and diversity across a variety of scales, and more frequently observed in western and central portions of the basin. Soil texture in the Central Amazon also varies significantly with elevation along a topographic gradient, with decreasing clay content on plateaus, slopes and valleys respectively. In this study we investigated the critical turning moments (M crit -rotational force at the moment of tree failure, an indicator of tree stability or wind resistance) of 60 trees, ranging from 19.0 to 41.1 cm in diameter at breast height (DBH) and located in different topographic positions, and for different species, using a cable-winch load-cell system. Our approach used torque as a measure of tree failure to the point of snapping or uprooting. This approach provides a better understanding of the mechanical forces required to topple trees in tropical forests, and will inform models of wind throw disturbance. Across the topographic positions, size controlled variation in M crit was quantified for cardeiro (Scleronema mincranthum (Ducke) Ducke), mata-matá (Eschweilera spp.), and a random selection of trees from 19 other species. Our analysis of M crit revealed that tree resistance to failure increased with size (DBH and ABG) and differed among species. No effects of topography or failure mode were found for the species either separately or pooled. For the random species, total variance in M crit explained by tree size metrics increased from an R 2 of 0.49 for DBH alone, to 0.68 when both DBH and stem fresh wood density (SWD) were included in a multiple regression model. This mechanistic approach allows the comparison of tree vulnerability induced by wind damage across ecosystems, and facilitates the use of forest structural information in ecosystem models that include variable resistance of trees to mortality inducing factors. Our results indicate that observed topographic differences in windthrow vulnerability are likely due to elevational differences in wind velocities, rather than by differences in soil-related factors that might effect M crit .

O Laboratório de Engenharia da Madeira do Centro de Pesquisa de Produtos Florestais realizou inúmeros ensaios físicos e mecânicos, em madeiras originárias da areas a ser alagada na Hidroelétrica de Balbina. O presente trabalho pretende relatar o ensaio de flexão estática obedecendo aos seguintes passos: a) revisão bibliográfica sobre flexão estática, descrevendo além do método de calculo para determinação dos esforços, fatores que influem na resistência da madeira submetida à flexão; b) apresentação do ensaio de flexão estática, adotado pelo CPPF, divulgação dos dados experimentais e discussão sobre o tipo de ruptura que ocorrem nas madeiras do Amazonas; e c) estudo da relação entre módu lo de elasticidade a flexão, modulo de ruptura e densidade com os dados obtidos nos ensaios.

RESUMO: A utilização de novas tecnologias para caracterizar madeiras tropicais é essencial para reduzir desperdícios na cadeia produtiva da indústria madeireira, aumentando o rendimento e produtividade do setor. Objetivou-se neste trabalho avaliar a utilização da tomografia de impulso na identificação do estado de sanidade e rendimento do lenho de árvores na floresta. O estudo foi conduzido em 01 hectare na Estação Experimental de Silvicultura Tropical-Núcleo ZF-2-INPA. Foram selecionadas quatro árvores de Micrandopsis scleroxylon W. Rodr. para a utilização da tomografia de impulso; técnica essa que se baseia no cálculo da velocidade de propagação das ondas mecânicas no interior do lenho, originando uma imagem tomográfica. Utilizou-se a fórmula de Smalian para determinação dos volumes de madeira total e do oco, sendo sua diferença, o volume de madeira útil. Também foi estimado o volume de madeira útil a partir dos dados da tomografia de impulso. As árvores foram desdobradas na serraria para o cálculo do rendimento. Estes dados foram comparados com a classificação feita no software Envi 4.8, verificando a relação entre essas variáveis. A tomografia de impulso mostrou-se eficiente para estimar o estado de sanidade da árvore na floresta, demonstrando ser uma ferramenta útil no planejamento da exploração florestal. Palavra-chave: metodologia não destrutiva, manejo florestal, madeiras da Amazônia. Impulse tomography in the evaluation sanity and perfomance of Micrandopsis scleroxylon W. Rodr.

Studying and knowing the Amazon Rainforest in the current socioeconomic scenario leads to reflection on the effectiveness of the scientific methodologies adopted. Is the dialogue between research groups and decision makers allowing the production of knowledge robust and appropriate to the demands of the Amazonian productive sector, and articulated in order to sensitize the academy to focus on existing technological bottlenecks, as well as new opportunities for the use of natural wealth? An analysis was carried out on the requirements of scientific development notices produced by the main institutions of promotion and development in the Amazon Rainforest in the last two years, and it was found that the predominant epistemology is disciplinarity, a fact that makes the application of results more restricted. The temporal scale of scientific production, speed of impact on society in relation to its application, adequate language and lack of perception of society about the uncertainty of politics, are important factors that affect the relationship between academia and opinion makers and public policies, and it is necessary to intensify a certain scientific activism, application of translational epistemology. In parallel, the management of the governance of scientific knowledge would be, in some cases, more likely to succeed with the use of algorithms that are still timidly adopted in the academic environment of the Amazon Rainforest.

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