Resumo As mudanças climáticas são uma resposta da dinâmica do sistema Terra a fatores intrínsecos ou extrínsecos ao planeta. Importantes consequências dessa alteração climática são as ocorrências de secas ou do aumento na intensidade das chuvas em várias regiões do globo terrestre, que pode reduzir ou aumentar a disponibilidade de água no sistema. Para a Amazônia o cenário de severidade de secas pode se agravar, conforme sugerido por modelos climáticos. Neste sentido, o objetivo deste trabalho é analisar a anomalia de chuva e a tendência de precipitação para o período de 1994 a 2017 em sete estações pluviométricas localizadas na Amazônia Central e relacioná-los aos eventos interanuais/ interdecadais. Para tal, utilizou-se o índice de Anomalia de Chuva (IAC) e o teste não paramétrico de Mann-Kendall. Os resultados sugerem que somente El Niños extremos, tais como os de 1997 e 2015, apresentaram redução na precipitação em todas as estações, enquanto o La Niña de 1999 foi o que apresentou os maiores aumentos, a partir dos IACs. Com relação ao teste de tendências de Mann-Kendall, somente na estação C apresentou uma tendência de aumento na precipitação, evidenciando a necessidade de maiores séries temporais de precipitação para análises mais concisas.

Abstract Climate change is a response to the dynamics of the Earth system to intrinsic or extrinsic factors to the planet. Important consequences of this climate change are the occurrence of droughts or an increase in the intensity of rainfall in various regions of the globe, which can reduce or increase the availability of water in the system. For the Amazon, the drought severity scenario may worsen, as suggested by climate models. The purpose of this work is to analyze the rain anomaly and the precipitation trend for the period from 1994 to 2017 in seven pluviometric stations located in Central Amazonia and relate them to the events El Niño and La Niña. For this, the Rain Anomaly Index (RAI) and the Mann-Kendall non-parametric trend assessment test were used. The results suggest that only extreme El Niño, such as those in 1997 and 2015, showed a decrease in precipitation, while La Niña in 1999 was the one that showed the greatest increases, from the RAI. Regarding the Mann-Kendall trend test, only at station C it showed a tendency to increase in precipitation, showing the need for larger precipitation time series for more concise analyzes.

This research was aimed to evaluate the concentration of 15 chemical elements as a reference base for the quality of the litter in a forest in the central region of the Amazon. The sampling of the litter was performed monthly in two topographic positions for one year. For the quantification of the elements, digestion by nitroperchloric solution and reading by ICP OES were performed. The mean of macronutrient contents in the litter in decreasing order were Ca>K>Mg>Na. For micronutrients, the order was Al>Mn>Fe>Sr>Zn>Cu>Ba>Cr>Ni>Co>Cd for the Plateau and Al>Mn>Fe Sr>Zn>Cu>Ba>Cr>Ni>Cd>Co for the Baixio. Among the fractions, calcium had its highest concentration in the woody material, potassium in the reproductive material, while magnesium, sodium, and aluminum showed higher concentrations in the leaf fraction. Also, it was observed that the return of the elements to the soil by litter was greater in the dry period of the region, due to the greater fall in plant material. Calcium differed significantly within the same area, obtaining the highest concentrations compared to the other elements, while aluminum and zinc differed significantly between the areas studied, with a higher return for both elements on the Plateau.

Considering the size of the Amazon region and the need for studies to establish soil trace metal concentrations in natural environments, the objective of this work was to evaluate heavy metal contents in a toposequence of an Amazon State microbasin. Soil samples were collected in three native forest topographic positions. Samples were opened for analysis by two methods: exchangeable cations were determined by the silver thiourea method and total metal elements by sulfuric acid. The metals were determined by atomic absorption spectrometry. In general, it was observed low concentration of several elements considered essential to plant growth in the studied soils, indicating low concentration in the source material of these soils and the intense weathering leaching. The higher concentrations of heavy metals found in the Plateau / Shed areas may be related to clay soils and more acidic pH than other topographies. Exchangeable Al was found at higher concentrations, while Na was the element with the lowest concentration. Total metallic elements presented higher availability potential in the Plateau / Shed areas, except for B, Cr, Mo and Ni. These differences justify the development of regionalized studies for heavy metals in soils appropriate to the conditions of each environment.