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Fósforo (P) e potássio (K) são macronutrientes essenciais às plantas e aos animais. Em ambientes aquáticos contaminados por esgotos domésticos e industriais, esses nutrientes podem causar sérios problemas. O fosfato (P-PO43-), na forma solúvel, representa uma fonte interna de fósforo para o crescimento de algas, e a ingestão de água com excesso de K pode provocar graves efeitos laxantes. Dessa forma, o presente trabalho tem como objetivo avaliar correlação linear entre esses dois parâmetros usando o método de correlação de Pearson (R) em amostras de água coletadas na Bacia Hidrográfica do Educandos (Manaus-AM). Em estudos de monitoramento, esse conhecimento se faz importante para estabelecer as principais variáveis que influenciam nos níveis de contaminação dos igarapés na Bacia Hidrográfica do Educandos.

As preocupações mais difundidas com relação à contaminação por dejetos humanos e animais são causadas por patógenos relacionados a doenças transmitidas pela água e concentrações excessivas de nitrogênio e fósforo que provocam o fenômeno da eutrofização. Dessa forma, esse estudo teve por objetivo avaliar a interação entre a bactéria E. Coli com os teores de fosfato em uma bacia hidrográfica urbana em Manaus. Foram realizadas 14 coletas quinzenais entre os meses de setembro de 2021 e março de 2022. As amostras de água para análise de E. coli foram coletadas próximos da superfície em frascos de vidro de 100 mL, enquanto que para as análises de fosfato, as amostras foram coletadas em frascos de polietileno e acondicionadas até as análises por Colilert e espectrofotometria, respectivamente. Os resultados mostraram que as águas naturalmente ácidas de Manaus apresentaram valores de pH básicos em muitos locais (até 7,20) e que existe uma tendência linear entre fosfato e E. coli. Esse microrganismo prevaleceu em ambientes menos ácidos. Em valores de pH próximos a 7,0 a concentração de fosfato praticamente não muda, como se esse íon estivesse associado a algum tampão no meio (a partir de 0,04 mg L-1). A E. coli predominou em todos os pontos cujas concentrações de fosfato foram acima de 0,04 mg L-1, obedecendo uma tendência logarítmica típica para crescimento de microbiano. Ao contrário do que se esperava, não houve diluição em direção às fozes desta bacia hidrográfica, nem para fosfato e nem para a E. coli.

A Física é uma área de grande alcance na sociedade moderna, contudo, há pouca aplicação em diagnósticos ambientais usando somente variáveis físicas. Diante desse disso, o presente estudo teve por objetivo avaliar três variáveis físicas (temperatura, condutividade elétrica e turbidez) em uma bacia hidrográfica urbana localizada no centro do polo industrial de Manaus – A Bacia Hidrográfica do Educandos – BHE. Foram selecionados nove pontos na BHE e as amostras de águas foram coletadas na superfície dos corpos de águas em frascos de polietileno. As amostras foram conduzidas ao laboratório de Química Ambiental do Instituto Nacional de Pesquisas da Amazônia – INPA. A temperatura da água foi determinada no campo com um termômetro de mercúrio. Condutividade elétrica e turbidez foram analisados por métodos eletroquímicos, com instrumentos de bancada. Os resultados mostraram valores de temperatura acima de 30° C o que sugere falta de arborização nas margens dos corpos de água, valores estes mais elevados que há duas décadas. A condutividade elétrica apresentou valores acima de 400 µS cm-1 o que denota a grande quantidade de eletrólitos lançados nesses ambientes, caracterizados naturalmente como pouco condutivos, e a turbidez elevada sugere solos revolvidos nas margens. A única exceção foi o ponto P1, que ainda guarda as condições físicas naturais desta bacia hidrográfica.

The variability of the molecular composition of dissolved organic matter (DOM) in soils is predominantly explained by microbial mineralization and assimilation as well as interactions with mineral surfaces and soil organic matter (SOM). From a temperate site with calcareous soil it is established that the molecular composition of DOM shifts from plant-derived towards microorganism-derived signals in soil depth profiles. This variability is largely explained by microbial activity and only to a minor degree by soil-derived parameters like texture and SOM. Here we analyze the molecular composition of DOM in depth profiles of tropical rainforest soils in order to compare its variability to the temperate site as the tropical ecosystems have larger variability in soil texture and mineralogy and lower SOM content. We collected porewater in soil profiles of four ecosystems belonging to two major Amazon rainforest types, terra firme forest on clay soils and white-sand forest on sandy soils. We analyzed the molecular composition of DOM using solid-phase extraction and ultrahigh resolution mass spectrometry.The concentration and composition of DOM differed strongly between the sandy white-sand and clayey terra firme sites. DOM concentration in white-sand soils was much higher and decreased less with depth compared to the terra firme forests. Topsoil DOM in white-sand forests was characterized by high abundance of aromatic plant-derived compounds, whereas it reflected a stronger microbial imprint in terra firme sites. The molecular composition of DOM changed significantly with depth at all sites. In both terra firme and one white-sand forest the transformation was consistent with the expected shift from plant-derived signals towards increasing microbial reworking. The Bray-Curtis dissimilarity between topsoil and greater depth was considerably higher in terra firme compared to white-sand soils with values of 0.32 +- 0.06 and 0.14 +- 0.04, respectively, suggesting much slower DOM transformation in sandy soils. The dissimilarity was correlated similarly to pH, clay content and mineralogy (Pearson R2 = 0.27, 0.21 and 0.23, respectively). The high dissimilarity in the terra firme sites that vary strongly in clay content and mineralogy was only significantly correlated to pH (R2 = 0.16). This suggests that clay content and mineralogy, likely linked to DOM adsorption, were less important for the observed depth trend, which aligns with results from the temperate site. The significant effect of soil pH on the molecular transformation is in line with the importance of microorganisms for DOM transformation as soil pH is a major control on microbial community structure. Overall, our results suggest that similar processes control DOM transformation in temperate and tropical ecosystems, which are likely linked to microbial processing and formation of DOM.

The research carried out consisted of a field survey upstream of the Lago Amazônico area and close to the Ecological Effluent Treatment Station (ETEE) of the National Institute for Research in the Amazon - INPA. The objective of the study was to detect possible impacts on the quality of groundwater due to the ETEE and the waters of Lago do Bosque da Ciência, which requires knowledge of the direction of groundwater flow at the site. The geophysical resistivity method, through the technique of vertical electrical sounding with the Schlumberger arrangement, was applied with the purpose of defining the depth of the top of the saturated zone in the study area as well as detecting possible impacts of the effluents of the treatment plant in subsurface. The resistivity method, through measurements by equipment placed on the surface, determines the electrical resistivity of the materials and their subsurface contrasts at different depths. In the area, three piezometers were installed, which enabled the calibration of the interpretation of the results of vertical electrical sounding. The survey of geophysical data provided a volume of information about the subsurface situation of the layout, lithological content and the depth of the water level of the subsurface layers through the seven vertical electrical surveys carried out around the INPA Lake and close to the ETEE. The results of the interpretation of the vertical electrical sounding and water level depth measurements in the piezometers were integrated to produce a potentiometric map to understand the hydrogeological behavior from the point of view of underground flow. The electrical resistivity values, relatively high in the study area, attribute a predominantly sandy lithological constitution, a result that is consolidated with the lithological description of the piezometers. The top of the saturated layer around the lake is deeper compared to the lake, causing its waters to seep into the aquifer. This is because the lake is artificial, constantly receiving water to maintain its level. The potentiometric map indicates a practically radial flow direction, with a slight inclination towards the north. The electrical surveys carried out near the treatment plant showed lower resistivity values, which may be related to the influence of effluents in the subsurface. The study was carried out with resources provided for in Law No. 8,387 and in accordance with Article 21 of Decree 10,521 / 2020 - INPA / SAMSUNG Partnership.

O igarapé do Quarenta é um importante corpo de água que cruza a cidade de Manaus, no Amazonas. Durante muito tempo, esse corpo hídrico representou fontes de lazer e de paisagismo para a região. No entanto, hoje representa uma lixeira a céu aberto no meio da cidade de Manaus. O objetivo desse estudo foi avaliar variáveis ambientais das águas do igarapé do Quarenta usando a quimiometria, a partir da HCA e da PCA em cinco pontos do igarapé do Quarenta que cruzam o polo industrial de Manaus. Os resultados motraram altos teores de amônio, muito acima do permitido e com altas taxas dos metais Fe e Mn. O pH das águas está alterado em pelo menos duas unidades, variando de ácido à básico em três décadas e os valores de condutividade elétrica estão pelo menos cinco vezes acima do natural. A HCA mostrou importantes associações entre amônio e pH, o que sugere que esse íon pode estar sendo o agente tamponante dessas águas degradadas. Outra associação importante foi a observada entre condutividade elétrica e HCO3-. A PCA confirmou essa última associação e mostrou que a alcalinidade, expressa em HCO3- pode ser a variável mais sensivel no conjunto de dados, dando a entender que a condutividade elétrica pode ser aumentada a partir do aumento da alcalinidade.

A recarga é um elemento-chave do ciclo hidrológico, sendo indispensável para a gestão integrada dos recursos hídricos. Este estudo objetivou quantificar e comparar as taxas de recarga direta de um aquífero freático localizado em uma região de floresta primária contígua a Manaus utilizando os métodos balanço hídrico (BH), variação do nível da água (VNA) e estimativa darcyana (ED). Foram obtidos dados de precipitação e temperatura atmosférica de 2013 a 2015 da estação meteorológica localizada na Reserva Florestal Adolpho Ducke (RFAD). Medições de nível da água subterrânea e ensaios para determinação de condutividade hidráulica foram executados em sete piezômetros instalados em microbacia de drenagem da RFAD. A vazão específica (Sy) foi determinada em amostras de solo indeformadas. Os resultados do método do BH indicam taxa de recarga de 47% (1.583 mm) em 2013, de 46% (1.277 mm) em 2014 e de 20% (680 mm) em 2015. A precipitação em 2014 foi 18% menor do que em 2013, e a de 2015 foi 21% menor do que em 2014, por causa do fenômeno El Niño, gerando redução significativa da recarga apenas no último ano. Os registros de nível da água subterrânea para ED foram feitos entre fevereiro e julho de 2013, gerando estimativa de recarga de 28% (624 mm) da precipitação. Aplicando-se o método de VNA foi estimada uma taxa de recarga de 52% (2.229 mm) para o período de fevereiro de 2014 a agosto de 2015. Os resultados indicam maior consistência entre BH e VNA. As taxas de recarga aqui obtidas são superiores às determinadas em situações hidrogeológicas análogas em outras regiões do país.

The most populous city of the world’s largest watershed (Manaus, Amazon Basin, Brazil) is experiencing an extensive urban expansion since the early 1970s, with an attendant cost in environmental degradation. The upland area of the Manaus municipality is characterized by several streams. In this work, we aim to gradually measure the anthropogenic effect on water quality: we monitored three streams flowing over three zones: a preserved (where the streams take source), a peri-urban (where rural and leisure activities occur), and an urban area. From June 2013 to May 2015, we characterized the water quality of these streams. Statistical analyses reveal peri-urban activity does not significantly impact the water quality. Indeed, when the disturbance remains space-, time- and intensity-limited, the streams have the capacity to assimilate the anthropogenic pollution. However, looking at a seasonal finer scale, peri-urban activity slightly affects the natural pattern of water quality, but these changes remain moderated when compared to the original pattern of water quality. Over urban area, the water quality presents significant higher alkalinity, mineralization, turbidity, suspended material, biochemical and chemical oxygen demands, and lower acidity and dissolved oxygen. These alterations originate with sewage deficiency, presence of landfill sites, enhanced leaching of upturned soil and domestic waste. The natural seasonal patterns of water quality are totally disturbed (inversion, intensification) in the urban area. During the wet season, enhanced rainfall in conjunction with human activity generates local seasonal processes of dilution (e.g. negative anomalies for most of the dissolved elements) and concentration (positive Mg and Fe anomalies). The latter can be linked with enhanced leaching during the rainy period (positive Mg and Fe anomalies) and nitrification activity in the urban area (positive NO3 and negative NH4 anomalies).

SPACE-TEMPORAL BIOGEOCHEMISTRY OF THE LITTER IN A NATURAL FOREST ENVIRONMENT IN THE CENTRAL AMAZON. 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.

Tropical rivers such as the Rio Negro constitute a major portion of the global aquatic flux of dissolved organic carbon (DOC) entering the ocean, but the exact amount, source contributions and fate of terrestrial DOC remain unknown. We investigated the role of valley and upland whitesand ecosystems (WSEs) and terra firme plateaus in forming blackwater tributaries in the Rio Negro basin to develop novel constraints for the terrestrial export of carbon. 5709 molecular markers from ground- and surface waters of two contrasting valley and upland sites feeding Rio Negro tributaries were identified by ultrahigh resolution mass spectrometry (FT-MS), analyzed by multivariate statistics and compared to known Rio Negro markers. In a Principal Coordinates Analysis, valley and upland DOC molecular composition differed by 78% from plateau DOC, which was characterized by reworked, aliphatic and unsaturated N- and S-containing molecules, while valley and upland DOC contained mainly condensed aromatics, aromatics and oxidized unsaturated structures. Valley and upland samples differed by 10% in molecular DOC composition and by their isotopic content (14C of SPE-DOC, 18O and 2H of water) which indicated differences in hydrology and C turnover. Against expectation, markers of widespread whitesand valleys did not emerge as a major source of Rio Negro markers, but specific upland markers did. Pubchem suggested chromene and benzofuran structures as promising candidates for further study. Our findings indicate that the export of molecular markers diverges from expected transport-limited DOC behavior, and thereby opens new avenues for source annotation beyond DOC quantity. Terrestrial DOC from upland whitesand areas is a major source of specific blackwater molecules missing in the regional ecosystem C balance, whereas C export from the whitesand valleys and especially from terra firme plateaus represents mainly recycled and transformed carbon not directly affecting the ecosystem C balance and possibly, the watersheds downstream molecular signature. Our study highlights the potential of high-resolution techniques to constrain carbon balances of ecosystems and landscapes by novel molecular markers. A comparison with other terrestrial DOM datasets indicated molecular similarities with temperate acidic soils and tropical rivers that warrant further analysis of common DOM markers. Implications, limitations, and future challenges are discussed in the light of potential applications of diagnostic molecular links for DOC source annotation and estimation of terrestrial DOM export in the land-to-ocean continuum., Geochimica et Cosmochimica Acta, 311, ISSN:0016-7037, ISSN:1872-9533

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.

Author(s): Negron-Juarez, R; Ferreira, SJF; Mota, MC; Faybishenko, B; Monteiro, MTF; Candido, LA; Ribeiro, RP; de Oliveira, RC; de Araujo, AC; Warren, JM; Newman, BD; Gimenez, BO; Varadharajan, C; Agarwal, D; Borma, L; Tomasella, J; Higuchi, N; Chambers, JQ | Abstract: Soil moisture plays a key role in hydrological, biogeochemical, and energy budgets of terrestrial ecosystems. Accurate soil moisture measurements in remote ecosystems such as the Amazon are difficult and limited because of logistical constraints. Time domain reflectometry (TDR) sensors are widely used to monitor soil moisture and require calibration to convert the TDR's dielectric permittivity measurement (Ka) to volumetric water content (θv). In this study, our objectives were to develop a field-based calibration of TDR sensors in an old-growth upland forest in the central Amazon, to evaluate the performance of the calibration, and then to apply the calibration to determine the dynamics of soil moisture content within a 14.2-m-deep vertical soil profile. Depth-specific TDR calibration using local soils in a controlled laboratory setting yielded a novel Ka–θv third-degree polynomial calibration. The sensors were later installed to their specific calibration depth in a 14.2-m pit. The widely used Ka–θv relationship (Topp model) underestimated the site-specific θv by 22–42%, indicating significant error in the model when applied to these well-structured, clay-rich tropical forest soils. The calibrated wet- and dry-season θv data showed a variety of depth and temporal variations highlighting the importance of soil textural differentiation, root uptake depths, as well as event to seasonal precipitation effects. Data such as these are greatly needed for improving our understanding of ecohydrological processes within tropical forests and for improving models of these systems in the face of changing environmental conditions.

The geological diversity of the Amazon Basin, as well as the pluvial regime, influences the characteristics of the waters. To know the water types of the rivers of the Amazon basin, 288 superficial water samples were collected, 94 of them along the Amazon River and 194 in their tributaries, from March 2009 to September 2012. The physical, chemical, and physicochemical properties were analyzed. Rivers with pH between 6.5 and 7.6 and electrical conductivity (40.00 - 80.00 μS cm-1) are water bodies that are influenced by the Andean region (e.g., the Amazon River and some of its right bank tributaries). On the other hand, the rivers with pH in the range of 3.5 to 5.5 and conductivity

Neste estudo, a experimentação e a modelagem hidrológica de eventos de precipitação transformada em escoamento superficial em sistemas naturais de floresta são investigadas, contemplando os seguintes tratamentos: construção de algoritmo computacional iterativo de otimização para a identificação do hidrograma unitário médio (função de transferência chuva-descarga) da bacia e para o cálculo das precipitações efetivas adequadas à cada evento chuva-escoamento; aplicação da metodologia à bacia hidrográfica do igarapé Bolívia, situada no interior da Reserva Florestal Adolpho Ducke; análise e interpretação do algoritmo criado, enfocando a sua convergência e o significado dos resultados desse processo de otimização; e comparação com outros estudos em pequenas bacias da Amazônia Central. O período de medidas de chuva e de vazões estende-se de julho de 2004 a setembro de 2006, incluindo a fase de preparação da curva-chave do igarapé Bolívia e a formação de um conjunto amplo e diversificado de eventos de chuva e de escoamento no curso d'água. In this study, experimentation and hydrologic modeling of rainfall events transformed into runoff in natural forest systems, are investigated, including the following treatments: construction of an iterative optimization computational algorithm to identify the average unity hydrograph (rain-discharge transfer function) of the watershed, and to compute the effective rainfalls adequate to each discharge-rainfall event; applying the methodology to the Igarapé Bolívia watershed, which is located inside the Adolpho Ducke Forest Reserve; analysis and interpretation of the established algorithm, focusing on its convergence and on the significance of the results of this optimization process; and comparison with other studies in small watersheds of Central Amazonia. Rainfall and runoff measurements were made from July 2004 to September 2006, including the preparation phase of the level-discharge curve of the Igarapé Bolívia and the making of a large and diversified set of rainfall and runoff events.

Os solos de terra firme da Amazônia Central, na sua maioria, são ácidos, pobres em nutrientes e a manutenção da floresta sobre esses solos é garantida pela ciclagem de nutrientes, praticamente fechada. A substituição de floresta por pastagens ou outras atividades agrícolas leva à diminuição de nutrientes do compartimento biomassa, podendo comprometer os processos de ciclagem no solo, pois plantas absorvem nutrientes que presentes na solução do solo. Para entender o efeito de retirada de árvores, foi realizado um estudo em uma área de floresta de terra firme na Amazônia Central submetida à extração seletiva de madeira (6-10 árvores, ou 34 m³ ha-1 de madeira) localizada 80 km ao norte de Manaus, foram determinados os teores NO3-, NH4+, K+, Ca2+, Mg2+ e Na+ na solução do solo na camada de 0-30 cm. O experimento constou de três blocos, cada um contendo uma parcela controle e uma que sofreu o corte seletivo de árvores, todos sobre um Latossolo Amarelo álico de textura muito argilosa. As medidas foram realizadas durante 13 meses, em cinco tratamentos em cada bloco: controle (floresta intacta), centro de clareira, borda de clareira, borda da floresta remanescente e floresta remanescente. Os teores de potássio, cálcio, magnésio e sódio mostraram diferenças significativas entre os tratamentos. As quantidades dos íons amônio e nitrato foram as menos afetadas. Os valores mais elevados foram geralmente encontrados nos tratamentos centro de clareira e borda de clareira. A maior diferença ocorreu na quantidade de sódio na solução do solo, que chegou a mais de 5 kg ha-1, no centro de clareira de dois blocos, praticamente o dobro da encontrada nas suas respectivas parcelas controles. As concentrações mais baixas dos nutrientes na solução do solo da floresta intacta (controle) e da floresta remanescente, confirmam a eficiência da floresta na ciclagem de nutrientes. Porém, no centro de clareira, além da remoção de árvores, a disponibilidade de materiais de fácil decomposição, como raízes mortas e a liteira acumulada, podem ter contribuído para uma maior concentração de nutrientes na solução do solo.

We examined the effects of mixed planting of fast growing tree species with indigenous Amazon tree species and soil tillage practices on soil physical properties in a deforested site used for agricultural cultivation. The site was located in the Central Amazon and consisted of Ferralsols. Bulk density and soil hardness were compared in the mixed planting site and an area where only indigenous tree species were planted. Many roots of the fast growing trees penetrated into the profile and caused changes in soil physical properties, i.e., decreasing bulk density and hardness. When tillage practices prior to planting were combined with mixed planting, the changes in soil physical properties were enhanced and the growth of not only the planted fast growing trees but also indigenous species such as mahogany, Swietenia macrophylla, which is shade tolerant, was accelerated.

Em uma área de floresta de terra firme na Amazônia Central submetida à extração seletiva de madeira (6-10 árvores ou 34 m³ ha-1 de madeira), foram medidas a precipitação interna e a interceptação da água da chuva num período de mais de dois anos. No primeiro ano, os dados coletados foram contínuos; no ano seguinte, as informações foram obtidas em campanhas intensivas em diferentes épocas do ano. Procurou-se quantificar as alterações produzidas pela extração seletiva na precipitação interna e na interceptação da chuva e, conseqüentemente, no ciclo hidrológico. Na floresta intocada (controle), a precipitação interna variou de 74,2 a 87,1 % e nas parcelas manejadas de 86,9 a 92,9%, verificando-se um aumento na precipitação interna após a extração seletiva de madeira. No entanto, as alterações provocadas pela extração seletiva na precipitação interna, que é a transferência de água da atmosfera para o solo após percolar o dossel da floresta, não foram estatisticamente significativas. Mas a interceptação da chuva, uma das partes do ciclo hidrológico, que retorna para a atmosfera e contribui para novas chuvas, foi significativamente alterada pela extração seletiva, provocando uma diminuição da quantidade de água retida pelo dossel. Throughfall and rainfall interception were measured during a 2-year period in forest submitted do selective logging (6-10 trees or 34 m³ ha-1 of timber). In the first year data were collected continuously; in the following year, data were obtained during intensive campaigns at different seasons. The goal was to quantify the changes produced by selective logging, both on throughfall and rainfall interception, and consequently in the forest hydrological cycle. The internal throughfall varied from 74.2 to 87.1%, in the pristine forest area (control), to 86.9 - 92.9%, in the managed plots, after selective logging. However, the changes in internal throughfall, which is the water transfer from the atmosphere to soil after percolating the forest canopy, due to the selective logging, were not significant. On the other hand, the rainfall interception, one part of the hydrological cycle, which returns water vapour to the atmosphere, contributing for the formation of new rains, was significantly changed by forest management, producing a decrease in the water retained by the forest canopy.

Soil water storage of Central Amazonian soil profiles in upland forest plots subjected to selective logging (in average, 8 trees or 34, 3 m³ of timber per hectare were removed) was measured in four layers, down to a depth of 70 cm. The study lasted 27-months and was divided in two phases: measurements were carried out nearly every week during the first 15 months; in the following year, five intensive periods of measurements were performed. Five damage levels were compared: (a) control (undisturbed forest plot); (b) centre of the clearing/gap; (c) edge of the gap; (d) edge of the remaining forest; and (e) remaining forest. The lowest values for water storage were found in the control (296 ± 19.1 mm), while the highest were observed (333 ± 25.8 mm) in the centre of the gap, during the dry period. In the older gaps (7.5-8.5 year old), soil water storage was similar to the remaining and the control forest, indicating a recovery of hydric soil properties to nearly the levels prior to selective logging.

Variáveis físicas do solo foram investigadas em parcelas de floresta de terra firme submetidas à extração seletiva de madeira na Amazônia central. Foram obtidas curvas de retenção de água no solo, juntamente com medidas de água disponível no solo às plantas, densidade do solo e porosidade total. Medidas de temperatura do solo foram realizadas por mais de 13 meses, considerando seis tratamentos: controle, centro da clareira, borda da clareira, borda da floresta remanescente, floresta remanescente e trilha do trator. Medidas de condutividade hidráulica de solo saturado foram feitas na floresta e em clareiras, sem distinguir os tratamentos. O solo revelou baixa capacidade de armazenar água disponível: apenas 11 a 18% da água pode estar disponível às plantas, num perfil de 1 m de profundidade. A temperatura das camadas superiores do solo foi influenciada pela extração seletiva de madeira: nas clareiras abertas, a luz chega com mais intensidade no solo, proporcionando temperaturas mais elevadas no centro e nas bordas das clareiras do que no controle e na floresta remanescente. Soil physical variables were investigated in forest plots submitted to selective logging in Central Amazonia. After logging, soil samples were collected to obtain soil water retention curves and measure: available soil water to the plants, soil density, and total porosity. Temperature measurements were carried out for 13 months, considering six treatments: control, center of the gaps, edge of the gaps, edge of the remaining forest, remaining forest and tractor tracks. Hydraulic conductivity measurements on saturated soil were conducted both on the control forest as well as on the logged plots, with no treatment distinction. The soil showed a low available water storage capacity: only 11 to 18% can be available to the plants, up to 1 meter depth. The temperature of the soil upper layers was influenced by logging, i. e., through the opening of the gaps, light reaches the soil more intensely in the center and edge of gaps, increasing temperatures in relation to the control and the remaining forest.

O regime hidrológico de nível de água baixo e alto torna as várzeas suscetíveis a alterações ecológicas, tanto nos solos quanto nos lagos. No período de nível de água alto, as várzeas são “fertilizadas” pelo sedimento cm suspensão que é depositado, tomando essas áreas as mais férteis da Região Amazônica. O presente trabalho avalia as características de solos e de sedimentos de dois lagos de várzea (Passarinho e Gravetão, situados próximo a Manaus) no que tange às propriedades físicas como a textura c curvas de retenção de água. Os resultados revelam que os solos e os sedimentos têm alta capacidade de reter a água, c consequentemente de água disponível, com valores máximos da ordem de 45 mm/10cm, considerando a água disponível entre os potenciais -10 e -1500 kPa. A fração silte da composição granulométrica foi, na maioria dos resultados, a mais expressiva, variou de 17 a 71%. The hydrologic regime, with high and low water levels make the low land very succeptible to ecological changes, in both soils and lakes. During high level periods, low land is “fertilized” by sediment deposition, making these areas the most fertile areas of the Amazonian region. This work is an evalution of soil and sediment characteristics of two low land lakes: Passarinho and Gravetão. They are situated near Manaus, Brazil. Parameters studied were: texture, and water retention. The results show that soils and sediments have high water retention properties, with maximum values around 45 mm/10cm, considering the available water between -10 and -1500 kPa. Silt is the main component in most samples, varying from 17 to 71%.

Sustainable use of the Amazon forest for timber production is conditioned by the effect of logging on the system's nutrient cycling. This paper reports the results of a soil moisture and soil water chemistry monitoring campaign before and immediately after a selective logging which removed 35 m(3) wood/ha. Soil moisture was measured using tensiometers, and soil water chemistry using suction samplers in five disturbance classes: tractor tracks, clearing centres, clearing edges, forest edges and untouched forest. The results show that the soil under the tractor tracks and clearings contained more moisture than under the untouched forest. The suction samplers extracted substantially more nitrate, ammonium, calcium, magnesium and potassium from the clearing centres, the tractor tracks and the clearing edges than from the forest sites. The results are explained in terms of altered microbial activity, changes in crown interception and uptake by roots.