Alterações no pulso de inundação: como reagem os igapós da Amazônia Central?

Igapós are floodplain forests inundated by acidic and nutrient-poor waters and occur along the black-water rivers, such as the Negro River and its tributaries, the Uatumã River and others in the Amazon Basin, covering more than 140,000 km2. Under natural conditions, the flood-pulse is monomodal and predictable, which drives the specialization and dependence of the flora to semiaquatic conditions. This work sought to understand how the igapós of two sub-basins in Central Amazonia perform under 1) normal conditions; 2) under the influence of extreme hydroclimatic events which increased dramatically during the last three decades (Jaú River, Negro River tributary); and 3) under flood-pulse disturbances (Uatumã River, Amazon River tributary) where the Balbina hydroelectric power plant was installed in the 1980s. For this, the igapó forests downstream the Uatumã River were classified and mapped to identify areas with massive tree mortality and where mortality is still occurring (first chapter). The mapping was done using 56 synthetic aperture radar images (ALOS/PALSAR) acquired at different flood levels between 2006 and 2011. The results showed that the application of object-based image analysis (OBIA) methods and the random forests supervised classification algorithm generated an overall accuracy of 87.2%. The mortality of 12% of the igapó forest was observed after the first 43 km downstream, along a stretch of 80 km. Based on the images and hydrological data, we detected 29% of the living igapó forests might be currently suffering mortality. Low topographies in the floodplains characterized by macrohabitats dominated by the tree species Eschweilera tenuifolia (O. Berg) Miers (Lecythidaceae) were the most impacted. To further study the ecology of this species, chapters 2 and 3 compare the macrohabitats in the two study areas to understand how and when flood pulse disturbances affected the growth and mortality of populations of this species, highly adapted to prolonged flooding conditions with flood durations of up to 10 months per year on average. Therefore, we collected discs of 30 dead individual trees and cylindrical cores (two per tree) from 62 living individuals in the Uatumã River igapós. In forests adjacent to the Jaú River, with natural tree mortality, we collected 21 discs from dead individuals and 31 cores from living trees. The second chapter discusses how the relationship between tree growth and climatic factors changed with the intensification of the hydrological cycle in natural environments (Jaú National Park - JNP) and the disturbed system (Uatumã Sustainable Development Reserve - USDR). For that, tree-ring chronologies were constructed at each study site, which presented robust statistics for the periods 1927-1999 (JNP) and 1920-2006 (USDR). The chronologies were related to regional parameters of hydrology (monthly water level) and climate (monthly precipitation) and with sea surface temperature anomalies (SST) of the Equatorial Pacific and Tropical Atlantic. The results suggest strong changes in the responses of Eschweilera tenuifolia trees to the intensification of the hydrological cycle, characterized by the increase in the frequency and magnitude of severe floods in the natural system (JNP) and by the increase of the minimum water level during the operational period of the Balbina dam (USDR). In the JNP, the trees indicate an increasing strength in the responses to the SST anomalies of both oceans, which reflects the described mechanisms that results in the intensification of the hydrological cycle, caused by the warming of the Tropical Atlantic and the simultaneous cooling of the Equatorial Pacific resulting in an intensification of Walker's circulation, strong cloud convection and increased precipitation in the northern and central sections of the Amazon Basin. In the USDR, the impacts of changes in the hydrological regime induced by the Balbina dam resulted in opposite responses of tree growth compared to the pre-dam period. The third chapter shows that the mean diameter increment (MDI) and mean age for trees in the JNP are 2.04 ± 0.39 mm and 201 ± 103 years, respectively, while trees at the USDR has MDI of 2.28 ± 0.69 mm and a mean age of 213 ± 103 years. The cumulative growth trajectory is similar between both areas for a 500-year period of growth modeling and the MDI analysis by periods indicates that overall the tree growth did not differ between both sites in the period before the construction of the Balbina hydroelectric power plant. In the same way, tree growth at JNP did show any significant difference between the periods before and after the intensification. Opposingly, the alteration of the flood pulse, caused by the operation of the dam, resulted in the MDI differentiation between the two periods at the USDR. The trees at USDR died about ten years after the beginning of the dam construction, whereas those from the JNP did not show a clear pattern throughout the evaluated periods. The living trees of USDR showed an increase in growth between 1982 and 2000 and an abrupt and strong growth decline after the year 2000, continuing until present day induced by the permanent flooding conditions leading to growth suppression and mortality. The change in the flood-pulse, more than 30 years after the disturbance, continues to cause growth anomalies and mortality in Eschweilera tenuifolia, which is highly sensitive to changes in flood amplitude and duration. In summary, the findings indicate the excessive mortality of trees is still occurring in the floodplains of the Uatumã River basin affecting especially macrohabitats dominated by this species, causing losses of ecosystem services and regional extinction of an extraordinary tree species. It is necessary that laws for the installation and norms for the operation of hydroelectric power plants in the Amazon should be carefully reviewed based on studies done in wetland areas downstream of dams.Os igapós de águas pretas são cobertos por florestas alagadas por águas ácidas e pobres em nutrientes, que ocorrem às margens de grandes rios como o Rio Negro, Rio Uatumã e outros da Bacia Amazônica, perfazendo mais de 140,000 km2. Naturalmente, esses ambientes possuem uma fase de águas altas (fase aquática) e uma fase de águas baixas (fase terrestre), caracterizando um pulso de inundação monomodal e previsível, o que permitiu a especialização e dependência da flora a condições semiaquáticas. Este trabalho buscou compreender como os igapós de duas sub-bacias na Amazônia Central se comportam em condições normais; sob influência de eventos hidro climáticos extremos que aumentaram drasticamente nas últimas três décadas (Rio Jaú, afluente do Rio Negro) e em condições severas de alteração no pulso de inundação (Rio Uatumã, afluente do Rio Amazonas) induzidas pela hidrelétrica de Balbina instalada nos anos 80. Para tal, a jusante do Rio Uatumã, no capítulo 1 mapeamos e classificamos os igapós para identificar áreas onde houve a mortalidade massiva de árvores e onde a mortalidade ainda está ocorrendo. O mapeamento foi feito com 56 imagens de radar de abertura sintética (ALOS/PALSAR) adquiridas em diferentes níveis de inundação entre 2006 e 2011. A classificação pelo algoritmo supervisionado (Random Forests) apresentou acurácia geral de 87,2%. Foi observada a mortalidade de 12% da floresta de igapó após os primeiros 43 km a jusante, ao longo de um trecho de 80 km. Com base nas imagens e dados hidrológicos, detectamos que 29% dos remanescentes de igapó vivos podem estar atualmente sofrendo mortalidade. Os resultados indicaram que principalmente as topografias baixas caracterizadas por macro-habitats dominadas pela espécie arbórea Eschweilera tenuifolia (O. Berg) Miers (Lecythidaceae) foram os mais impactados. Para estudar em mais detalhe a ecologia desta espécie arbórea os capítulos 2 e 3, comparam os macro-habitats nas duas áreas de estudo, visando compreender como e quando os distúrbios no pulso de inundação afetaram as populações desta espécie, altamente adaptada às condições de inundações prolongadas de até 10 meses por ano em média. Nos igapós do Rio Uatumã, coletamos discos de 30 árvores mortas e bastões de madeira (duas amostras por árvore retirados com trado dendrocronológico) de 62 indivíduos vivos. Em florestas de igapó adjacentes ao Rio Jaú, coletamos 21 discos de indivíduos mortos e bastões de madeira de 31 indivíduos vivos. O segundo capítulo aborda as relações entre crescimento arbóreo e fatores climáticos em ambientes naturais (Parque Nacional do Jaú - PNJ) e perturbados (Reserva de Desenvolvimento Sustentável do Uatumã - RDSU). Para isso foram construídas cronologias de anéis de crescimento em cada sítio de estudo que apresentam estatísticas robustas para os períodos 1927-1999 (PNJ) e 1920-2006 (RDSU). As cronologias foram relacionadas com parâmetros regionais de hidrologia (nível mensal da água) e clima (precipitação mensal) e com anomalias de temperaturas superficiais do mar (TSM) do Pacífico Equatorial e Atlântico Tropical. Os resultados sugerem fortes mudanças nas respostas das árvores de Eschweilera tenuifolia à intensificação do ciclo hidrológico, caracterizado pelo aumento da frequência e magnitude de cheias severas no sistema natural (PNJ) e pelo aumento do nível mínimo da água durante o período da operação da barragem de Balbina (RDSU). No PNJ as árvores indicam um aumento nas respostas às anomalias de TSM dos dois oceanos (correlação positiva) em resposta da intensificação do ciclo hidrológico, causada pelo aquecimento do Atlântico Tropical e o simultâneo esfriamento do Pacífico Equatorial resultando na intensificação da circulação de Walker, forte convecção de nuvens e aumento de precipitação nas secções norte e central da Bacia Amazônica. Na RDSU, os impactos das mudanças do regime hidrológico induzidas pela barragem de Balbina resultaram em respostas do crescimento arbóreo opostas ao período pré-barragem. O terceiro capítulo aborda o crescimento arbóreo e a mortalidade da espécie nos dois sítios por meio de análises de séries temporais de incrementos diamétricos e datação com radiocarbono para detectar mudanças nos padrões de crescimento e mortalidade e suas causas. Os resultados mostram que o incremento diamétrico médio (IMD) e a idade média para árvores do PNJ foram 2,04 ± 0,39 mm e 201 ± 103 anos (DAP médio: 43,9 ± 21,7 cm) , respectivamente, enquanto para árvores da RDSU o IMD foi 2,28 ± 0,69 mm e a idade média 213 ± 103 anos (DAP médio: 45,9 ± 24,6 cm). A trajetória de crescimento acumulado entre os dois sítios de estudo foi similar, ao considerarmos um período de 500 anos de modelagem do crescimento. O IMD foi comparado entre os dois sítios de estudo e entre períodos antes e após (a partir de 1982) das mudanças do ciclo hidrológico induzidas por mudanças de clima (PNJ) e UHE (RDSU). O período anterior à construção da usina hidrelétrica (UHE) de Balbina indica que o crescimento das árvores não diferiu entre os dois sítios de estudo. Da mesma forma, o IMD das árvores no PNJ não apresentou diferença entre os períodos antes e depois de 1982. Em contraste, a manipulação do pulso de inundação ocasionada pela operação da UHE resultou na diferenciação do IMD entre as duas áreas e entre os períodos no Rio Uatumã. As árvores do Rio Uatumã morreram cerca de dez anos após o início da construção da barragem enquanto as árvores do Rio Jaú não apresentaram um padrão distinto de mortalidade ao longo da cronologia avaliada. As árvores vivas do Rio Uatumã apresentaram um aumento no incremento entre 1982 e 2000 e um abrupto e forte declínio de IMD após o ano 2000, que perdura até hoje, caracterizando um padrão de supressão de crescimento induzido pelas condições permanentes de inundação que possivelmente resultará em mortalidade. Com isso, concluímos que a alteração do pulso de inundação, causou e continua causando anomalias no crescimento e mortalidade de Eschweilera tenuifolia, mesmo em mais de 30 anos após a perturbação. A espécie é altamente sensível às mudanças na amplitude e duração da inundação que impactam os macro-habitats dominados por ela. A mortalidade massiva de árvores pode levar a perda destes macro-habitats, serviços ecossistêmicos e até a extinção regional da espécie. É necessário que as leis para a instalação e funcionamento de UHEs na Amazônia sejam criteriosamente revisadas com base em estudos feitos em áreas alagáveis a jusante das barragens

Fires in Amazonian Blackwater Floodplain Forests: Causes, Human Dimension, and Implications for Conservation

The Amazon basin is being increasingly affected by anthropogenic fires, however, most studies focus on the impact of fires on terrestrial upland forests and do not consider the vast, annually inundated floodplains along the large rivers. Among these, the nutrient-poor, blackwater floodplain forests (igapós) have been shown to be particularly susceptible to fires. In this study we analyzed a 35-year time series (1982/1983–2016/2017) of Landsat Thematic Mapper from the Jaú National Park (Central Amazonia) and its surroundings. Our overall objective was to identify and delineate fire scars in the igapó floodplains and relate the resulting time series of annual burned area to the presence of human populations and interannual variability of regional hydroclimatic factors. We estimated hydroclimatic parameters for the study region using ground-based instrumental data (maximum monthly temperature–T$_{max}$, precipitation–P, maximum cumulative water deficit–MCWD, baseflow index–BFI, minimum water level–WL$_{min90}$ of the major rivers) and large-scale climate anomalies (Oceanic Niño Index–ONI), considering the potential dry season of the non-flooded period of the igapó floodplains from September to February. Using a wetland mask, we identified 518,135 ha of igapó floodplains in the study region, out of which 17,524 ha (3.4%) burned within the study period, distributed across 254 fire scars. About 79% of the fires occurred close to human settlements (<10 km distance), suggesting that human activities are the main source of ignition. Over 92.4% of the burned area is associated with El Niño events. Non-linear regression models indicate highly significant relationships (p < 0.001) with hydroclimatic parameters, positive with T$_{max}$ (R$^{2}$adj. = 0.83) and the ONI (R$^{2}$adj. = 0.74) and negative with P (R$^{2}$adj. = 0.88), MCWD (R$^{2}$adj. = 0.90), WL$_{min90}$ (R$^{2}$adj. = 0.61) and BFI (R$^{2}$adj. = 0.80). Hydroclimatic conditions were of outstanding magnitude in particular during the El Niño event in 2015/2016, which was responsible for 42.8% of the total burned floodplain area. We discuss these results under a historical background of El Niño occurrences and a political, demographic, and socioeconomic panorama of the study region considering the past 400 years, suggesting that disturbance of igapós by fires is not a recent phenomenon. Concluding remarks focus on current demands to increase the conservation to prevent and mitigate the impacts of fire in this vulnerable ecosystem

Association between the occurence of iron-deficiency anemia with socioeconomic variables and school performance

Study design: Cross-sectional observational. Objective: Evaluate the association between the occurence of iron-deficiency anemia with socioeconomic variables and school performance. Method: They were included in the study 124 children aged between six and eight years old, municipal elementary school students, which were divided in two groups according to the presence (n=32) or absence of anemia (n=92). Hemoglobin and serum iron levels were determined by colorimetric method, red blood cells count was performed using Neubauer chamber, hematocrit was evaluated using microhematocrit centrifuge, and mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration hematimetric indexes were calculated. The school performance of children was provided by participating schools and socioeconomic variables were obtained by filling out the clinic file and the socioeconomic questionnaire of Brazilian Association of Research Companies by parents or guardians. Results: The prevalence of iron-deficiency anemia in school children was 25.8%, which is considered to be moderate. The proportion of better school grades was higher in children without anemia and in those belonging to the upper socioeconomic levels. However, it was not observed statistically differences between groups regarding school performance and socioeconomic variables. Conclusion: A moderate prevalence of iron-deficiency anemia was found in children aged between six and eight years old, however, it was not observed a significant association between irondeficiency anemia with socioeconomic variables and school performance.Modelo do estudo: Observacional transversal. Objetivo: Avaliar a associação entre a presença de anemia ferropriva com variáveis socioeconômicas e rendimento escolar. Método: Foram incluídas no estudo 124 crianças com idade entre seis e oito anos, estudantes do ensino fundamental de escolas municipais, as quais foram divididas em dois grupos de acordo com a presença (n=32) ou ausência de anemia (n=92). Os níveis de hemoglobina e ferro sérico foram determinados por método colorimétrico, a contagem de hemácias foi realizada utilizando a câmara de Neubauer, o hematócrito foi avaliado utilizando centrífuga de microhematócrito, e foram calculados os índices hematimétricos volume corpuscular médio, hemoglobina corpuscular média e concentração de hemoglobina corpuscular média. O desempenho escolar das crianças foi fornecido pelas escolas participantes e as variáveis socioeconômicas foram obtidas através de preenchimento de ficha clínica e do questionário socioeconômico da Associação Brasileira das Empresas de Pesquisa pelos pais ou responsáveis. Resultados: A prevalência de anemia ferropriva nos escolares foi de 25,8% que é considerada pelos parâmetros da OMS uma prevalência moderada. Foi observada uma maior proporção de crianças sem anemia que apresentaram melhores conceitos escolares e que pertencem aos níveis socioeconômicos mais altos do que de crianças com anemia. Contudo, não foram observadas diferenças estatisticamente significativas entre os grupos com relação ao rendimento escolar e as variáveis socioeconômicas. Conclusão: Uma prevalência moderada de anemia ferropriva foi encontrada nas crianças com idade entre seis e oitos anos, entretanto, não foi observada uma associação significativa entre a anemia ferropriva com variáveis socioeconômicas e o rendimento escolar

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Incêndios rasteiros em florestas alagáveis e de terra firme na Amazônia central

A fire in November 2009 about 100 km south of Manaus penetrated seasonally flooded forest of low fertility (igapó) and neighboring upland forest, providing a natural experiment for comparing fire damage between these two widespread Amazonian forest types. In ten plots of 250 m x 20 m, basal area (> 10 cm DBH) and stem density were measured in each forest type, 3- 4 years after the fire. Ten unburned plots per forest type were used as proxies for pre-burn forest structure. As indicators of fine fuel flammability, five sensors were installed 50 cm above the litter layer in each of the unburned forest types in the 2013 dry season, providing a comparison of mid-day extremes of relative humidity and temperature. Both forest types had significantly lower stem density after burning, when compared to unburned forest of the same type. The average stem loss of 59% in the flooded forests was significantly greater (p=0.001 ANOVA) than the 18% of stem loss in terra firme forest. Average basal area loss was 49% in the flooded forest, also higher (p=0.034, Mann-Whitney U test) than in terra firme forest (23 %). Mid-day extremes of relative humidity were lower (p=0.009) and extremes of temperature were higher (p=0.008, Mann-Whitney U test) in the understory of seasonally flooded forest. The study allowed us to conclude that the infertile floodplain forests are more flammable. This difference in microclimate -- together with higher fuel loads and greater susceptibility of fine roots to fire damage in a superficial the root mat shown in a previous study – leads to greater damage when floodplain forests (igapó) are penetrated by ground fires.Um incêndio ocorrido em novembro de 2009 a cerca de 100 km ao sul de Manaus penetrou florestas de baixa fertilidade inundadas sazonalmente (igapós) e florestas de terra firme próximas, proporcionando um experimento natural para a comparação do dano causado pelo fogo entre estes dois tipos de ecossistemas florestais da amazônica. Em dez parcelas de 250 m x 20 m, a área basal (DAP> 10 cm) e a densidade de indivíduos foram mensurados, em cada tipologia florestal, 3-4 anos após o incêndio. Dez parcelas não queimadas por tipo de floresta foram utilizadas como testemunho para representar a estrutura das mesmas antes do fogo. Como indicadores de inflamabilidade do combustível fino, cinco sensores foram instalados 50 centímetros acima da serapilheira em cada um dos tipos florestais não queimados, na estação seca de 2013, fornecendo uma comparação dos extremos de temperatura e umidade relativa ao meio- dia. Ambas as tipologias florestais tinham significativamente menor número de indivíduos (densidade) após a queimada, quando comparadas à floresta não queimada do mesmo tipo. A perda de densidade média foi de 59 % nas florestas inundadas, o que foi significativamente maior (p = 0,001 ANOVA) do que os 18% perdidos em floresta de terra firme. A perda média de área basal foi de 49% na floresta inundada, também maior (p = 0,034, teste U de Mann -Whitney) do que em terra firme (23%). Os extremos de umidade relativa do ar por volta do meio-dia foram inferiores (p = 0,009) e os extremos de temperatura foram maiores (p = 0,008, teste U de Mann - Whitney) no sub-bosque da floresta inundada. O estudo permitiu concluir que as florestas inundáveis de baixa fertilidade são mais inflamáveis. Esta diferença de microclima, juntamente com cargas de combustível mais elevadas e maior susceptibilidade de raízes finas a danos por fogo em uma camada superficial do tapete de raízes leva a um maior dano quando florestas alagáveis de igapó são atingidas por incêndios rasteiros

Fire damage in seasonally flooded and upland forests of the Central Amazon

Neighboring upland and nutrient-poor seasonally flooded Amazon forests were penetrated by a fire in 2009, providing a natural comparative experiment of fire damage for these widespread forest types. In upland, only 16 ± 10% (±2 SEM) of stems and 21 ± 8% of basal area were lost to fire, while seasonally flooded forest lost 59 ± 13% of stems and 57 ± 13% of basal area. Drier understory contributes to greater flammability. Much of the area occupied by seasonally flooded woody vegetation (>11.5 percent of the Amazon region) is vulnerable to fire due to high flammability and slow recovery. © 2014 The Association for Tropical Biology and Conservation