Species composition and similarities among anuran assemblages of forest sites in southeastern Brazil

As florestas neotropicais apresentam altas riquezas de espécies de anuros, mas algumas formações florestais brasileiras, como o cerradão, as florestas semidecíduas e as restingas, permanecem pouco conhecidas. A composição de espécies de anuros de quatro áreas florestais pertencentes a diferentes biomas do sudeste do Brasil foi determinada com base em duas técnicas complementares (procura visual e investigação nos sítios reprodutivos), aplicadas de forma simultânea. Registramos um total de 60 espécies de anuros, incluídas em oito famílias. A riqueza de espécies e o nível de endemismo foram maiores na área coberta por floresta pluvial atlântica. As áreas localizadas no domínio do Cerrado foram mais similares entre si do que as áreas localizadas no domínio da Mata Atlântica. Os índices de similaridade mostraram-se negativamente relacionados com a distância geográfica entre as áreas, explicando parte das similaridades observadas. Os fatores que influenciam os padrões de ocorrência são discutidos. Uma das espécies (caso sua identidade seja confirmada) é considerada como Deficiente em Dados pela IUCN (The World Conservation Union), mas não está incluída na lista da fauna brasileira ameaçada de extinção. A presença de certas espécies com requisitos especiais de hábitat e microclima (bioindicadores) sugerem que os ecossistemas estão bem-preservados.Neotropical forests show high anuran species richness, but some Brazilian forest formations, like cerradão, semideciduous forests and restingas, remain poorly known. The composition of anuran species were determined for four forest sites belonging to different biomes in southeastern Brazil, based on two complementary techniques (visual encounter survey and survey on breeding sites), both applied simultaneously. A total of 60 anuran species belonging to eight families was recorded. Species richness and levels of endemism were higher in the Atlantic rainforest site. Sites located in the Cerrado domain were more alike than those located in the Atlantic Forest Domain. Similarity in anuran species composition was negatively correlated to the geographical distance among sites, which explains part of similarities in species composition. Factors affecting these occurrence patterns are discussed. One species (if its identity is confirmed) is considered Data Deficient by IUCN (The World Conservation Union), though it is not included in the Brazilian list of threatened amphibians. The presence of certain species with special habitats and microclimate requirements (bioindicators) suggests well-preserved ecosystems

The importance of plants for methane emission at the ecosystem scale

Methane (CH4), one of the key long-lived atmospheric greenhouse gases, is primarily produced from organic matter. Accordingly, net primary production of organic matter sets the boundaries for CH4 emissions. Plants, being dominant primary producers, are thereby indirectly sustaining most global CH4 emissions, albeit with delays in time and with spatial offsets between plant primary production and subsequent CH4 emission. In addition, plant communities can enhance or hamper ecosystem production, oxidation, and transport of CH4 in multiple ways, e.g., by shaping carbon, nutrient, and redox gradients, and by representing a physical link be-tween zones with extensive CH4 production in anoxic sediments or soils and the atmosphere. This review focuses on how plants and other primary producers influence CH4 emissions with the consequences at ecosystem scales. We outline mechanisms of interactions and discuss flux regulation, quantification, and knowledge gaps across multiple ecosystem examples. Some recently proposed plant-related ecosystem CH4 fluxes are difficult to reconcile with the global atmospheric CH4 budget and the enigmas related to these fluxes are highlighted. Overall, ecosystem CH4 emissions are strongly linked to primary producer communities, directly or indirectly, and properly quantifying magnitudes and regulation of these links are key to predicting future CH4 emissions in a rapidly changing world.Funding Agencies|European Research Council (ERC) [725546]; Swedish Research Councils VR [2016-04829]; Formas [2018- 01794, 2018-00570]; ERC H2020 [851181]; Helmholtz Impulse and Networking Fund; UK NERC [NE/J010928/1, NE/N015606/1]; AXA Research Fund [426]; Royal Society; Royal Society Dorothy Hodgkin Research Fellowship [DH160111]; Swedish Research Council Formas [2021-02429]</p

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

The Xingu and Tapajós rivers in the eastern Amazon are the largest clearwater systems of the Amazon basin. Both rivers have “fluvial rias” (i.e., lake-like channels) in their downstream reaches as they are naturally impounded by the Amazon mainstem. Fluvial rias are widespread in the Amazon landscape and most of the sedimentary load from the major clearwater and blackwater rivers is deposited in these channels. So far, little is known about the role of Amazon rias as a trap and reactor for organic sediments. In this study, we used organic and inorganic geochemistry, magnetic susceptibility, diatom, and pollen analyses in sediments (suspended, riverbed, and downcore) of the Xingu and Tapajós rias to investigate the effects of hydrologic variations on the carbon budget in these clearwater rivers over the Holocene. Ages of sediment deposition (~100 to 5,500 years) were constrained by optically stimulated luminescence and radiocarbon. Major elements geochemistry and concentration of total organic carbon (TOC) indicate that seasonal hydrologic variations exert a strong influence on riverine productivity and on the input and preservation of organic matter in sediments. Stable carbon isotope data (δ13C from −31.04 to −27.49‰) and pollen analysis indicate that most of the carbon buried in rias is derived from forests. In the Xingu River, diatom analysis in bottom sediments revealed 65 infrageneric taxa that are mostly well-adapted to slack oligotrophic and acidic waters. TOC values in sediment cores are similar to values measured in riverbed sediments and indicate suitable conditions for organic matter preservation in sediments of the Xingu and Tapajós rias at least since the mid-Holocene, with carbon burial rates varying from about 84 g m−2 yr−1 to 169 g m−2 yr−1. However, redox-sensitive elements in sediment core indicate alternation between anoxic/dysoxic and oxic conditions in the water-sediment interface that may be linked to abrupt changes in precipitation. The variation between anoxic/dysoxic and oxic conditions in the water-sediment interface controls organic matter mineralization and methanogenesis. Thus, such changes promoted by hydrological variations significantly affect the capacity of Amazon rias to act either as sources or sinks of carbon

Performance of Landsat-8 and Sentinel-2 Surface Reflectance Products for River Remote Sensing Retrievals of Chlorophyll-A and Turbidity

Rivers and other freshwater systems play a crucial role in ecosystems, industry, transportation and agriculture. Despite the more than 40 years of inland water observations made possible by optical remote sensing, a standardized reflectance product for inland waters is yet forthcoming. The aim of this work is to compare the standard USGS land surface reflectance product to two Landsat-8 and Sentinel-2 aquatic remote sensing reflectance products over the Amazon, Columbia and Mississippi rivers. Landsat-8 reflectance products from all three routines are then evaluated for their comparative performance in retrieving chlorophyll-a and turbidity in reference to shipborne, underway in situ validation measurements. The land surface product shows the best agreement (4 percent Mean Absolute Percent Difference) with field measurements of radiometry collected on the Amazon River and generates 36 percent higher reflectance values in the visible bands compared to aquatic methods (ACOLITE (Atmospheric Correction for OLI (Operational Land Imager) 'lite') and SeaDAS (Sea-viewing Wide Field-of-View Sensor (SeaWiFS) Data Analysis System)) with larger differences between land and aquatic products observed in Sentinel-2 (0.01 per steraradian) compared to Landsat-8 (0.001 per steraradian). Choice of atmospheric correction routine can bias Landsat-8 retrievals of chlorophyll-a and turbidity by as much as 59 percent and 35 percent respectively. Using a more restrictive time window for matching in situ and satellite imagery can reduce differences by 531 percent depending on correction technique. This work highlights the challenges of satellite retrievals over rivers and underscores the need for future optical and biogeochemical research aimed at improving our understanding of the absorbing and scattering properties of river water and their relationships to remote sensing reflectance

Land use land and cover changes in the middle Araguaia river basin, central Brazil

A região do médio rio Araguaia está localizada em uma área de transição entre a Floresta Tropical e o Cerrado, região esta que vem sofrendo um intenso processo de desmatamento nas últimas décadas. Contudo, a quantificação e os impactos destas alterações são ainda pouco conhecidos. Portanto, este estudo teve como objetivo avaliar a dinâmica temporal das alterações na estrutura da paisagem na bacia do médio Araguaia, entre 1975 e 2007, e os fatores relacionados a estas alterações. O capítulo 1 apresenta uma contextualização científica desta pesquisa. Os outros 4 capítulos apresentam manuscritos que serão submetidos a publicação. O capítulo 2 analisa as alterações no uso e cobertura da terra na região do Parque Estadual do Cantão (Tocantins) para um período de 19 anos, entre 1981 e 2000. Nossos resultados mostraram que a redução da vegetação nativa e conseqüente aumento de áreas agropastoris está associada ao aumento da fragmentação. Observamos também uma baixa conversão da vegetação nativa no interior do parque. No entanto, estes baixos valores podem estar associados à localização da reserva, dentro da planície de inundação do rio Araguaia. O capítulo 3 mostra os resultados do mapeamento do uso e cobertura do solo para o médio Araguaia nos anos de 1975, 1985, 1996 e 2007. Para tal, foi utilizado o método de classificação híbrida. O mapeamento apresentou uma acurácia geral de 85%. A extensão da área perdida das três classes de cobertura nativa (floresta, cerrado aberto e cerrado stricto), ao longo destes 32 anos analisados, totaliza uma redução de 26% destas coberturas. Os resultados dos efeitos destas mudanças na estrutura e configuração da paisagem são apresentados no capítulo 4. A análise da composição mostrou que, áreas de floresta e cerrado stricto foram as mais afetadas pelas conversões. Em relação à configuração da paisagem, foi verificada uma considerável redução no tamanho do maior fragmento, principalmente de floresta, que foi acompanhado do aumento no número de pequenos fragmentos. Por sua vez, esta apresenta uma relação com o aumento da densidade de borda, diminuição das áreas centrais médias e aumento da distância entre os fragmentos, resultado que mostra um elevado índice de fragmentação da vegetação nativa remanescente. Por fim, no capítulo 5, apresentamos os resultados sobre os remanescentes de cobertura nativa em 2007. Dos 166 mil km² da área estudada, 86.808 km² eram de vegetação primária em 2007. Com isso foi realizada uma análise de regressão logística para identificar a influência da distância de estradas, distância de cidades, declividade do terreno, situação fundiária, fertilidade do solo e ocorrência de alagamento no processo de desmatamento. Valores significativos (p<0,05) mostram que o distanciamento de estradas e cidades, o aumento da declividade, a presença de unidades de conservação de proteção integral, terras indígenas, áreas alagáveis e áreas com baixa fertilidade apresentam influência positiva para a presença e manutenção de áreas primárias. A análise destes processos é muito importante para um melhor entendimento da dinâmica regional de uso do solo, além de fornecer informações de apoio para um planejamento regional mais eficiente e sustentável.The central region of the Araguaia river basin encompasses a transition area between the Tropical Rain Forest and the Cerrado in Brazil. Despite of the fact that during the last four decades, this area has undergone an intense deforestation process, the quantification and impact of these changes are still unknown. Thus this study aimed to evaluate the dynamics of changes in landscape structure in the middle Araguaia river basin; and the driving factors of such changes.Chapter 1 of this thesis introduces the scientific contextualization of this research. The other 4 chapters present manuscripts to be submitted for publication. Chapter 2 analyzes the land use and land cover changes in the Cantão State Park region, Tocantins, for a period of 19 years, from 1981 to 2000. Our findings showed that the reduction of native vegetation and consequent increase of agricultural and pasture areas were related to the increase of fragmentation. We observed low conversion of native vegetation inside of the park area. However, these low rates of native vegetation losses may be associated with the geographical location of the reserve within the Araguaias floodplain.Chapter 3 present the results of the land use and land cover mapping of the middle Araguaia region for 1975, 1985, 1996 and 2007. To derive these maps, a hybrid classification method was implemented. The mapping showed an overall accuracy of 85%. The extent of native cover (forest, open cerrado and cerrado stricto) changes over the 32 years totalized a reduction of 26% of these land covers. The results of the effects of these changes in landscape structure and configuration were evaluated in Chapter 4. Our analysis of landscape composition showed that areas of forest and cerrado stricto were the most affected by conversions. Regarding the landscape configuration, there was a considerable reduction in the largest patch index, mainly of forest, which was followed by an increase in the number of small patches, which in turn was related to the increase of edge density, decrease of core areas and increase in the mean patch distance. These results indicate a high degree of fragmentation of remaining native vegetation.Finally, Chapter 5 analyzes the native vegetation cover remnants in 2007. Of the 166,000 km² of the study area, 86,808 km² were remnants of primary vegetation. Then, we performed a logistic regression analysis to identify the influence of distance from roads, distance from cities, slope, land tenure, fertility and the occurrence of flooding in the deforestation process. Significant values (p <0.05) for all variables were obtained, showing that the distance from roads and cities, slope increase, presence of conservation units, indigenous lands, wetlands and areas with low fertility have a positive influence for the presence and maintenance of primary vegetation. The analysis of these processes is very important for better understanding the regional dynamics of land use, and provide supporting information for a more efficient and sustainable regional planning

Land use land and cover changes in the middle Araguaia river basin, central Brazil

A região do médio rio Araguaia está localizada em uma área de transição entre a Floresta Tropical e o Cerrado, região esta que vem sofrendo um intenso processo de desmatamento nas últimas décadas. Contudo, a quantificação e os impactos destas alterações são ainda pouco conhecidos. Portanto, este estudo teve como objetivo avaliar a dinâmica temporal das alterações na estrutura da paisagem na bacia do médio Araguaia, entre 1975 e 2007, e os fatores relacionados a estas alterações. O capítulo 1 apresenta uma contextualização científica desta pesquisa. Os outros 4 capítulos apresentam manuscritos que serão submetidos a publicação. O capítulo 2 analisa as alterações no uso e cobertura da terra na região do Parque Estadual do Cantão (Tocantins) para um período de 19 anos, entre 1981 e 2000. Nossos resultados mostraram que a redução da vegetação nativa e consequente aumento de áreas agropastoris está associada ao aumento da fragmentação. Observamos também uma baixa conversão da vegetação nativa no interior do parque. No entanto, estes baixos valores podem estar associados à localização da reserva, dentro da planície de inundação do rio Araguaia. O capítulo 3 mostra os resultados do mapeamento do uso e cobertura do solo para o médio Araguaia nos anos de 1975, 1985, 1996 e 2007. Para tal, foi utilizado o método de classificação híbrida. O mapeamento apresentou uma acurácia geral de 85%. A extensão da área perdida das três classes de cobertura nativa (floresta, cerrado aberto e cerrado stricto), ao longo destes 32 anos analisados, totaliza uma redução de 26% destas coberturas. Os resultados dos efeitos destas mudanças na estrutura e configuração da paisagem são apresentados no capítulo 4. A análise da composição mostrou que, áreas de floresta e cerrado stricto foram as mais afetadas pelas conversões. Em relação à configuração da paisagem, foi verificada uma considerável redução no tamanho do maior fragmento, principalmente de floresta, que foi acompanhado do aumento no número de pequenos fragmentos. Por sua vez, esta apresenta uma relação com o aumento da densidade de borda, diminuição das áreas centrais médias e aumento da distância entre os fragmentos, resultado que mostra um elevado índice de fragmentação da vegetação nativa remanescente. Por fim, no capítulo 5, apresentamos os resultados sobre os remanescentes de cobertura nativa em 2007. Dos 166 mil km² da área estudada, 86.808 km² eram de vegetação primária em 2007. Com isso foi realizada uma análise de regressão logística para identificar a influência da distância de estradas, distância de cidades, declividade do terreno, situação fundiária, fertilidade do solo e ocorrência de alagamento no processo de desmatamento. Valores significativos (p<0,05) mostram que o distanciamento de estradas e cidades, o aumento da declividade, a presença de unidades de conservação de proteção integral, terras indígenas, áreas alagáveis e áreas com baixa fertilidade apresentam influência positiva para a presença e manutenção de áreas primárias. A análise destes processos é muito importante para um melhor entendimento da dinâmica regional de uso do solo, além de fornecer informações de apoio para um planejamento regional mais eficiente e sustentável.The central region of the Araguaia river basin encompasses a transition area between the Tropical Rain Forest and the Cerrado in Brazil. Despite of the fact that during the last four decades, this area has undergone an intense deforestation process, the quantification and impact of these changes are still unknown. Thus this study aimed to evaluate the dynamics of changes in landscape structure in the middle Araguaia river basin; and the driving factors of such changes. Chapter 1 of this thesis introduces the scientific contextualization of this research. The other 4 chapters present manuscripts to be submitted for publication. Chapter 2 analyzes the land use and land cover changes in the Cantão State Park region, Tocantins, for a period of 19 years, from 1981 to 2000. Our findings showed that the reduction of native vegetation and consequent increase of agricultural and pasture areas were related to the increase of fragmentation. We observed low conversion of native vegetation inside of the park area. However, these low rates of native vegetation losses may be associated with the geographical location of the reserve within the Araguaias floodplain. Chapter 3 present the results of the land use and land cover mapping of the middle Araguaia region for 1975, 1985, 1996 and 2007. To derive these maps, a hybrid classification method was implemented. The mapping showed an overall accuracy of 85%. The extent of native cover (forest, open cerrado and cerrado stricto) changes over the 32 years totalized a reduction of 26% of these land covers. The results of the effects of these changes in landscape structure and configuration were evaluated in Chapter 4. Our analysis of landscape composition showed that areas of forest and cerrado stricto were the most affected by conversions. Regarding the landscape configuration, there was a considerable reduction in the largest patch index, mainly of forest, which was followed by an increase in the number of small patches, which in turn was related to the increase of edge density, decrease of core areas and increase in the mean patch distance. These results indicate a high degree of fragmentation of remaining native vegetation. Finally, Chapter 5 analyzes the native vegetation cover remnants in 2007. Of the 166,000 km² of the study area, 86,808 km² were remnants of primary vegetation. Then, we performed a logistic regression analysis to identify the influence of distance from roads, distance from cities, slope, land tenure, fertility and the occurrence of flooding in the deforestation process. Significant values (p <0.05) for all variables were obtained, showing that the distance from roads and cities, slope increase, presence of conservation units, indigenous lands, wetlands and areas with low fertility have a positive influence for the presence and maintenance of primary vegetation. The analysis of these processes is very important for better understanding the regional dynamics of land use, and provide supporting information for a more efficient and sustainable regional planning

Water influence on CH4 and CO2 generation from tar sandstones: Insights from incubation experiments in the Piramboia Formation, Parana Basin

Processes controlling the biogenic production of CH4 and CO2 are relevant not only to environmental issues related to greenhouse gases emissions, but also in the energy scenario, since the biogenic generation of CH4 can be associated with the formation of natural gas reserves over time. This work aimed to evaluate the influence of water and calcium sulfate in the production of CH4 and CO2 from petroleum biodegradation in tar sandstones. Water saturation and sulfate concentration are taken to be important factors of influence in the oil biodegradation process. Long-term incubation experiments (up to 363 days) were carried out with samples of sandstone impregnated with high-viscosity hydrocarbons. The rocks used in this study were collected from outcrops of the Piramboia Formation, a known heavy-oil reservoir of the Parana Basin, Brazil. The net accumulation of both CH4 and CO2 was crescent during all the experiments performed, but with decreasing production rates through time. Average potential production rates obtained were 18 mL CH4/t.y (milliliter per ton of sandstone per year) and 54,000 mL CO2/t.y. The addition of water resulted in an average increase of 11% and 10% in the CH4 and CO2 cumulative production, respectively, in comparison with the dry incubation experiments. The water influence was stronger in the first 30 days of incubations when average production was around 70% higher in wet samples. Once the pH remained constant in the presence of calcium sulfate, the experiments indicate that calcium sulfate may function as buffer for pH, limiting acidification, which has a known negative influence on CH4 and CO2 production. Thus, the present work aims to alert for the potential of CO2 and CH4 production from tar sands in Brazil and for the importance of water as a positive influence on CH4 and CO2 generation from tar sandstones. This helps to evaluate the influence of environmental conditions on biogenic gas systems as well as on green-house gases emissions from geological sources, which are taken to be important sources of carbon to the atmosphere in a context of climate change.Funding Agencies|Project "Avaliacao da geracao de metano biogenico nas formacoes Ponta Grossa e Irati, Bacia do Parana" (CNPq) [454362/2014-5]; Programa de Formacao de Recursos Humanos em Geologia do Petroleo e Meio Ambiente [PFRH-241-Petrobras]; CNPqNational Council for Scientific and Technological Development (CNPq) [304727/2017-2]</p