Letteratura scientifica selezionata sul tema "Amazonian slope"

In northern South America, an extensive tropical lowland runs 5,000 km from the Atlantic coast to the foot of the Andes. The slope is gentle until about 500 m where the eastern Andes rise abruptly. The lowland supports Amazonia, which is the most extensive tract of tropical rainforest on the planet. Most of its boundaries are well defined, but the boundary between Amazonia and the forest of the eastern slopes of the Andes has not been clearly defined. To determine for avifauna whether Amazonia is restricted to the lowland of northern South America or whether it also extends up into the eastern slopes of the Andes, different types of data were used. The results indicate that Amazonia may be restricted to the lowland that extends from the Atlantic coast to the foot of the Andes, up to about 500 m. Consequently, the number of bird species strictly endemic to Amazonia would be 290. Comparison with the distribution of vegetation on the eastern slopes of the Andes also suggests that Amazonia as a biome may be restricted to the lowland that extends from the Atlantic coast to the foot of the Andes, up to about 500 m.

Four new species of Lispinus from the premontane forest of the eastern slope of the Peruvian Andes are described and records of all other Lispinus species from Peru are given. The new species are: L. blandus, L. minimus, L. speciosus, and L. peruanus. A key to the known 21 Peruvian species is provided, habitat information is summarized and geographical distribution of species is discussed. The following six types of zoogeographic distribution can be differentiated for the Peruvian Lispinus species: endemic, eastern Andean, lowland Amazonian, Circum-Amazonian, northern Southand Central-American, and Pan-Neotropical.

AbstractWe report the first record of the rare Koepcke’s spear-nosed bat Gardnerycteris koepckeae collected outside of Peru, based on morphological and cytochrome b data. The species was found at the National Natural Park Alto Fragua Indi-Wasi, Department of Caquetá, Colombia. This record extended the species distribution 1400 km north from the northernmost known locality in Huanhuachayo, Ayacucho, Peru. This finding suggests that G. koepckeae is distributed over middle elevations along the eastern slope of the Andean-Amazonia foothills in Peru and Colombia, similar to other Phyllostomid bats, such as Vampyressa melissa and Lonchophylla handleyi. We reviewed the threatened category of G. koepckeae, currently categorized as Data Deficient (DD), according to the International Union for Conservation of Nature (IUCN), but considered as Endangered (EN) in recent papers. Based on this new record, we suggest that the species should be included in future assessments as Near Threatened (NT) or Vulnerable (VU) based on its wider distribution along the Andean-Amazonian foothills of Colombia, Ecuador and Peru, and probably the Orinoco slope of the Andes of Colombia and Venezuela.

Abstract. Podzol-ferralsol soil systems cover great areas in Amazonia and in other equatorial regions, they are an end-member of old equatorial landscape evolution, are frequently associated with kaolin deposits and store and export large amounts of carbon. Their biogeochemistry was usually inferred from soil mineralogy and from spring or river water properties. This paper presents a database for groundwaters sampled in situ in a typical podzol-ferralsol soil catena from the Alto Rio Negro region, Brazil; the sampling periods allowed to sample under high- and low-level water-table conditions. The compositions of the groundwaters percolating the soil system are consistent with the currently observed mineral and organic paragenesis. The acidity and the site density of the dissolved organic matter (DOM) produced and circulating in the podzol white sand horizons are similar to what was observed in acid podzolic temperate zone. The aggressiveness of the white sand groundwater with regard to secondary minerals favours the podzol development at the expense of the ferralsolic or kaolin material. Some DOM is able to percolate in depth through clayey material with concentrations up to 9.7 mgC l−1 (4.0 on average). This DOM is characterized by high site densities indicating a large proportion of small carboxylic acids. In the deep kaolin and in the ferralsolic horizons, the Si and Al content of the groundwater is controlled by gibbsite and kaolinite precipitation/dissolution and by quartz dissolution. The mobility of Fe, mainly transported as Fe2+, is sensitive to small variations in EH. The bleaching of the deep kaolin at the upper part of the slopes is favoured by the high content of small carboxylic compounds and by the redox conditions of the solutions issuing from the podzolic horizons. The transfer of Al and Fe result in the precipitation of Al-nodules in slope horizons and of Fe-oxides in the upper downslope horizon. It can be inferred that thick bleached kaolin are likely everywhere presently active giant podzols are close to a slope gradient sufficient to allow deep percolation of groundwater.

Four Ecuadorian species in Calathea series Nudiscapae (Petersen) Schumann s.l. are described as new. Calathea tinalandia occurs on the Pacific slope of the Cordillera in Pichincha and Esmeraldas provinces, while C. lanicaulis, C. anderssonii, and C. clivorum occur in northeastern Ecuador in the Amazonian lowlands of Napo and Pastaza provinces.

The aim of this study was to assess precipitation (P) and actual evapotranspiration (ET) by analyzing data from in situ stations compared with remote sensing products. Climate Hazards Center InfraRed Precipitation (CHIRP) and Climate Prediction Center morphing technique (CMORPH) were used for P and Operational Simplified Surface Energy Balance (SSEBop) was used for ET. The P in situ data for six stations were also compared to a reference station in the city. ET was analyzed for a single in situ station. The region chosen for this study was the Metropolitan Area of Belem (MAB), close to the estuary of the Amazon River and the mouth of the Tocantins River. Belem is the rainiest state capital in Brazil, which causes a myriad of challenges for the local population. The assessment was performed using the statistical metrics root-mean-square error (RMSE), normalized root-mean-square error (NRMSE), mean bias error (MBE), coefficient of determination (R2), regression slope, and Nash–Sutcliffe coefficient (NS). For the reference station, the automatic and conventional CHIRP and CMORPH results, in mm/month, were as follows: automatic CHIRP: RMSE = 93.3, NRMSE = 0.32, MBE = −33.54, R2 = 0.7048, Slope = 0.945, NS = 0.5668; CMORPH: RMSE = 195.93, NRMSE = 0.37, MBE = −52.86, R2 = 0.6731, Slope = 0.93, NS = 0.4344; conventional station CHIRP: RMSE = 94.87, NRMSE = 0.32, MBE = −33.54, R2 = 0.7048, Slope = 0.945, NS = 0.5668; CMORPH: RMSE = 105.58, NRMSE = 0.38, MBE = −59.46 R2 = 0.7728, Slope = 1.007, NS = 0.4308. In the MAB region, ET ranges on average between 83 mm/month in the Amazonian summer and 112 mm/month in the Amazonian winter. This work concludes that, although CMORPH has a coarser resolution than CHIRP for the MAB at a monthly resolution, both remote sensing products were reliable. SSEBop also showed acceptable performance. For analyses of the consistency of precipitation time series, these products could provide more accurate information. The present study validates P and ET from remote sensing products with station data in the rain-dominated urban MAB.

Purpose: this work aims to analyze the factors that contributed to the intensification of erosion in the Amazon region of Buriticupu (MA) and discuss possible forms of mitigation and control. Methods: urban area of the municipality was characterized and data on soil, pedology, relief, slope, use and occupation, economic activities developed, as well as satellite images, were collected. This information was used to analyze indicators of natural erosion processes, as well as the influence of human activities. Possible mitigation and control solutions were discussed. Results and discussion: it was found that several aspects contribute to the development of erosion phenomena in the region, such as soil type, slope and hydrology. In the case of the municipality under study, geoenvironmental factors favor the development of gullies. However, the main force has been the action of man in modifying the landscape and weakening the soil. It is understood that it is necessary to implement articulated biogeoengineering strategies, such as controlling the slope and stability of slopes, the water flow regime, plant restoration and environmental education strategies. With this, we can be successful in mitigating the phenomenon and preserving the landscape. Implications of the research: it is urgent to develop shared management measures between federated entities, organized civil society and the local population to map and regulate sustainable development, especially in Amazonian regions. Originality/value: in some Amazonian regions, as in the case of the municipality of Buriticupu (MA), the advancement of agricultural activities and urban development, associated with climate change, have significantly influenced the emergence and advancement of gullies, which can promote the disappearance of the built environment. These gullies are treated as more advanced soil erosion phenomena, serious and difficult to control and remediate. Although erosion is a problem that affects many regions in Brazil, there are still few studies that aim to investigate the causes of its appearance and the discussion about possible solutions applied to gullies in the Amazon region is unprecedented. Agricultural development has accelerated soil degradation and is an urgent problem to be debated.

SummaryWe documented the geographical distributions and habitat selection of Neotropical migrants in South America along a successional gradient in the lowlands of Amazonian Peru, and along elevational gradients in the Andes of south-eastern Peru and of eastern and western Ecuador. Most of the 30 species of northern migrants that regularly winter in South America appear to be concentrated in the western edge of the Amazon basin and on the lower slopes (2,000 m) of the Andes. Migrants in a lowland site were documented more often in early successional habitats than in primary forest, and no species were confined to mature forest habitats. The number of species and relative abundance of migrants in primary forest, however, increased with elevation up to about 1,200 m and decreased above that elevation. Several species (Contopus borealis, Dendroica cerulea and Wilsonia canadensis) were largely confined to primary forest in the 1,000-2,000 m elevational zones in both Peru and Ecuador. Migrants on the western slope of the Ecuadorean Andes included several species that primarily winter further north. In general, the species richness of migrants and residents was inversely correlated, both on a biogeographical and a local scale. Migratory birds are most likely to be adversely affected by deforestation of the lower slopes of the Andes, which is proceeding at a rapid pace. The impact of human alterations of Amazonian forests will be greater on resident than on migratory birds. The loss of mid-successional lowland forests, however, might have a negative effect on several species.

Abstract The present study aims to compare the allometry and wood density of Goupia glabra Aubl. (Goupiaceae) in two different terra-firme sites in Amazonian forest. A total of 65 trees ≥ 10 cm DBH was sampled in both sites, with 39 trees in Nova Olinda do Norte (NOlinda, near the Amazon River) and 29 trees in Apuí (near the southern edge of the Amazon forest). Except for the relationship between DBH (diameter at breast height) and Ht (total height), allometric relationships for G.glabra differed significantly between sites. Apuí had lower intercept and greater slope for log10 (DBH) versus log10 (Hs – stem height), and, conversely, greater intercept and lower slope for log10 (DBH) versus log10 (Ch – crown height). The slope differed significantly between the sites for DBH versus Cd (crown diameter), with greater slope found for NOlinda. Mean basic wood density in Apuí was 8.8% lower than in NOlinda. Our findings highlight the variation in adaptive strategy of G. glabra due to environmental differences between sites. This is probably because of different canopy-understory light gradients, which result in differentiation of resource allocation between vertical and horizontal growth, which, in turn, affects mechanical support related to wood density. We also hypothesize that differences in soil fertility and disturbance regimes between sites may act concomitantly with light.

La marée interne est un phénomène complexe généré par l'interaction entre les marées de surface avec la topographie marine (monts sous-marins, pentes continentales, dorsales) dans un contexte d'océan stratifié. La dissipation de l'énergie associée à la marée interne engendre un intense mélange vertical qui influence la température de l'océan sur toute la colonne d'eau jusqu'en surface, ce qui a un impact significatif pour circulation thermohaline, pour le mélange profond, et pour la convection nuageuse, concernant le mélange plus en surface. L'ensemble des deux (marée interne et de surface) a donc un impact important sur le climat. Ce mélange influence également les concentrations en nutriments, et par ricochet la production primaire et la distribution des organismes marins. Ces divers impacts sont assez documentés dans certaines régions océaniques grâce aux données in situ et à la modélisation numérique. Mais la question de l'impact de la marée interne sur la structure de la température et des nutriments reste encore ouverte concernant la région au large de l'embouchure de l'Amazone, qui est ma zone d'étude. L'objectif premier de ma thèse, qui est technique, est de fournir une base de données de simulations numériques permettant d'étudier la dynamique de la marée interne et de son impact sur le milieu physique et la biogéochimie marine au large de l'embouchure de l'Amazone. Le second objectif, qui est scientifique, est d'utiliser ces simulations pour analyser l'impact de la marée interne sur la structure de la température et sa variabilité dans le temps. Durant ma thèse, j'ai participé à la mise en place de deux configurations du modèle NEMO dédiées à l'étude des ondes internes de marée. L'une est physique et baptisée "AMAZON36", et l'autre est couplée physique-biogéochimie avec le modèle PISCES et baptisée "AMAZON36-BIO". Ensuite, j'ai réalisé, pour chacune des deux configurations, des simulations jumelles (avec et sans forçage de marée) sur plusieurs années, 2007-2016 et 2013-2016 pour AMAZON36 et AMAZON36 -BIO, respectivement. Dans la suite de la thèse, nous avons utilisé les simulations de la configuration AMAZON36 pour montrer comment au large de l'embouchure de l'Amazone, les ondes internes de marée entrainent un refroidissement significatif de la SST qui induit une augmentation des flux net de chaleur entre l'océan et l'atmosphère sus-jacente. Les ondes internes de marée induisent également un refroidissement de la température sur la verticale à l'intérieur de l'océan, dans la couche de mélange et au-dessus de la thermocline, et un refroidissement en dessous jusqu'à plusieurs centaines de mètres. Nous avons aussi montré que c'est par le mélange vertical que les ondes internes de marée impactent la température sur toute la verticale. Dans la suite, nous avons utilisé ces simulations et des observations satellites de la température de surface de la mer (SST) pour analyser variabilité temporelle de cet impact sur la température aux fréquences semi-diurnes et bimensuelle depuis la surface jusqu'à l'intérieur de la colonne d'eau. Il apparait clairement que les ondes internes dans leurs zones de dissipation sur le talus et au large, entrainent de fortes fluctuations de température à haute fréquence pouvant atteindre plusieurs degrés Celsius, et un peu moins à l'échelle bimensuelle. Les travaux de ma thèse permettent ainsi (i) de mieux appréhender les mécanismes et les échelles temporelles d'action de la marée interne sur la température au large de l'embouchure de l'Amazone, et (ii) posent une base solide, en termes de réalisation de simulations numériques, pour l'analyse de l'impact de la marée interne sur la biogéochimie dans cette région
Internal tides (IT) are a complex phenomenon generated by the interaction between surface tides and marine topography (seamounts, continental slopes, ridges) in a stratified ocean. The dissipation of IT's energy generates an intense vertical mixing that influences the temperature of the ocean over the entire water column down to the surface, which has a significant impact on the thermohaline circulation, for the deep mixing, and for the cloud convection, concerning the mixing close to the surface. Together, they both (internal and surface tides) have a significant impact on the climate. This mixing also influences nutrient concentrations, and in turn the primary production and distribution of marine organisms. These various impacts are well documented in some ocean regions thanks to in situ data and numerical modelling. But the question of the impact of ITs on the structure of temperature and nutrients is still open regarding the region off the mouth of the Amazon, which is my study area. The primary objective of my thesis, which is technical, is to provide a database of numerical simulations to study the dynamics of ITs and their impact on the physical environment and marine biogeochemistry off the mouth of the Amazon. The second objective, which is scientific, is to use these simulations to analyze the impact of ITs on the temperature structure and its variability over time. During my thesis, I participated in the implementation of two configurations of the NEMO model dedicated to the study of ITs. One is physical and called "AMAZON36" and the other is coupled with the PISCES model and is called "AMAZON36 -BIO". Then, for each of the two configurations, I performed twin simulations (with and without tidal forcing) over several years, 2007-2016 and 2013-2016 for AMAZON36 and AMAZON36 -BIO, respectively. In the rest of the thesis, we used simulations of the AMAZON36 configuration to show how off the mouth of the Amazon, the mixing induced by the dissipation of ITs impacts the SST, the net heat flux between the ocean and the overlying atmosphere, the temperature on the vertical. And finally, what are the processes by which the internal tides act. Subsequently, we used these simulations and satellite observations of sea surface temperature (SST) to analyze the temporal variability of this impact on temperature at semi-diurnal and fortnightly frequencies from the surface to the interior of the water column. My thesis has allowed (i) to better understand the mechanisms and the temporal scales of IT's actions on the temperature off the mouth of the Amazon, and (ii) lay a solid basis for the analysis of the impact of the internal tides on biogeochemistry in this region

This volume brings together archaeologists working in Ecuador, Peru, and Bolivia to construct a new prehistory of the Upper Amazon, outlining cultural developments from the late third millennium B.C. to the Inca Empire of the sixteenth century A.D. Encompassing the forested tropical slopes of the eastern Andes as well as Andean drainage systems that connect to the Amazon River basin, this vast region has been unevenly studied due to the restrictions of national borders, remote site locations, and limited interpretive models. The Archaeology of the Upper Amazon unites and builds on recent field investigations that have found evidence of extensive interaction networks along the major rivers—Santiago, Marañon, Huallaga, and Ucayali. Chapters detail how these rivers facilitated the movement of people, resources, and ideas between the Andean highlands and the Amazonian lowlands. Contributors demonstrate that the Upper Amazon was not a peripheral zone but a locus for complex societal developments. Reaching across geographical, cultural, and political boundaries, this volume shows that the trajectory of Andean civilization cannot be fully understood without a nuanced perspective on the region’s diverse patterns of interaction with the Upper Amazon.

Abstract Most raised fields provide for drainage by means of elevated surfaces in association with surrounding ditches which catch water, drain subsoils, and in some instances remove water from the field vicinity, both on flats and on slopes. In addition, there are examples of drainage by ditching alone without raised planting surfaces or with only minimal raising from earth removed from narrow, shallow ditches. Some of the prehistoric Mayan drained fields in Belize are believed to be primarily ditched or channelized fields (Turner 1983; Pohl and Bloom 1996).

Abstract Agricultural technology and the human management of the natural environment for the cultivation of domesticated plants, involves crops, tools, and the processes and forms of environmental modification. Agricultural fields can be divided into those that are artificial in terms of significant degree of surface modification and those that are not. The latter are usually rainfed or located where water is concentrated; they often have good soils; and they are mostly on gentle slopes. However, for past times our best evidence is the forms of manmade agricultural features (agricultural landforms)1 which have survived, and these are given major attention in this study. They consist of actual fields and/or field features such as canals. In addition, there are aspects of technology that do not survive visually, but may be detected through stratigraphy, chemical analysis of soil, palynology, and other archaeological means, as well as from written accounts and observation of current practices. These include soil management, vegetation control, use of fire, etc.

Terra firme forests are those that by definition are not permanently or seasonally flooded (terra firme meaning “firm terrain”). This type of forest encompasses the Amazon and Orinoco basins, stretching from the lower slopes of the Andes, east to the Guianas, and south to about 15°S in western Brazil and northern Bolivia (Richards 1996). Structural and compositional variability in these forests in the Amazon basin is very wide as a result of climate differences and geomorphological position. The region is not climatically uniform; the central and much of the southern parts have less and more seasonal rainfall than the eastern and western parts (Walsh 1996). These differences have direct and indirect ecological significance, as phenology and biological processes related to nutrient availability will be strongly influenced by both factors (Cuevas and Medina 1986, 1988, 1990, Medina and Cuevas 1989). Periods of two or more consecutive dry days are ecologically significant in a humid area such as San Carlos de Río Negro, in the northern part of the Amazon, because of low water retention capacity in the widespread sandy soils. In lower geomorphological positions, dry spells of 5-10 days may result in fluctuations of the water table from 0.4-1.0 m (Herrera 1977, Bongers et al. 1985). In areas with a more strongly seasonal climate, roots have been found extending to 18 m depth (Nepstad et al. 1995). This may explain the presence of evergreen forest in the seasonally dry eastern Amazon. Structure and physiognomy of terra firme forests is very similar throughout Amazonia, but floristically it is quite variable due to different compositions in the subbasins of the Amazon’s major tributaries. These subbasins are located within geochemical regions that can be differentiated based on the physicochemical properties of drainage waters (Sioli 1975, Fittkau 1971, Fittkau et al. 1975). Blackwater rivers, such as the Río Negro, drain mostly sandy podsolized soils low in most essential nutrients for plant growth. They are characterized by a high content of humic acids, which remain dissolved because of the predominant low concentrations of polyvalent cations, mainly Ca2+ and Mg2+.

An early identification of geo-hazards i.e. slides, fluvial erosion, eolic erosion, rainwater erosion among others and the subsequent mitigation and remediation of its effects on the Right of Way (ROW) and the pipelines, has prevented the occurrence of leaks in the Camisea NG and NGL Transportation System, which includes a 730 Km natural gas pipeline and a parallel 560 Km natural gas liquids pipeline, operated and maintained by Compan˜i´a de Gas del Amazonas (COGA). The Camisea Transportation System, traverse the Peruvian territory starting in Malvinas (Cusco). The NGL pipeline stops in Playa Loberi´a (Ica) and the NG pipeline stops in the City Gate, located in Luri´n (Lima). These pipelines traverse the Peruvian rainforest, the Andes Mountains and coastal areas. The intend of this paper is to describe the use of a Risk Matrix (RM) in order to calculate different risk levels for the prioritization of the geotechnical mitigation and stabilization works to be performed during the dry season of the Peruvian rainforest. The RM is a tool based on the so-called Safety Ratio, incorporating calculation parameters of the Security Factor used in the stability analysis of slopes. Once the work sites have been identified using the RM, the engineering design is performed, using geotechnical engineering techniques such as subsoil exploration, laboratory testing, mathematic modeling, designs and instrumentation. After the Geotechnical Engineering process has been completed, the Safety Ratio values estimated with the RM are replaced by Safety Factors. The paper concludes showing the benefits of the whole Risk Management System, which has been successfully applied in the first 200 Km of the ROW characterized by residual soils, slopes with more than 45° and 7000 mm in excess of rainfall per year.