Amazon Basin Research Articles

Selectivity of gillnets on the main fish species caught in the floodplains of the Madeira River (Rondônia, Brazil)

Small-scale fishing in the floodplains of the Amazon basin has intensified, with gillnets being one of the main types of tackle used. In this study, we evaluated the length structure of fish species in a floodplain lake of the Madeira River basin, emphasizing the selectivity of the nets in the main species caught. The fisheries were collected in periods of high water and low water, with nets of mesh sizes of 40, 60, 80, 100, 120 and 160 mm. Tests between the periods and also comparing the meshes were performed and the parameters of the selectivity curves estimated with the SELECT calculation code. Records of 17 new maximum lengths are presented. Of the 12 most abundant species, the selectivity of the nets in the modal lengths for Anchovia surinamensis were 13.3, 19.9, 26.6 and 33.2 cm in the nets with mesh sizes of 40, 60, 80 and 100 mm, respectively. In the three smallest mesh sizes, the values for Potamorhina altamazonica were 12.7, 19.0 and 25.3 cm and for Pellona flavipinnis values were 15.4, 23.2 and 30.9 cm. In the two smallest mesh sizes, the following values were presented for the species Potamorhina latior (12.9 and 19.4 cm), Potamorhina rutiloides (11.3 and 16.9 cm), Triportheus elongatus (19.7 and 29.5 cm), Triportheus flavus (14.1 and 21.1 cm) and Pimelodus blochii (15.5 and 23.0 cm). The estimates of selectivity of the nets, in addition to being basic information for fishery sciences, are also fundamental for the management of Amazonian fish stocks.

An automated procedure to determine construction year of roads in forested landscapes using a least‐cost path and a Before‐After Control‐Impact approach

AbstractProximity to roads is one of the main determinants of deforestation in the Amazon basin. Determining the construction year of roads (CYR) is critical to improve the understanding of the drivers of road construction and to enable predictions of the expansion of the road network and its consequent impact on ecosystems. While recent artificial intelligence approaches have been successfully used for road extraction, they have typically relied on high spatial‐resolution imagery, precluding their adoption for the determination of CYR for older roads. In this article, we developed a new approach to automate the process of determining CYR that relies on the approximate position of the current road network and a time‐series of the proportion of exposed soil based on the multidecadal remote sensing imagery from the Landsat program. Starting with these inputs, our methodology relies on the Least Cost Path algorithm to co‐register the road network and on a Before‐After Control‐Impact design to circumvent the inherent image‐to‐image variability in the estimated amount of exposed soil. We demonstrate this approach for a 357 000 km2 area around the Transamazon highway (BR‐230) in the Brazilian Amazon, encompassing 36 240 road segments. The reliability of this approach is assessed by comparing the estimated CYR using our approach to the observed CYR based on a time‐series of Landsat images. This exercise reveals a close correspondence between the estimated and observed CYR (). Finally, we show how these data can be used to assess the effectiveness of protected areas (PAs) in reducing the yearly rate of road construction and thus their vulnerability to future degradation. In particular, we find that integral protection PAs in this region were generally more effective in reducing the expansion of the road network when compared to sustainable use PAs.

Chemical composition of guarana flowers and nectar and their ecological significance

The plant species Paullinia cupana Kunth (Sapindaceae), commonly known as guarana, originates from the central Amazonian Basin and has a long history of local use for its stimulant properties. It is currently commercialized worldwide for its health beneficial properties. The seeds chemical composition has been extensively studied over the years. However, the chemistry of guarana flowers, particularly the nectar content, have been barely investigated. From an ecological perspective, floral nectar and pollen are the primary food rewards for pollinators. In the present study, we investigated the chemical composition of nectar and whole pistillate, and staminate guarana flowers harvested separately. Although guarana is well known for its high concentration of caffeine in its seeds, to the best of our knowledge, this is the first report of caffeine and other methylxanthines as the main constituents of the nectar. The significant difference between guarana floral chemistry, which is more diverse and complex, and nectar chemical profile, which primarily contains methylxanthines, suggests that the presence of these compounds in guarana nectar may have an impact on plant-pollinator interactions, which can affect the fitness of both plants and flower visitors

Orientatractis bowseri n. sp. (Nematoda: Cosmocercoidea: Atractidae) parasite of Peltocephalus dumerilianus (Schweigger) (Testudines: Podocnemididae) from the Brazilian Amazon.

Peltocephalus dumerilianus (Schweigger) is a diurnal freshwater turtle widely distributed in the Orinoco and Amazon River basins in Brazil, Colombia, Peru, Ecuador, Venezuela, and French Guiana. During a helminthological survey of freshwater turtles from the Brazilian Amazon, numerous nematodes with characteristics of the genus Orientatractis Petter, 1966 were recovered from the stomach of Peltocephalus dumerilianus. These nematodes were different from all congeneric species, and we describe herein. Orientatractis bowseri n. sp. differs from all known species of the genus by having dorsal cuticular projections on the posterior region of the females, distribution of caudal papillae and by having papilla-like ornamentations on the cuticle distributed from the mid-esophagus to the mid portion of the body. This study represents the fourth specie of the genus Orientatractis reported in Brazil, the seventh species of Orientatractis in the Neotropical region, and the third found infecting freshwater turtles in Brazil.

Soil phosphorus cycling across a 100-year deforestation chronosequence in the Amazon rainforest.

Deforestation of tropical rainforests is a major land use change that alters terrestrial biogeochemical cycling at local to global scales. Deforestation and subsequent reforestation are likely to impact soil phosphorus (P) cycling, which in P-limited ecosystems such as the Amazon basin has implications for long-term productivity. We used a 100-year replicated observational chronosequence of primary forest conversion to pasture, as well as a 13-year-old secondary forest, to test land use change and duration effects on soil P dynamics in the Amazon basin. By combining sequential extraction and P K-edge X-ray absorption near edge structure (XANES) spectroscopy with soil phosphatase activity assays, we assessed pools and process rates of P cycling in surface soils (0-10 cm depth). Deforestation caused increases in total P (135-398 mg kg-1 ), total organic P (Po ) (19-168 mg kg-1 ), and total inorganic P (Pi ) (30-113 mg kg-1 ) fractions in surface soils with pasture age, with concomitant increases in Pi fractions corroborated by sequential fractionation and XANES spectroscopy. Soil non-labile Po (10-148 mg kg-1 ) increased disproportionately compared to labile Po (from 4-5 to 7-13 mg kg-1 ). Soil phosphomonoesterase and phosphodiesterase binding affinity (Km ) decreased while the specificity constant (Ka ) increased by 83%-159% in 39-100y pastures. Soil P pools and process rates reverted to magnitudes similar to primary forests within 13 years of pasture abandonment. However, the relatively short but representative pre-abandonment pasture duration of our secondary forest may not have entailed significant deforestation effects on soil P cycling, highlighting the need to consider both pasture duration and reforestation age in evaluations of Amazon land use legacies. Although the space-for-time substitution design can entail variation in the initial soil P pools due to atmospheric P deposition, soil properties, and/or primary forest growth, the trend of P pools and process rates with pasture age still provides valuable insights.

Fine root presence and increased phosphorus availability stimulate wood decay in a central Amazonian rainforest

In the Amazon basin, approximately 60% of rainforest thrives on geologically old and highly weathered soils, thus decomposition represents an important mechanism for recycling nutrients from organic matter. Although dead logs and branches constitute up to 14% of the carbon stored in terrestrial ecosystems, woody debris decomposition and mainly the effect of direct nutrient cycling by plant root interaction is poorly studied and often overlooked in ecosystem carbon and nutrient budgets. Here we monitored the decomposition of five different local woody species covering a range of wood density by conducting a long‐term wood decomposition experiment over two years with factorial root presence and phosphorous (P) addition treatments in a central Amazonian rainforest. We hypothesized that woody debris decomposition is accelerated by colonizing fine roots mining for nutrients, possibly strongly affecting wood debris with lower density and higher nutrient concentration (P). We found that root colonization and P addition separately increased wood decay rates, and although fine root colonization increased when P was added, this did not result in a change in wood decay. Nutrient loss from wood was accelerated by P addition, whereas a root presence effect on nutrient mobilization was only detectable at the end of the experiment. Our results highlight the role of fine roots in priming wood decay, although direct nutrient acquisition by plants seems to only occur in more advanced stages of decomposition. On the other hand, the positive effect of P addition may indicate that microbial nutrient mobilization in woody material is driven mainly by wood stoichiometry rather than priming by root activity.

Evaluation of the management potential of timber resources in clearwater floodplain forests in the Amazon using growth models

The Amazonian clearwater igapós are poorly studied floodplain ecosystems that are mainly covered by forests and are undergoing massive threats due to changes in land use and climate. Their hydrochemical characteristics and edaphic conditions fall between those of the eutrophic várzea floodplains on whitewater rivers and those of the oligotrophic igapós on blackwater rivers. Previous studies have indicated the management potential of timber species in the highly dynamic várzea floodplains due to the fast tree growth and high forest productivity. Timber resource management, however, is not recommended for the blackwater ecosystem because of its slow dynamics and high vulnerability to disturbances. For clearwater igapós, information on the potential for sustainable management of timber resources is lacking. In this study, we modeled the growth in diameter, height, and volume to derive species-specific minimum logging diameters (MLD) and felling cycles (FC) for eight merchantable species in the clearwater igapós of the Branco and Tapajós rivers in the northern and southern Amazon Basin, respectively. Diameter growth was modeled by analyzing the tree rings that are annually formed in the Amazonian floodplains as a consequence of the regular and predicable long-term flooding. Growth modeling followed the guidelines of the Growth-Oriented Logging (GOL) concept, with the adjustment of diameter growth improved by applying nonlinear mixed-effects regression. MLDs varied from 36 to 90 cm and FCs ranged from 6 to 21 years, which diverges from the standards of Brazilian logging regulations (MLD: 50 cm; FC: 25–35 years). This indicates the potential for timber resource management, which should be tested and introduced at small scales, integrated in protected areas to stepwise promote the sustainable management of these natural resources by traditional communities to increase their income and the conservation of this ecosystem.

Hydrological Response Assessment of Land Cover Change in a Peruvian Amazonian Basin Impacted by Deforestation Using the SWAT Model

The watershed hydrologic conditions in the Madre de Dios (MDD) Basin in the Peruvian Amazon have been irreversibly impacted by deforestation and changes in land cover. These changes have also had detrimental effects on the geomorphology, water quality, and aquatic habitat within the basin. However, there is a scarcity of hydrological modeling studies in this area, primarily due to the limited availability of hydrometeorological data. The primary objective of this study was to examine how deforestation impacts the hydrological conditions in the MDD Basin. By implementing the Soil and Water Assessment Tool (SWAT) model, this study determined that replacing 12% of the evergreen broadleaf forest area with bare land resulted in a significant increase in surface runoff, by 38% monthly, a 1% annual reduction of evapotranspiration, and an average monthly streamflow increase of 12%. Changes in spatial patterns reveal that the primary impacted watershed is the Inambari River subbasin, a significant tributary of the Madre de Dios River. This area experiences an annual average surge of 187% in surface runoff generation while witnessing an annual average reduction of 8% in evapotranspiration. These findings have important implications, as they can contribute to instances of flooding and extreme inundation events, which have already occurred in the MDD region.

Towards a productive model for the Sacha Inchi value chain: A scientometric approach

The diversification of agricultural and livestock production matrixes has the potential to generate value-added products in industrial and promising crops. Specifically, the countries in the Amazon basin have in the Sacha Inchi (Plukenetia volubilis L.) a species oriented toward market niches such as food, oils, cosmetics, pharmaceuticals, and biofuels, whose exploitation and use are aligned with the bioeconomy and circular economy megatrends. The aim of this publication was to identify and analyze the evolution of scientific and technological research in the Sacha Inchi value chain worldwide, based on a methodological design that combines technological intelligence, the analysis of scientific landscapes and bibliometric indicators and content analysis, to establish a baseline for the identification of key elements for the design of an agro-industrial production model. The methodology includes the integration of surveillance and scientific intelligence methods, scientometrics, and critical analysis of key documents selected through bibliometric indicators and expert judgment. The analysis made it possible to identify the research development lines in Sacha Inchi worldwide, and the reference documents that comprise key elements of the activities from cultivation to processing of the product obtained. The basic investigations identified will contribute to the development of productive models of Sacha Inchi in Colombia, where technical aspects must be adapted or validated in suitable agroecological zones or with productive potential to improve the yield and quality of seed for agroindustry. Medium-term research is required to genetically identify the planting material, to facilitate the selection of materials oriented to the production of fruits with the quality required by the agroindustry.

Remote sensing evidence for population growth of isolated indigenous societies in Amazonia

Isolated indigenous societies who actively avoid sustained peaceful contact with the outside world are critically endangered. Last year, “Tanaru”, the lone surviving man of his tribe for at least 35 years, died in Southwest Amazonia, marking the latest cultural extinction event in a long history of massacres, enslavement, and epidemics. Yet in the upper reaches of the Amazon Basin, dozens of resilient isolated tribes still manage to survive. Remote sensing is a reliable method of monitoring the population dynamics of uncontacted populations by quantifying the area cleared for gardens and villages, along with the fire detections associated with the burning of those clearings. Remote sensing also provides a method to document the number of residential structures and village fissioning. Only with these longitudinal assessments can we better evaluate the current no-contact policies by the United Nations and governments, along with the prospects for the long-term survival of isolated tribes. While the world’s largest isolated indigenous metapopulation, Pano speakers in Acre, Brazil, appears to be thriving, other smaller isolated populations disconnected from metapopulations continue to be extremely vulnerable to external threats. Our applied anthropological conservation approach is to provide analyses of publicly available remote sensing datasets to help inform policies that enhance the survival and well-being of isolated cultural groups.

Tree growth performance and xylem functional arrangements of Macrolobium Schreb. (Fabaceae) in different wetland forests in the Central Amazon basin

Tree growth performance and xylem functional arrangements of Macrolobium Schreb. (Fabaceae) in different wetland forests in the Central Amazon basin

Tracking Mesoscale Convective Systems in IMERG and Regional Variability of Their Properties in the Tropics

AbstractMesoscale convective systems (MCSs) constitute only a fraction of convective systems in the tropics but significantly impact tropical weather and global climate. Early studies used satellite infrared (IR) data to track MCSs and study their properties but only for a short period due to computing limitations. Though valuable, the IR brightness temperature (Tb)‐derived precipitation properties have biases. The recent availability of Integrated Multi‐satEllite Retrieval for Global (IMERG) precipitation mission rainfall data of lesser bias than IR Tb‐based rainfall and access to high‐performance computers motivated us to track MCSs over global tropics for 10 years, using the Forward in Time (FiT) algorithm. Though IMERG is advantageous, it poses challenges to tracking MCSs due to convective systems connected by light rain areas and resolution differences between contributing passive microwave sensors. The precipitation field is smoothed and normalized to overcome these problems; then, the FiT algorithm identifies MCSs and tracks them. Our results show that MCSs contribute ∼70% of annual precipitation, though they are only ∼7% of all tracked systems. MCSs occur more often over the Amazon basin and Maritime Continent than in central Africa, known for high thunderstorm frequency, highlighting the contrasting convective regimes. The large, long‐lived, and intensely precipitating MCSs occur more often over the ocean than land, except for the Amazon basin. Fast‐moving MCSs often occur over West Africa, the Amazon basin, and the western Pacific, whereas slow‐moving MCSs are common over Colombia and the Maritime Continent.

Reconstruction of glaciers in the western boundary of the Altiplano (18.5°-19°S): Singularities and insights on potential drivers of past advances

Today, glaciers in the western Altiplano are very scarce, even on peaks exceeding 6000 m. In this mostly ice-free landscape, however, moraines and other glacial deposits are commonly found attesting to quite different climate conditions that favored the advance of glaciers in the past. Although other areas of the Altiplano have been commonly accounted for regarding paleoclimate reconstructions, western Altiplano has been often overlooked. Here we present a detailed map of glacial landforms and a paleoglacier reconstruction from a test area in the western Altiplano between 18.5° and 19°S. We reconstructed regional equilibrium line altitudes (ELA) for several moraine stages, representing extensive past glacier advances in the region. During a prominent and ubiquitous ‘Principal Moraine (PM)’ stage glaciers from most peaks and all orientations advanced to altitudes of up to 4000 m asl. Reconstructed PM ELAs along 90 valleys range from 4400 to 5000 m asl. ELA distribution reveals a strong aspect-dependency at the western boundary of the Altiplano, with ELAs 300 m lower on west-facing glaciers than east-facing glaciers. The coincidence of such steep gradient with a prominent NW-SE ridge accounts for topographic control on the precipitation and thus in the advance of glaciers along the western boundary of the Altiplano. To the east, ELAs from the peaks towering the Altiplano are comparable to ELAs from east-facing glaciers at the western Altiplano boundary but show little to no aspect-dependency. Since these patterns cannot be solely explained by increased moisture advection from the Amazon basin, we suspect that western-sourced moisture associated with increased frequency of cold fronts and cut-off events played an important role in the glacier dynamics at this latitude. Nevertheless, further investigations are required to evaluate the relative role of both precipitation regimes on the glacier dynamics from the westernmost Altiplano.

Harvesting Bertholletia excelsa Bonpl. in a western Amazon rural community: local ecological knowledge and meaning to “nut-crackers”

IntroductionThe collection of Bertholletia excelsa Bonpl. (castanha-da-Amazônia; Brazil nuts) seeds make up part of the everyday activities of the traditional populations that have inhabited all of the Amazon basin since remote times. Nonetheless, knowledge about these harvesting activities in native forest areas has not been well documented. The present study was designed to better understand the significance of this harvesting activity as well as the traditional ecological knowledge of the harvesters.MethodsUtilizamos entrevistas semiestruturadas para a coleta de dados com extrativistas de castanha, moradores de Caroebe, Roraima (n = 18) durante o período de março de 2021 a março de 2022. The data analysis was based on the frequency of responses to socio-economic questions and their knowledge about that plant species as well as why those interviewees chose that line of work. We also adopted the Spearman and Mann–Whitney non-parametric tests to correlate variables identified in the study, and selected sections of their depositions to highlight the traditional knowledge of the interviewees and their experiences as harvesters.ResultsConstatamos que as razões para a escolha do trabalho com o extrativismo para todos os entrevistados é a necessidade de renda complementar, tradição familiar (55%), the sense of well-being provided by contact with the natural environment (25%), and a favorable disposition toward that type of work (11%). Harvesting involves collective work, and many of the interviewees had engaged in those efforts to help their families since their childhood or adolescence. The older harvesters cited more animal species that consumed the Brazil nuts (ρ = 0.60; p = 0.009) and perceived more and greater changes in the environment that were prejudicial to the Brazil nut trees (U = 9.50; p = 0.022). The interviewees who reported lower incomes cited more significant cultural changes and more suggestions concerning conservation activities. According to their statements, deforestation, and the burning and illegal cutting of native trees, including Brazil nut trees, have contributed to environmental change in the region and raised significant concerns about the future of harvesting activities.ConclusionThe activities of the “nut-crackers” represent to them more than just a simple source of income, as harvesting provides them with a connection to nature that promotes their well-being and cultural heritage. The nut harvesters have gained specific knowledge concerning both environmental and cultural changes. Those changes have mainly come about through the expansion of agricultural activities and the felling of native forests—which are the main threats to the future of Brazil nut extraction. Attributing value to the folk knowledge of those harvesters would strengthen the local economy, promote forest conservation, and help to better understand the impacts of anthropic activities on the forest and the harvesting of natural products.

Influence of a hydroelectric dam on fish mercury contamination along the Sinnamary River (French Guiana)

The Petit Saut hydroelectric dam and the upstream and downstream areas of the Sinnamary River in French Guiana (Amazon basin) have been studied from 1993 to 2020. The nearly thirty-years-long study of the monitoring of total mercury concentration in fish and the physicochemical survey of the environment made it possible to demonstrate the impact of the flooding of the forest and the role of the hydroelectric dam on the methylation of mercury. Results show that the physicochemical modifications generated by the construction of the dam led to a significant production of methylmercury (MeHg) in the anoxic part of the reservoir and downstream of the river leading to a strong spatio-temporal impact of the dam. Seven species of fishes are studied and their mercury concentrations vary according to many parameters: fish diet, position in the water column, site, lake oxycline level and time.

Comparison Link Function from Summer Rainfall Network in Amazon Basin

The Amazon Basin is the largest rainforest in the world, and studying the rainfall in this region is crucial for understanding the functioning of the entire rainforest ecosystem and its role in regulating the regional and global climate. This work is part of the application of complex networks, which refer to a network modeled by graphs and are characterized by their high versatility, as well as the extraction of key information from the system under study. The main objective of this article is to examine the precipitation system in the Amazon basin during the austral summer. The networks are defined by nodes and connections, where each node represents a precipitation time series, while the connections can be represented by different similarity functions. For this study, three rainfall networks were created, which differ based on the correlation function used (Pearson, Spearman, and Kendall). By comparing these networks, we can identify the most effective method for analyzing the data and gain a better understanding of rainfall’s spatial structure, thereby enhancing our knowledge of its impact on different Amazon basin regions. The results reveal the presence of three important regions in the Amazon basin. Two areas were identified in the northeast and northwest, showing incursions of warm and humid winds from the oceans and favoring the occurrence of large mesoscale systems, such as squall lines. Additionally, the eastern part of the central Andes may indicate an outflow region from the basin with winds directed toward subtropical latitudes. The networks showed a high level of activity and participation in the center of the Amazon basin and east of the Andes. Regarding information transmission, the betweenness centrality identified the main pathways within a basin, and some of these are directly related to certain rivers, such as the Amazon, Purus, and Madeira. Indicating the relationship between rainfall and the presence of water bodies. Finally, it suggests that the Spearman and Kendall correlation produced the most promising results. Although they showed similar spatial patterns, the major difference was found in the identification of communities, this is due to the meridional differences in the network’s response. Overall, these findings highlight the importance of carefully selecting appropriate techniques and methods when analyzing complex networks.

A new annual killifish, Moema beltramonorum (Cyprinodontiformes: Rivulidae) from the Amazon basin, Bolivia.

A new annual killifish species, Moema beltramonorum, is described from a seasonal swamp next to arroyo Crespo, belonging to Ro San Martin, a tributary of Ro Itnez, Amazon River basin, Bolivia. The new taxon presents an unique combination of male colour pattern characters not present in any congener, and an unique caudal fin coloration.

Fauna of metazoan parasites of Pterygoplichthys pardalis (Castelnau, 1855) sold at fairs in the city of Manaus, state of Amazonas, Brazil

Pterygoplichthys pardalis is an endemic as well as economically important fish species in the Amazon basin. Thirty P. pardalis specimens were purchased at assorted fairs in the city of Manaus. Fish were necropsied, and then, had their organs investigated for parasites. The identified parasites were observed under Light bright field microscopy and that of Scanning Electron Microscopy (SEM). Through the analyses it was observed 219 metazoan parasite specimens, belonging to four taxonomic groups: Monogenoidea, Digenea, Acanthocephala, and Copepoda. Six metazoan parasitic species were identified: Monogenoidea Unilatus unilatus Mizelle and Kritsky, 1967 and Copepoda Therodamas elongatus (Thatcher, 1986) from the gills, Digenea Austrodiplostomum compactum (Lutz, 1928), Megacoelium spinicavum Szidat, 1954 and Diplostomum sp. from the eyes, stomach, and gonads, respectively, and Acanthocephala Gorytocephalus elongorchis Thatcher, 1979 from the intestine. Gorytocephalus elongorchis was the one presenting the highest prevalence value, followed by digeneans M. spinicavum, Diplostomum sp., and A. compactum. The present study has come to provide the very first SEM M. spinicavum, G. elongorchis, and T. elongatus images, thus improving on the up to now available data addressing P. pardalis parasitic fauna, which has been found to be infecting, the fish species presently being marketed in Manaus. Moreover, the current survey has demonstrated the identified parasite species pose no public health concern at all.

Fire-human-climate interactions in the Bolivian Amazon rainforest ecotone from the Last Glacial Maximum to late Holocene

The Amazon Rainforest Ecotone (the ARF-Ecotone) of the southwestern Amazon Basin is a transitional landscape from tropical evergreen rainforests and seasonally flooded savannahs to savannah woodlands and semi-deciduous dry forests. While fire activity plays an integral role in ARF-Ecotones, recent interactions between human activity and increased temperatures and prolonged droughts driven by anthropogenic climate change threaten to accelerate habitat transformation through positive feedbacks, increasing future fire susceptibility, fuel loads, and fire intensity. The long-term factors driving fire in the ARF-Ecotone remain poorly understood because of the challenge of disentangling the effects of prolonged climatic variability since the Last Glacial Maximum (LGM; ~24,000 to 11,000 cal BP) and over 10,500 years of human occupation in the region. To investigate this issue, we implement an interdisciplinary framework incorporating multiple lake sediment cores, with varying basin characteristics with existing regional palaeoclimatological and archaeological data. These data indicate expansive C4 grasslands coupled with low fire activity during the LGM, higher sensitivity of small basins to detecting local-scale fire activity, and increased spatial diversity of fire during the Holocene (~10,500 cal year BP to the limit of our records ~4,000 cal year BP), despite a similar regional climate. This may be attributed to increased human-driven fire. These data raise the intriguing possibility that the composition of modern flora at NKMNP developed as part of a co-evolutionary process between people and plants that started at the beginning of the ARE occupation.

Does climate change alter the nutrient trends of Cedrela fissilis Vell. trees in the southern Brazilian Amazon?

BackgroundThe increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin. An eco-nutritional approach using X-ray fluorescence micro-analysis (µXRF) is proposed to verify the long- and short-term effects of droughts on the growth and xylem nutrient concentrations of Cedrela fissilis Vell.MethodsFourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner. Profiles of ring width, wood density, and concentrations of aluminum (Al), phosphorus (P), sulfur (S), calcium (Ca), potassium (K), manganese (Mn), iron (Fe) and strontium (Sr) together with Al/Ca, Ca/Mn, K/Ca, Sr/Ca and Mn/S ratios were constructed and correlated with precipitation, temperature, the difference between precipitation and potential evapotranspiration (P-PET) and standardized precipitation–evapotranspiration index (SPEI).ResultsDuring dry years, C. fissilis showed narrower, less dense rings, lower Al, P, S and Ca, and higher K and Fe concentrations (the opposite was found in wet years). Ring width decreased (together with Al, P, S, K, Ca, Mn, Fe, Sr, Al/Ca, K/Ca and Sr/Ca) and wood density increased (together with Ca/Mn and Mn/S), which was associated with an increase in evapotranspiration and temperature over time, mainly since 1990. Cedrela fissilis showed a tendency to increase its capacity for resistance, and a recovery and resilience in growth over time associated with responses in Al, Ca, P and S. However, it showed a risk in the capacity for recovery of the pre-drought density values, associated with unsatisfactory responses in Al, Ca, K, Fe and P.ConclusionsThis study is the first attempt to analyze tree-ring nutritional evidences of C. fissilis trees to climate sensitivity and resilience to drought, based on long-term data from seasonal moist tropical forests of the Amazon. Our data suggested that C. fissilis is undergoing alterations in the concentration, use and redistribution of nutrients associated with increasing wood density and decreasing growth over time, due to the increase of drought frequency in the southern Amazon.