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The Amazon forest has the highest biodiversity on Earth. However, information on Amazonian vertebrate diversity is still deficient and scattered across the published, peer‐reviewed, and gray literature and in unpublished raw data. Camera traps are an effective non‐invasive method of surveying vertebrates, applicable to different scales of time and space. In this study, we organized and standardized camera trap records from different Amazon regions to compile the most extensive data set of inventories of mammal, bird, and reptile species ever assembled for the area. The complete data set comprises 154,123 records of 317 species (185 birds, 119 mammals, and 13 reptiles) gathered from surveys from the Amazonian portion of eight countries (Brazil, Bolivia, Colombia, Ecuador, French Guiana, Peru, Suriname, and Venezuela). The most frequently recorded species per taxa were: mammals: Cuniculus paca (11,907 records); birds: Pauxi tuberosa (3713 records); and reptiles: Tupinambis teguixin (716 records). The information detailed in this data paper opens up opportunities for new ecological studies at different spatial and temporal scales, allowing for a more accurate evaluation of the effects of habitat loss, fragmentation, climate change, and other human‐mediated defaunation processes in one of the most important and threatened tropical environments in the world. The data set is not copyright restricted; please cite this data paper when using its data in publications and we also request that researchers and educators inform us of how they are using these data. [ABSTRACT FROM AUTHOR]

The Amazon Forest, the largest contiguous tropical forest in the world, stores a significant fraction of the carbon on land. Changes in climate and land use affect total carbon stocks, making it critical to continuously update and revise the best estimates for the region, particularly considering changes in forest dynamics. Forest inventory data cover only a tiny fraction of the Amazon region, and the coverage is not sufficient to ensure reliable data interpolation and validation. This paper presents a new forest above-ground biomass map for the Brazilian Amazon and the associated uncertainty both with a resolution of 250 meters and baseline for the satellite dataset the year of 2016 (i.e., the year of the satellite observation). A significant increase in data availability from forest inventories and remote sensing has enabled progress towards high-resolution biomass estimates. This work uses the largest airborne LiDAR database ever collected in the Amazon, mapping 360,000 km2 through transects distributed in all vegetation categories in the region. The map uses airborne laser scanning (ALS) data calibrated by field forest inventories that are extrapolated to the region using a machine learning approach with inputs from Synthetic Aperture Radar (PALSAR), vegetation indices obtained from the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite, and precipitation information from the Tropical Rainfall Measuring Mission (TRMM). A total of 174 field inventories geolocated using a Differential Global Positioning System (DGPS) were used to validate the biomass estimations. The experimental design allowed for a comprehensive representation of several vegetation types, producing an above-ground biomass map varying from a maximum value of 518 Mg ha−1, a mean of 174 Mg ha−1, and a standard deviation of 102 Mg ha−1. This unique dataset enabled a better representation of the regional distribution of the forest biomass and structure, providing further studies and critical information for decision-making concerning forest conservation, planning, carbon emissions estimate, and mechanisms for supporting carbon emissions reductions. [ABSTRACT FROM AUTHOR]

We present a thorough analysis of the scientific production in climate change and adaptation in Brazil. We conducted a bibliometric and bibliographic review to reveal and discuss how climate change research has been carried out. We compared a broader climate change research dataset with a more specific climate adaptation research dataset, to understand the main differences and convergence points, and how science conducted from a mitigation and adaptation perspective demonstrates potential to confront the climate change challenges and drivers in Brazil. Four main clusters of investigation within climate change were detected: (1) impacts on forest and plant development, (2) land use and ecology, (3) adaptation/governance, and (4) climate/atmospheric studies. Only about 5% of the total studies on climate change address adaptation, for which three main clusters of research were identified: (1) adaptation actions and policies; (2) urban environment, vulnerability, and health and (3) food and coastal impacts. Although there are strong research trends in climate change for the Amazon Forest, there was less evidence of studies concerning climate adaptation for this and other Brazilian biomes, smaller cities, rural and traditional communities, and poorer regions. Our results shed a light on the more commonly chosen research topics, their strongest points and potential gaps and trends. This can contribute to the scientific communication and implementation of climate actions in Brazil, and a better understanding of the climate science knowledge from the perspective of a middle-income country. [ABSTRACT FROM AUTHOR]

The Amazon River, its huge basin, and the changes in biological processes that are rapidly occurring in this region are unquestionably of global significance. Hence, Global Change Biology is delighted to host a special thematic issue devoted to the Large-scale Biosphere-Atmosphere Experiment in Amazônia (LBA), which is a multinational, interdisciplinary research program led by Brazil. The goal of LBA is no less modest than its subject: to understand how Amazônia functions as a regional entity in the Earth system and how these functions are changing as a result of ongoing changes in land use. This compilation of 26 papers resulting from LBA-related research covers a broad range of topics: forest stocks of carbon (C) and nitrogen (N); fluxes of greenhouse gases and volatile organic compounds from vegetation, soils and wetlands; mapping and modeling land-use change, fire risk, and soil properties; measuring changes caused by logging, pasturing and cultivating; and new research approaches in meteorology to estimate nocturnal fluxes of C from forests and pastures. Some important new synthesis can be derived from these and other studies. The aboveground biomass of intact Amazonian forests appears to be a sink for atmospheric carbon dioxide (CO2), while the wetlands and soils are a net source of atmospheric methane (CH4) and nitrous oxide (N2O), respectively. Land-use change has, so far, had only a minor effect on basin-wide emissions of CH4 and N2O, but the net effect of deforestation and reforestation appears to be a significant net release of CO2 to the atmosphere. The sum of the 100-year global warming potentials (GWP) of these annual sources and sinks of CH4, N2O, and CO2 indicate that the Amazonian forest-river system currently may be nearly balanced in terms of the net GWP of these biogenic atmospheric gases. Of course, large uncertainties remain for these estimates, but the papers published here demonstrate tremendous progress, and also large remaining hurdles, in narrowing these uncertainties in our understanding of how Amazônia functions as a regional entity in the Earth system. [ABSTRACT FROM AUTHOR]

Guerreiro, J.S., Ranieri, L. A., El-Robrini, M., Vila-Concejo. Seasonal changes of a dynamic macrotidal beach: Case Study of Marieta beach(Amazon Coast/Brazil) The Amazon Atlantic Coast is a very dynamic area due to the large discharge associated to a large network of rivers that include the Amazon River. Many of the beaches in this area are located within the area of influence of macrotidal range. There is a large sediment availability that creates extensive tidal flats. Waves are moderate with average offshore of 1.8m. The area has a tropical climate with two seasons, rainy and dry, and is under influence of moderate SE/NE trade winds. This paper presents topographic and hydrodynamic data from one of these beaches, Marieta Beach, and shows that while it undergoes severe erosion during the rainy season, accretion and recovery occurs during the dry season. Erosion seems to be associated to the large river discharge in the rainy season (10 3 to 10 4 m3/s−1), high water levels coupled with strong ebbing currents that remove the sediment from the beach. The beach accumulates large volumes of sediment during the dry season (averaging 15.2 m3); the processes that drive sediment transport are not clear but given that onshore winds occur during this period, it is hypothesized that locally wind- generated waves are capable of transporting sediment back to the beach. Seasonal behavior in this case is associated to the tropical seasonality of the rivers instead of traditional storm/fair weather conditions cycles that are often found in the literature. [ABSTRACT FROM AUTHOR]

One of the less studied components of carbon cycling that could improve our understanding of how and how strongly Amazonian ecosystems act as sinks or sources of carbon is the amount that is carried downstream by rivers. In this paper, we show that a headwater river can carry from 25 to 130 % of the reported sink for Amazonian forests, therefore not being negligible for ecosystem-level carbon budgets. Based on monthly measurements from May 2004 to April 2005 of the upper Purus River, southwestern Amazonia, we found that: water pH, dissolved oxygen, specific electrical conductivity, and dissolved inorganic carbon (DIC) were inversely related to water discharge and precipitation; pCO was directly and strongly related to discharge and precipitation, and to a lesser extent to pH and dissolved oxygen; and dissolved organic carbon (DOC) was not related to any measured variable. Annual flux of dissolved carbon (DIC + DOC) at the sampling site was estimated as 604 ± 55 Gg C a. More than 75 % was in the form of bicarbonate, with the remainder as CO and DOC. This amount is equivalent to 0.15 ± 0.01 Mg C ha a in the upstream drainage basin, which is on the same order of magnitude as terrestrial carbon fixation. [ABSTRACT FROM AUTHOR]

The Amazon rain forest may undergo significant change in response to future climate change. To determine the likelihood and causes of such changes, the authors analyzed the output of 24 models from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) and a dynamic vegetation model, Vegetation-Global-Atmosphere-Soil (VEGAS), driven by these climate output. Their results suggest that the core of the Amazon rain forest should remain largely stable because rainfall in the core of the basin is projected to increase in nearly all models. However, the periphery, notably the southern edge of Amazonia and farther south into central Brazil (SAB), is in danger of drying out, driven by two main processes. First, a decline in precipitation of 11%% during the southern Amazonia's dry season (May-September) reduces soil moisture. Two dynamical mechanisms may explain the forecast reduction in dry season rainfall: 1) a general subtropical drying under global warming when the dry season southern Amazon basin is under the control of subtropical high pressure and 2) a stronger north-south tropical Atlantic sea surface temperature gradient and, to a lesser degree, a warmer eastern equatorial Pacific. The drying corresponds to a lengthening of the dry season by approximately 10 days. The decline in soil moisture occurs despite an increase in precipitation during the wet season, because of nonlinear responses in hydrology associated with the decline in dry season precipitation, ecosystem dynamics, and an increase in evaporative demand due to the general warming. In terms of ecosystem response, higher maintenance cost and reduced productivity under warming may also have additional adverse impact. Although the IPCC models have substantial intermodel variation in precipitation change, these latter two hydroecological effects are highly robust because of the general warming simulated by all models. As a result, when forced by these climate projections, a dynamic vegetation model VEGAS projects an enhancement of fire risk by 20%%-30%% in the SAB region. Fire danger reaches its peak in Amazonia during the dry season, and this danger is expected to increase primarily because of the reduction in soil moisture and the decrease in dry season rainfall. VEGAS also projects a reduction of about 0.77 in leaf area index (LAI) over the SAB region. The vegetation response may be partially mediated by the CO2 fertilization effect, because a sensitivity experiment without CO2 fertilization shows a higher 0.89 decrease in LAI. Southern Amazonia is currently under intense human influence as a result of deforestation and land-use change. Should this direct human impact continue at present rates, added pressure to the region's ecosystems from climate change may subject the region to profound changes in the twenty-first century. [ABSTRACT FROM AUTHOR]

Amazonia is one of the world's most vulnerable regions to climate change but few studies pinpointing priority areas for local adaptation programmes exist. This paper aims to identify socio-climatic hotspots among the 515 municipalities that compose the Brazilian Amazon by using a three-step process. First, we identified the regional social hotspots, that is, municipalities that have currently low adaptive capacity, by calculating a composite infrastructure index based on the assessment of both current green and socioeconomic infrastructures. Second, we used a Regional Climate Change Index to identify the climate change hotspots, that is, those municipalities that have a high likelihood to experience future climate change risks. Third, we evaluated the geographic coincidence of social and climate change hotspots to identify the socio-climatic hotspots. We found that 117 municipalities are regional social hotspots and that 60 municipalities are regional climate change hotspots. Forty-six municipalities are considered as socio-climatic hotspots because they have very low to low composite infrastructure indices and very high climate risk indices. Local institutional capacity to integrate and execute national-level policies that enhance local adaptive capacity is a major constraint across the region. To face the challenges associated with climate change, municipalities in the Brazilian Amazon should embrace a more sustainable development model. Sustainable development, in the context of the Brazilian Amazon, implies conservation of the existing green infrastructure through the expansion of protected areas and indigenous lands, restoration of green infrastructure in areas of deficit, and substantial investments in urban socioeconomic infrastructures to foster a knowledge-based economy. Although local sustainable development and adaptation plans are essential across the entire region, the 46 municipalities identified in this study as regional socio-climatic hotspots could be prioritized for action. [ABSTRACT FROM AUTHOR]

The authors simulated the effects of Amazonian mesoscale deforestation in the boundary layer and in rainfall with the Brazilian Regional Atmospheric Modeling System (BRAMS) model. They found that both the area and shape (with respect to wind incidence) of deforestation and the soil moisture status contributed to the state of the atmosphere during the time scale of several weeks, with distinguishable patterns of temperature, humidity, and rainfall. Deforestation resulted in the development of a three-dimensional thermal cell, the so-called deforestation breeze, slightly shifted downwind to large-scale circulation. The boundary layer was warmer and drier above 1000-m height and was slightly wetter up to 2000-m height. Soil wetness affected the circulation energetics proportionally to the soil dryness (for soil wetness below ∼∼0.6). The shape of the deforestation controlled the impact on rainfall. The horizontal strips lined up with the prevailing wind showed a dominant increase in rainfall, significant up to about 60 000 km2. On the other hand, in the patches aligned in the opposite direction (north--south), there was both increase and decrease in precipitation in two distinct regions, as a result of clearly separated upward and downward branches, which caused the precipitation to increase for patches up to 15 000 km2. The authors'' estimates for the size of deforestation impacting the rainfall contributed to fill up the low spatial resolution in other previous studies. [ABSTRACT FROM AUTHOR]

•The rich ecology of tropical forests is intimately tied to their moisture status. Multi-site syntheses can provide a macro-scale view of these linkages and their susceptibility to changing climates. Here, we report pan-tropical and regional-scale analyses of tree vulnerability to drought. •We assembled available data on tropical forest tree stem mortality before, during, and after recent drought events, from 119 monitoring plots in 10 countries concentrated in Amazonia and Borneo. •In most sites, larger trees are disproportionately at risk. At least within Amazonia, low wood density trees are also at greater risk of drought-associated mortality, independent of size. For comparable drought intensities, trees in Borneo are more vulnerable than trees in the Amazon. There is some evidence for lagged impacts of drought, with mortality rates remaining elevated 2 yr after the meteorological event is over. •These findings indicate that repeated droughts would shift the functional composition of tropical forests toward smaller, denser-wooded trees. At very high drought intensities, the linear relationship between tree mortality and moisture stress apparently breaks down, suggesting the existence of moisture stress thresholds beyond which some tropical forests would suffer catastrophic tree mortality. [ABSTRACT FROM AUTHOR]

The Amazon rain forest constitutes one of the major global stocks of carbon. Recent studies, including the last Intergovernmental Panel on Climate Change report and the Coupled Climate Carbon Cycle Model Intercomparison Project, have suggested that it may reduce in size and lose biomass during the twenty-first century through a savannization process. A better understanding of how this ecosystem structure, dynamics, and carbon balance may respond to future climate changes is needed. This article investigates how well a fully coupled atmosphere–biosphere model can reproduce vegetation structure and dynamics in Amazonia to the extent permitted by available data. The accurate representation of the coupled climate–biosphere dynamics requires the accurate representation of climate, net primary production (NPP), and its partition among the several carbon pool components. The simulated climate is validated against precipitation (within 5% of four datasets) and incident solar radiation (within 7% of observations). The authors also validate (i) simulated land cover, which reproduces well the observed patterns; (ii) NPP, within 5% of observations; and (iii) respiration rates, within 15% of observations. The performance of simulated variables that depend on carbon allocation, like NPP partitioning, leaf area index, and aboveground live biomass, although good on a regional mean, is significantly low when spatial patterns are considered. These errors may be attributed to fixed carbon allocation and residence time parameters assumed by the model. Carbon allocation apparently varies spatially, and to simulate this spatial variability is quite a challenge. [ABSTRACT FROM AUTHOR]

This paper describes a severe outbreak of a Lepidopteran defoliator, Lusura altrix (Stoll 1782), on Brazil nut trees in Central Amazonia. The pest outbreak appeared to succeed abnormal weather conditions, and defoliation was sufficient to disrupt normal phenological patterns. [ABSTRACT FROM AUTHOR]

Future global emissions of aerosols will play an important role in governing the nature and magnitude of future anthropogenic climate change. We present in this paper a number of future scenarios of emissions of black carbon (BC) and organic carbon (OC) by world region, which we combine with sulfate (SO4) assessed in terms of the emissions of its precursor, SO2. We find that aerosol emissions from the household and industrial sectors are likely to decline along almost all future pathways. Transportation emissions, however, are subject to complex interacting forces that can lead to either increases or decreases. Biomass burning declines in many scenarios, but the Amazon rainforests remain vulnerable if unsustainable economic growth persists. East Asia is the key region for primary aerosols, and trends in China will have a major bearing on the direction and magnitude of releases of BC (expected reductions in the range of 640--1290 Gg), OC (reductions of 520--1900 Gg), and SO2 (ranging from an increase of 21 Tg to a reduction of 30 Tg). Analysis of joint BC, OC, and SO2 emission changes identifies a number of key world regions and economic sectors that could be effectively targeted for aerosol reductions. [ABSTRACT FROM AUTHOR]

Our aim with this paper is to present a novel approach for developing story lines and scenarios by combining qualitative knowledge and quantitative data from different disciplines and discussing the results with relevant decision makers. This research strategy offers a solid foundation for perspectives into the future. The "laboratory" is the Brazilian Amazon, one of the hotspots of land-use change where local and global interests both collide and converge: local livelihoods are affected by regional and global climate change and by the loss of biodiversity caused by local and global economic interests in agro-industrial land use; such use contributes, in turn, to climate change. After decades of diverse policy interventions the question arises: What can we learn from past trajectories for a more sustainable development in the future? To answer this question, we combined qualitative story lines for the region, reviewed by local experts, with quantitative land-use scenarios, to study their regional and local manifestations in space. These results were then discussed again with local and national experts. Our findings suggest that in-depth knowledge of the diverging perspectives at a very local level is a fundamental prerequisite for downscaling global scenarios and upscaling local approaches to sustainable land-use management and thus, to producing communicable and applicable results. [ABSTRACT FROM AUTHOR]

Climate change threatens many native species from the Amazon Forest. Among the endangered species is the Açaí (Euterpe oleracea), which is a species with great national and international interest, due to the nutritional benefits and medicinal properties of its fruits. However, there is still no information on the ecophysiological responses of Açaí to climate change. Thus, the objective of this work was to evaluate the effect of increased temperature and CO2 concentration change on the ecophysiology of Açaí seedlings. To do so, Açaí seedlings were subjected, for 90 days, to three different climatic scenarios: current Amazon; RCP4.5 (current average temperature in the Amazon + 2.5 °C and 538 ppm of carbon dioxide concentration i.e. CO2); and RCP8.5 (+ 4.5 °C and 936 ppm of CO2 concentration). In addition, two irrigation levels were applied within each climatic scenario: seedlings maintained at 90% (not stressed) and 40% (stressed) of the water holding capacity of the substrate. Gas exchange, water status, fluorescence parameters, enzymatic antioxidants activity and dry matter production were evaluated. High CO2 concentration enhanced Açaí gas exchange (increasing CO2 assimilation), regardless of substrate water availability and temperature. However, high temperature and high vapor-pressure deficit reduced quantum yield and increased the minimum fluorescence and enzymatic antioxidants activity. With that, Açaí seedlings did not convert the additional assimilated carbon (due to higher CO2 concentration) into biomass, showing decreased total dry mass accumulation for RCP4.5 and RCP8.5 climate scenarios. Our results indicated that the positive impacts of increased CO2 concentration to gas exchange may not offset the negative impacts of increased air temperature and VPD to Açaí growth. [ABSTRACT FROM AUTHOR]

This article discusses two distinct notions of harm, wakllichishka and oil harm, and two distinct ways of shaping bodies. Following postcolonial and decolonial insights, I develop an approach that deploys two Indigenous concepts— wakllichishka , and not being able to see the diagnosis —as valid tools of analysis. Kichwa people in northern Peruvian Amazonia use both to analyze the condition of being harmed, illness, and the possibility of recovering. While wakllichishka rests on understandings and practices that assume that bodies are transformable and the locus of human and more-than-human sociality and agency, not being able to see the diagnosis reveals how biomedical and toxicological practices enact bodies as indicators of unspecific conditions and environmental degradation, and as incurable. Using Kichwa analytics shows the situatedness of these practices and counteracts a common disposition to undertake a colonizing reduction that defines our own categories as the only ones adequate for analysis of the consequences of extractive capitalism. [ABSTRACT FROM AUTHOR]

Amazon forests are being degraded by myriad anthropogenic disturbances, altering ecosystem and climate function. We analyzed the effects of a range of land‐use and climate‐change disturbances on fine‐scale canopy structure using a large database of profiling canopy lidar collected from disturbed and mature Amazon forest plots. At most of the disturbed sites, surveys were conducted 10–30 years after disturbance, with many exhibiting signs of recovery. Structural impacts differed in magnitude more than in character among disturbance types, producing a gradient of impacts. Structural changes were highly coordinated in a manner consistent across disturbance types, indicating commonalities in regeneration pathways. At the most severely affected site – burned igapó (seasonally flooded forest) – no signs of canopy regeneration were observed, indicating a sustained alteration of microclimates and consequently greater vulnerability to transitioning to a more open‐canopy, savanna‐like state. Notably, disturbances rarely shifted forests beyond the natural background of structural variation within mature plots, highlighting the similarities between anthropogenic and natural disturbance regimes, and indicating a degree of resilience among Amazon forests. Studying diverse disturbance types within an integrated analytical framework builds capacity to predict the risk of degradation‐driven forest transitions. [ABSTRACT FROM AUTHOR]

Copyright of Revista Derecho del Estado is the property of Universidad Externado de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Brazilian Amazonian Forest is undergoing significant changes in land use and land cover in the last few decades. This land-use transition, besides climate change, may be responsible for the fire regime transition in this territory. Therefore, we aimed at investigating how the fire-transition occurs over time in the Brazilian Amazonia Forest and identifying the key parameters that can help to predict this change. For this, we collected yearly data on fire occurrence, forest cover, deforestation rates, and cropland areas. We used a 0.45° spatial surface grid, and with these annual values, we produced: (i) generalised linear mixed models of fire occurrence against forest cover, using years and grids as random factors; (ii) annual linear models of fire occurrence against forest cover; (iii) linear models of the apex values against the years; and (iv) generalised linear models of these apex values against deforestation and cropland areas. We found that there is a fire-transition process in the Brazilian Amazon Forest since a quadratic model better predicted the fire occurrence behaviour. Moreover, the fire occurrence apex is transitioning to more forested landscapes, from 50.7% in 2003 to 55% in 2019 (R² = 0.3). The deforestation rates and the cropland expansion had important relationships with the fire-transition, the first is related to the fire occurrence in the landscape (R² = 0.62), while the second better predicts the transition to more forested areas (R² = 0.38). Thus, we found that the fire-transition in the Brazilian Amazon Forest is strongly related to the land-use transition stages in this region. [ABSTRACT FROM AUTHOR]

Extreme precipitation and drought events are predicted to become more intense and more frequent over the Amazon rainforest. Because changes in forest dynamics could prompt strong feedback loops to the global climate, it is of crucial importance to gain insight into the response of tropical forests to these recurring extreme climatic events. Here, we evaluated the Amazon forest stability (resistance and resilience) to drought in the context of past dry and wet climatic events using MODIS EVI satellite imagery and cumulative water deficit anomalies. We observed large spatial differences in the occurrence of extreme climatic events from 1980 to 2019, with an increase in drought frequency in the central and northern Amazon and drought intensity in the southern Amazon basin. An increasing trend in the occurrence of wet events was found in the western, southern, and eastern Amazon. Furthermore, we found significant legacy effects of previous climatic events on the forest drought response. An extreme drought closely preceding another drought decreased forest resilience, whereas the occurrence of a recent drier‐than‐usual event also decreased the forest resistance to later droughts. Both wetter‐than‐usual and extreme wet events preceding an extreme drought increased the resistance of the forest, and with similar effects sizes as dry events, indicating that wet and dry events have similarly sized legacy effects on the drought response of tropical forests. Our results indicate that the predicted increase in drought frequency and intensity can have negative consequences for the functioning of the Amazon forest. However, more frequent wet periods in combination with these droughts could counteract their negative impact. Finally, we also found that more stable forests according to the alternative stable states theory are also more resistant and resilient to individual droughts, showing a positive relationship between the equilibrium and non‐equilibrium stability dynamics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Applied Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The future of the Amazon rainforest is a matter of much concern worldwide. It has been predicted that increasing deforestation and the impact of climate change would rapidly and dramatically reduce the extent of the forest area and its density. Some authors have suggested the possibility of a catastrophic savannisation or die-back of the forest in a relatively short time due to global warming and deforestation combined. This die-back in turn would itself contribute to an acceleration of global warming. The Amazon is also involved in debates about energy, including concerns that deforestation adds to C02 emissions and that expanding bio fuel crops and oil gas exploration and extraction further threaten the forest. This paper, which essentially follows the climate projections of the latest (2007) report from the Intergovernmental Panel on Climate Change (IPCC) as well as other available data and scientific results on the prospects of global and regional climate, examines the evidence about deforestation trends and about the expected impact of climate change over the Amazon. It concludes that deforestation rates are much lower than previously thought and rapidly decreasing; that deforestation is largely concentrated along the basin's borders outside the vast rainforest core; and that, even in the absence of the observed declining trends in deforestation, catastrophic forecasts of rapid Amazon die-back' also lack scientific basis, especially when predicted to occur in a few decades or within this century. [ABSTRACT FROM AUTHOR]

Abstract: The ecological consequences of climate change for large tropical forests such as the Amazon are likely to be profound. Amazonian forests strongly influence regional and global climates and therefore any changes in forest structure, such as deforestation or die-back, may create positive feedback on externally forced climate change. Monitoring, modelling and managing the impacts of anthropogenic climate change on forest dynamics is therefore an important objective of forest researchers, and one that requires long-term data on changes at the level of community, populations and phenotypes. In this paper we provide the most comprehensive study yet on the seasonal dynamics of various leaf traits: leaf area index (LAI), leaf mortality (LM), leaf biomass (LB), leaf growth rate (LG), and leaf residence time (TR) from 50 experimental plots in a forest site at Belterra, Pará State, Brazil. From this study we estimate annual mean leaf area index (LAI) to be 5.07m2 m−2 and annual mean leaf dry biomass to be 0.621kgm−2. The typical leaf grew at 0.049kgm−2 month−1 and remained on the tree for 12.7 months. We compare these results to other similar studies and critically discuss the factors driving leaf demographics in Amazonia. [Copyright &y& Elsevier]

In this paper, we review some critical issues regarding carbon cycling in Amazonia, as revealed by several studies conducted in the Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA). We evaluate both the contribution of this magnificent biome for the global net primary productivity/net ecosystem exchange (NPP/NEE) and the feedbacks of climate change on the dynamics of Amazonia. In order to place Amazonia in a global perspective and make the carbon flux obtained through the LBA project comparable with global carbon budgets, we extrapolated NPP/NEE values found by LBA studies to the entire area of the Brazilian Amazon covered by rainforest. The carbon emissions due to land use changes for the tropical regions of the world produced values from 0.96 to 2.4 Pg C year−1, while atmospheric CO2 inversion models have recently indicated that tropical lands in the Americas could be exchanging a net 0.62±1.15 Pg C year−1 with the atmosphere. The difference calculated from these two methods would imply a local sink of approximately 1.6–1.7 Pg C year−1, or a source of 0.85 ton C ha−1 year−1. Using our crude extrapolation of LBA values for the Amazon forests (5 million km2) we estimate a range for the C flux in the region of −3.0 to 0.75 Pg C year−1. The exercise here does not account for environmental variability across the region, but it is an important driver for present and future studies linking local process (i.e. nutrient availability, photosynthetic capacity, and so forth) to global and regional dynamic approaches. [ABSTRACT FROM AUTHOR]

The climate change endangers many species of the Amazon Forest. An example, in the endangered medicinal species Pilocarpus microphyllus (popularly known as jaborandi). The jaborandi is a natural source of alkaloids used for serious diseases, essential for medical use. However, the potential impacts of climate change on this species are still unknown. Thus, the objective was to evaluate the effect of high temperature and high atmospheric concentrations of CO2, projected to occur with climate change, combined with water stress, on the ecophysiology of jaborandi seedlings. For this, seedlings were exposed to three different climatic scenarios in a controlled environment, characterized as current Amazon: RCP4.5 (current Amazon average temperature + 2.5 °C and 538 ppm of [CO2]) and RCP 8.5 (+ 4.5 °C and 936 ppm of [CO2]). Within each climatic scenario, two levels of irrigation were applied: 90% (well-watered) and 40% (water-stressed) of the substrate water holding capacity. Growth variables, plant water status, fluorescence parameters, and enzymatic antioxidants activity were evaluated. The results showed that the jaborandi seedlings showed greater total dry mass production when grown in the current Amazon with no water stress. The seedlings' growth was negatively affected by the scenarios enriched with CO2, especially RCP 8.5. Climate change scenarios had the greatest negative impact when the seedlings were subject to water stress. Under these scenarios of climate change and water stress, the seedlings allocated more carbohydrates to the root system. The negative effect of water stress on jaborandi physiology and growth was attenuated by the RCP 8.5 scenario. Our results indicated that the predicted climate changes negatively impact ecophysiology jaborandi, being a threat to the extinction of this species. [ABSTRACT FROM AUTHOR]

This paper describes four global-change phenomena that are having major impacts on Amazonian forests. The first is accelerating deforestation and logging. Despite recent government initiatives to slow forest loss, deforestation rates in Brazilian Amazonia have increased from 1.1 million ha yr-1 in the early 1990s, to nearly 1.5 million ha yr-1 from 1992–1994, and to more than 1.9 million ha yr-1 from 1995–1998. Deforestation is also occurring rapidly in some other parts of the Amazon Basin, such as in Bolivia and Ecuador, while industrialized logging is increasing dramatically in the Guianas and central Amazonia. The second phenomenon is that patterns of forest loss and fragmentation are rapidly changing. In recent decades, large-scale deforestation has mainly occurred in the southern and eastern portions of the Amazon — in the Brazilian states of Pará, Maranhāo, Rondônia, Acre, and Mato Grosso, and in northern Bolivia. While rates of forest loss remain very high in these areas, the development of major new highways is providing direct conduits into the heart of the Amazon. If future trends follow past patterns, land-hungry settlers and loggers may largely bisect the forests of the Amazon Basin. The third phenomenon is that climatic variability is interacting with human land uses, creating additional impacts on forest ecosystems. The 1997/98 El Niño drought, for example, led to a major increase in forest burning, with wildfires raging out of control in the northern Amazonian state of Roraima and other locations. Logging operations, which create labyrinths of roads and tracks in forsts, are increasing fuel loads, desiccation and ignition sources in forest interiors. Forest fragmentation also increases fire susceptibility by creating dry, fire-prone forest edges. Finally, recent evidence suggests that intact Amazonian forests are a globally significant carbon sink, quite possibly caused by higher forest growth rates in response to increasing atmospheric CO2 fertilization. Evidence for a carbon sink comes from long-term forest mensuration plots, from whole-forest studies of carbon flux and from investigations of atmospheric CO2 and oxygen isotopes. Unfortunately, intact Amazonian forests are rapidly diminishing. Hence, not only is the destruction of these forests a major source of greenhouse gases, but it is reducing their intrinsic capacity to help buffer the rapid anthropogenic rise in CO2. [ABSTRACT FROM AUTHOR]

The article focuses on crucial role of primary forests, such as the Amazon, in climate change mitigation that is recognized in the scientific literature. Topics include considered that Amazon fires of 2019 have heightened attention on the region and brought the question of Amazon conservation to the forefront of international debate.

Tropical forests are experiencing unprecedented high‐temperature conditions due to climate change that could limit their photosynthetic functions. We studied the high‐temperature sensitivity of photosynthesis in a rainforest site in southern Amazonia, where some of the highest temperatures and most rapid warming in the Tropics have been recorded. The quantum yield (Fv/Fm) of photosystem II was measured in seven dominant tree species using leaf discs exposed to varying levels of heat stress. T50 was calculated as the temperature at which Fv/Fm was half the maximum value. T5 is defined as the breakpoint temperature, at which Fv/Fm decline was initiated. Leaf thermotolerance in the rapidly warming southern Amazonia was the highest recorded for forest tree species globally. T50 and T5 varied between species, with one mid‐storey species, Amaioua guianensis, exhibiting particularly high T50 and T5 values. While the T50 values of the species sampled were several degrees above the maximum air temperatures experienced in southern Amazonia, the T5 values of several species are now exceeded under present‐day maximum air temperatures. Although high‐temperature tolerance of photosystem II (PSII) in trees from the southern Amazonian forests was the highest in the literature, maximum air temperatures during the dry periods has already reached levels that overlap with the range of PSII temperature sensitivity. [ABSTRACT FROM AUTHOR]

The Amazon Rainforest is facing high rates of deforestation, leaving anthropogenically dominated landscapes across the Amazon. Understanding the biodiversity response to the effects of rainfall seasonality can provide important examples of how species may respond to drastic climate conditions in anthropogenic landscapes. Here, we sampled dung beetles across the same Amazon forest sites during the rainy and dry seasons to evaluate the effect of seasonality on biodiversity patterns. We found a significant space–time interaction for the whole set of forest sites indicating that the spatial structure of the species abundance data has changed significantly between seasons. Dung beetle abundance and species richness was higher in the rainy season when evaluating all species and separately for nesting behavior group. For presence-absence and abundance data of the whole assemblage, the mean differences between losses and gains over all forest sites was negative, indicating dominance of species and individuals-per-species losses across all forest sites. Eleven species (5 tunnellers, 4 rollers, and 2 dwellers) had significant decreases in abundances in the forest sites from the rainy to the dry season, whereas one roller species increased in abundance from the rainy to the dry season. Rainfall seasonality drives the temporal patterns of dung beetle diversity in the Amazonian forests in the study region in the arc of deforestation. Implications for insect conservation: Understanding species vulnerability to changes in climatic conditions could help to predict species distributions in an increased scenario of higher temperatures and longer drought periods during dry seasons in the near future. [ABSTRACT FROM AUTHOR]

In the Amazon rainforest, land use following deforestation is diverse and dynamic. Mounting evidence indicates that the climatic impacts of forest loss can also vary considerably, depending on specific features of the affected areas. The size of the deforested patches, for instance, was shown to modulate the characteristics of local climatic impacts. Nonetheless, the influence of different types of land use and management strategies on the magnitude of local climatic changes remains uncertain. Here, we evaluated the impacts of large-scale commodity farming and rural settlements on surface temperature, rainfall patterns, and energy fluxes. Our results reveal that changes in land-atmosphere coupling are induced not only by deforestation size but also, by land use type and management patterns inside the deforested areas. We provide evidence that, in comparison with rural settlements, deforestation caused by large-scale commodity agriculture is more likely to reduce convective rainfall and increase land surface temperature. We demonstrate that these differences are mainly caused by a more intensive management of the land, resulting in significantly lower vegetation cover throughout the year, which reduces latent heat flux. Our findings indicate an urgent need for alternative agricultural practices, as well as forest restoration, for maintaining ecosystem processes and mitigating change in the local climates across the Amazon basin. [ABSTRACT FROM AUTHOR]

The Andean-Amazon foothills region, shaped by Andean moist forests and Amazon forests in southwestern Colombia, Napo province in Ecuador, and Ucayali Province and Napo Basin in Peru, provides local and global ecosystem services as food, water, world climate regulation, water purification, and carbon absorption. However, it faces major problems of land-use change that are exacerbated by climate change that affects these ecosystem services. For instance, conventional agriculture contribute to deforestation, soil degradation, and biodiversity loss, which might be further aggravated by climate change–induced droughts, thus reducing staple crop production and, consequently, food security. Cassava (Manihot esculenta Crantz), maize (Zea mays L.), and plantain (Musa paradisiaca L.) are major staple crops in the region. They play a key role for food security and local farmers' income but are highly exposed to climate risks. This article aims to quantify the level of exposure to climate change (measured as climatic suitability) of these crops in the Andean-Amazon foothills by using the EcoCrop model by the 2030s, 2050s, and 2080s under Representative Concentration Pathway 2.6, 4.5, and 8.5 scenarios. EcoCrop results showed that, whereas cassava will not lose climatic suitability, maize will lose more than half of its current suitable area, and plantain will gain and lose area, which would affect local food security. Globally, these results are important in highlighting adaptive and cost-effective strategies in agriculture and suggest that agricultural crop diversification may improve resilience by promoting the use of local crops varieties. [ABSTRACT FROM AUTHOR]

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Climate change will redistribute the global biodiversity in the Anthropocene. As climates change, species might move from one place to another, due to local extinctions and colonization of new environments. However, the existence of permeable migratory routes precedes faunal migrations in fragmented landscapes. Here, we investigate how dispersal will affect the outcome of climate change on the distribution of Amazon's primate species. We modeled the distribution of 80 Amazon primate species, using ecological niche models, and projected their potential distribution on scenarios of climate change. Then, we imposed landscape restrictions to primate dispersal, derived from a natural biogeographical barrier to primates (the main tributaries of the Amazon river) and an anthropogenic constraint to the migration of many canopy‐dependent animals (deforested areas). We also highlighted potential conflict zones, i.e. regions of high migration potential but predicted to be deforested. Species response to climate change varied across dispersal limitation scenarios. If species could occupy all newly suitable climate, almost 70% of species could expand ranges. Including dispersal barriers (natural and anthropogenic), however, led to range expansion in only less than 20% of the studied species. When species were not allowed to migrate, all of them lost an average of 90% of the suitable area, suggesting that climate may become unsuitable within their present distributions. All Amazon primate species may need to move as climate changes to avoid deleterious effects of exposure to non‐analog climates. The effect of climate change on the distribution of Amazon primates will ultimately depend on whether landscape permeability will allow climate‐driven faunal migrations. The network of protected areas in the Amazon could work as 'stepping stones' but most are outside important migratory routes. Therefore, protecting important dispersal corridors is foremost to allow effective migrations of the Amazon fauna in face of climate change and deforestation. [ABSTRACT FROM AUTHOR]

Wildfires are increasingly affecting forest landscapes around the world. In the Bolivian Chiquitania, southern Amazonia, large wildfires during recent droughts have intensified public debate around more systemic solutions to address the possible root causes. While the integration of different forms of fire knowledge is gaining acceptance as an approach to dealing with increasing wildfire risk, little attention has been given to this integration in the Amazonia. In fact, mismatches between policy, science and local realities have curtailed the success of fire risk strategies in the region. To address this challenge, we conducted interviews and focus group discussions with a wide range of actors in the Chiquitania to examine different forms of knowledge and views of fire, and the extent to which these were integrated in prevalent wildfire risk strategies. We found that the risk strategies were in tension between two conflicting understandings of fire. A conceptual framework was developed to capture the configuration of knowledge underpinning this tension. Adopting a more integrated and inclusive approach to manage wildfire risk will require overcoming first this tension through a more open deliberation process within a reflexive governance framework. We proposed three "deliberation arenas" to facilitate this process, which could ultimately support more systemic, inter‐cultural fire management in the Chiquitania and other landscapes with conflicting views in the Amazonia. [ABSTRACT FROM AUTHOR]

Abstract: Brazil is one of the major contributors to land‐use change emissions, mostly driven by agricultural expansion for food, feed, and bioenergy feedstock. Policies to avoid deforestation related to private commitments, economic incentives, and other support schemes are expected to improve the effectiveness of current command and control mechanisms increasingly. However, until recently, land tenure was unknown for much of the Brazilian territory, which has undermined the governance of native vegetation and challenged support and incentive mechanisms for avoiding deforestation. We assess the total extent of public governance mechanisms protecting aboveground carbon (AGC) stocks. We constructed a land tenure dataset for the entire nation and modeled the effects and uncertainties of major land‐use acts on protecting AGC stocks. Roughly 70% of the AGC stock in Brazil is estimated to be under legal protection, and an additional 20% is expected to be protected after areas in the Amazon with currently undesignated land undergo a tenure regularization. About 30% of the AGC stock is on private land, of which roughly two‐thirds are protected. The Cerrado, Amazon, and Caatinga biomes hold about 40%, 30%, and 20% of the unprotected AGC, respectively. Effective conservation of protected and unprotected carbon will depend on successful implementation of the Forest Act, and regularization of land tenure in the Amazon. Policy development that prioritizes unprotected AGC stocks is warranted to promote conservation of native vegetation beyond the legal requirements. However, different biomes and land tenure structures may require different policy settings considering local and regional specifics. Finally, the fate of current AGC stocks relies upon effective implementation of command and control mechanisms, considering that unprotected AGC in native vegetation on private land only accounts for 6.5% of the total AGC stock. [ABSTRACT FROM AUTHOR]

The humid forests of Amazonia are experiencing longer and more intense dry seasons, which are predicted to intensify by the end of the 21st century. Although tree species often have long generation times, they may still have the capacity to rapidly respond to changing climatic conditions through adaptive phenotypic plasticity. We, therefore, predicted that Amazonian trees have shifted their leaf morphology in response to the recent drier climate. We tested this prediction by analysing historical herbarium specimens of six Amazonian tree species collected over a 60-year period and comparing changes in leaf morphology with historical precipitation data. Moreover, we explored spatial and temporal biases in herbarium specimens and accounted for their potentially confounding effect in our analysis. We found pronounced biases in herbarium specimens, with nearly 20% of specimens collected in close geographic proximity and around the 1975s. When accounting for such biases, our results indicate a trend of decreasing leaf size after the 1970s, which may have been spurred by an observed reduction in rainfall. Our findings support the hypothesis that (some) Amazonian trees have the capacity to adaptively change their leaf phenotypes in response to the recent drier climate. Nevertheless, the unavoidable spatial and temporal biases in herbarium specimens call for caution when generalizing our findings to all Amazonian trees. [ABSTRACT FROM AUTHOR]

Tropical second-growth forests could help mitigate climate change, but the degree to which their carbon potential is achieved will depend on exposure to disturbance. Wind disturbance is common in tropical forests, shaping structure, composition, and function, and influencing successional trajectories. However, little is known about the impacts of extreme winds on second-growth forests in fragmented landscapes, though these ecosystems are often located in mosaics of forest, pasture, cropland, and other land cover types. Indirect evidence suggests that fragmentation increases risk of wind damage in tropical forests, but no studies have found such impacts following severe storms. In this study, we ask whether fragmentation and forest type (old vs. second growth) were associated with variation in wind damage after a severe convective storm in a fragmented production landscape in western Amazonia. We applied linear spectral unmixing to Landsat 8 imagery from before and after the storm, and combined it with field observations of damage to map wind effects on forest structure and biomass. We also used Landsat 8 imagery to map land cover with the goals of identifying old- and second-growth forest and characterizing fragmentation. We used these data to assess variation in wind disturbance across 95,596 ha of forest, distributed over 6,110 patches. We find that fragmentation is significantly associated with wind damage, with damage severity higher at forest edges and in edgier, more isolated patches. Damage was also more severe in old-growth than in second-growth forests, but this effect was weaker than that of fragmentation. These results illustrate the importance of considering landscape context in planning tropical forest restoration and natural regeneration projects. Assessments of long-term carbon sequestration potential need to consider spatial variation in disturbance exposure. Where risk of extreme winds is high, minimizing fragmentation and isolation could increase carbon sequestration potential. [ABSTRACT FROM AUTHOR]

The Amazon rainforest is disproportionately important for global carbon storage and biodiversity. The system couples the atmosphere and land, with moist forest that depends on convection to sustain gross primary productivity and growth. Earth system models that estimate future climate and vegetation show little agreement in Amazon simulations. Here we show that biases in internally generated climate, primarily precipitation, explain most of the uncertainty in Earth system model results; models, empirical data and theory converge when precipitation biases are accounted for. Gross primary productivity, above-ground biomass and tree cover align on a hydrological relationship with a breakpoint at ~2000mm annual precipitation, where the system transitions between water and radiation limitation of evapotranspiration. The breakpoint appears to be fairly stable in the future, suggesting resilience of the Amazon to climate change. Changes in precipitation and land use are therefore more likely to govern biomass and vegetation structure in Amazonia. [ABSTRACT FROM AUTHOR]

For half a century, the process of economic integration of the Amazon has been based on intensive use of renewable and nonrenewable natural resources, which has brought significant basin-wide environmental alterations. The rural development in the Amazonia pushed the agricultural frontier swiftly, resulting in widespread land-cover change, but agriculture in the Amazon has been of low productivity and unsustainable. The loss of biodiversity and continued deforestation will lead to high risks of irreversible change of its tropical forests. It has been established by modeling studies that the Amazon may have two "tipping points," namely, temperature increase of 4 °C or deforestation exceeding 40% of the forest area. If transgressed, large-scale "savannization" of mostly southern and eastern Amazon may take place. The region has warmed about 1 °C over the last 60 y, and total deforestation is reaching 20% of the forested area. The recent significant reductions in deforestation--80% reduction in the Brazilian Amazon in the last decade--opens up opportunities for a novel sustainable development paradigm for the future of the Amazon. We argue for a new development paradigm--away from only attempting to reconcile maximizing conservation versus intensification of traditional agriculture and expansion of hydropower capacity--in which we research, develop, and scale a high-tech innovation approach that sees the Amazon as a global public good of biological assets that can enable the creation of innovative high-value products, services, and platforms through combining advanced digital, biological, and material technologies of the Fourth Industrial Revolution in progress. [ABSTRACT FROM AUTHOR]

Future intensification of Amazon drought resulting from climate change may cause increased fire activity, tree mortality, and emissions of carbon to the atmosphere across large areas of Amazonia. To provide a basis for addressing these issues, we examine properties of recent and future meteorological droughts in the Amazon in 35 climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We find that the CMIP5 climate models, as a group, simulate important properties of historical meteorological droughts in the Amazon. In addition, this group of models reproduces observed relationships between Amazon precipitation and regional sea surface temperature anomalies in the tropical Pacific and the North Atlantic oceans. Assuming the Representative Concentration Pathway 8.5 scenario for future drivers of climate change, the models project increases in the frequency and geographic extent of meteorological drought in the eastern Amazon, and the opposite in the West. For the region as a whole, the CMIP5 models suggest that the area affected by mild and severe meteorological drought will nearly double and triple, respectively, by 2100. Extremes of wetness are also projected to increase after 2040. Specifically, the frequency of periods of unusual wetness and the area affected by unusual wetness are projected to increase after 2040 in the Amazon as a whole, including in locations where annual mean precipitation is projected to decrease. Our analyses suggest that continued emissions of greenhouse gases will increase the likelihood of extreme events that have been shown to alter and degrade Amazonian forests. [ABSTRACT FROM AUTHOR]

The exchanges of carbon, water and energy between the atmosphere and the Amazon basin have global implications for the current and future climate. Here, the global atmospheric inversion system of the Monitoring of Atmospheric Composition and Climate (MACC) service is used to study the seasonal and interannual variations of biogenic CO2 fluxes in Amazonia during the period 2002-2010. The system assimilated surface measurements of atmospheric CO2 mole fractions made at more than 100 sites over the globe into an atmospheric transport model. The present study adds measurements from four surface stations located in tropical South America, a region poorly covered by CO2 observations. The estimates of net ecosystem exchange (NEE) optimized by the inversion are compared to an independent estimate of NEE upscaled from eddy-covariance flux measurements in Amazonia. They are also qualitatively evaluated against reports on the seasonal and interannual variations of the land sink in South America from the scientific literature. We attempt at assessing the impact on NEE of the strong droughts in 2005 and 2010 (due to severe and longer-thanusual dry seasons) and the extreme rainfall conditions registered in 2009. The spatial variations of the seasonal and interannual variability of optimized NEE are also investigated. While the inversion supports the assumption of strong spatial heterogeneity of these variations, the results reveal critical limitations of the coarse-resolution transport model, the surface observation network in South America during the recent years and the present knowledge of modelling uncertainties in South America that prevent our inversion from capturing the seasonal patterns of fluxes across Amazonia. However, some patterns from the inversion seem consistent with the anomaly of moisture conditions in 2009. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Reconstruction of Highway BR-319 (Manaus-Porto Velho) would allow for access from the 'arc of deforestation' in the southern part of Brazil's Amazon region to vast blocks of forests in central and northern Amazonia. Building roads is known to be a major driver of deforestation, allowing entry of squatters, and other actors. Rather than deforestation along the highway route, here we consider the road's potential for stimulating deforestation in a separate location, approximately 550 km north of BR-319's endpoint in Manaus. Reconstructing BR-319 has great potential impact to start a new wave of migration to this remote region. The southern portion of the state of Roraima, the focus of our study, is already connected to Manaus by Highway BR-174. We modeled deforestation in southern Roraima and simulated carbon emissions between 2007 and 2030 under four scenarios. Simulations used the AGROECO model in DINAMICA-EGO © software. Two scenarios were considered with reconstruction of BR-319 and two without this road connection. For each of the two possibilities regarding BR-319, simulations were developed for (1) a 'conservation' (CONSERV) scenario that assumes the creation of a series of protected areas, and (2) a 'business-as-usual' (BAU) scenario that assumes no additional protected areas. Results show that by 2030, with BR-319 rebuilt, deforestation carbon emissions would increase between 19 % (CONSERV) and 42 % (BAU) over and above those corresponding to no-road scenarios. [ABSTRACT FROM AUTHOR]

The number of species is known to decrease from the humid tropics towards drier and colder climates, but how species richness varies along environmental and spatial gradients within the tropical rain forests is not clear. We inventoried 214 transects of 0.25 ha to document species diversity patterns in an example plant group (ferns and lycophytes) across non-inundated rain forests of western and central Amazonia, and assessed how well these conformed with proposed hypotheses about species richness. The observed number of species varied between 6 and 71 per transect. The effective number of species (emphasising the degree of unevenness in species abundances) varied between 1.02 and 8.60, and diversity profiles revealed considerable differences among transects in community structure. Although the density of individuals varied over almost two orders of magnitude, species diversity was better explained by other variables. In particular, within-transect species diversity increased substantially with increasing soil cation concentration. It also increased with soil aluminium concentration, heterogeneity in soil chemistry, annual rainfall and dry season rainfall, and was higher in western than in central Amazonia. Multiple regression models explained up to 70% of the variance in species diversity, but the relationships between species diversity and the environmental gradients became progressively weaker as species abundances were given more weight in the calculation of diversity. Our results conformed to the proposal that site productivity promotes species diversity. This seemed to arise from larger species pools on more fertile soils and in wetter climates, even when it could be expected that the older and more widespread infertile soils would have provided more opportunities for speciation. [ABSTRACT FROM AUTHOR]

The carbon and water cycles for a southwestern Amazonian forest site were investigated using the longest time series of fluxes of CO2 and water vapor ever reported for this site. The period from 2004 to 2010 included two severe droughts (2005 and 2010) and a flooding year (2009). The effects of such climate extremes were detected in annual sums of fluxes as well as in other components of the carbon and water cycles, such as gross primary production and water use efficiency. Gap-filling and flux-partitioning were applied in order to fill gaps due to missing data, and errors analysis made it possible to infer the uncertainty on the carbon balance. Overall, the site was found to have a net carbon uptake of ≈5 t C ha−1 year−1, but the effects of the drought of 2005 were still noticed in 2006, when the climate disturbance caused the site to become a net source of carbon to the atmosphere. Different regions of the Amazon forest might respond differently to climate extremes due to differences in dry season length, annual precipitation, species compositions, albedo and soil type. Longer time series of fluxes measured over several locations are required to better characterize the effects of climate anomalies on the carbon and water balances for the whole Amazon region. Such valuable datasets can also be used to calibrate biogeochemical models and infer on future scenarios of the Amazon forest carbon balance under the influence of climate change. [ABSTRACT FROM AUTHOR]

Background:The forests of western Amazonia are known to be more dynamic that the better-studied forests of eastern Amazonia, but there has been no comprehensive description of the carbon cycle of a western Amazonian forest. Aims:We present the carbon budget of two forest plots in Tambopata in south-eastern Peru, western Amazonia. In particular, we present, for the first time, the seasonal variation in the detailed carbon budget of a tropical forest. Methods:We measured the major components of net primary production (NPP) and total autotrophic respiration over 3–6 years. Results:The NPP for the two plots was 15.1 ± 0.8 and 14.2 ± 1.0 Mg C ha−1year−1, the gross primary productivity (GPP) was 35.5 ± 3.6 and 34.5 ± 3.5 Mg C ha−1year−1, and the carbon use efficiency (CUE) was 0.42 ± 0.05 and 0.41 ± 0.05. NPP and CUE showed a large degree of seasonality. Conclusions:The two plots were similar in carbon cycling characteristics despite the different soils, the most notable difference being high allocation of NPP to canopy and low allocation to fine roots in the Holocene floodplain plot. The timing of the minima in the wet–dry transition suggests they are driven by phenological rhythms rather than being driven directly by water stress. When compared with results from forests on infertile forests in humid lowland eastern Amazonia, the plots have slightly higher GPP, but similar patterns of CUE and carbon allocation. [ABSTRACT FROM PUBLISHER]

Background:There is much interest in how the Amazon rainforest may respond to future rainfall reduction. However, there are relatively few ecosystem-scale studies to inform this debate. Aims:We described the carbon cycle in a 1 ha rainforest plot subjected to 8–10 consecutive years of ca. 50% through-fall reduction (TFR) and compare these results with those from a nearby, unmodified control plot in eastern Amazonia. Methods:We quantified the components of net primary productivity (NPP), autotrophic (Ra) and heterotrophic respiration, and estimate gross primary productivity (GPP, the sum ofNPPandRa) and carbon-use efficiency (CUE, the ratio ofNPP/GPP). Results:The TFR forest exhibited slightly lowerNPPbut slightly higherRa, such that forestCUEwas 0.29 ± 0.04 on the control plot but 0.25 ± 0.03 on the TFR plot. Compared with four years earlier, TFR plot leaf area index and small tree growth recovered and soil heterotrophic respiration had risen. Conclusions:This analysis tested and extended the key findings of a similar analysis 4 years earlier in the TFR treatment. The results indicated that, while the forest recovered from extended drought in some respects, it maintained higher overallRarelative to the undroughted control, potentially causing the droughted forest to act as a net source of CO2. [ABSTRACT FROM PUBLISHER]