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Amazonian deforestation is causing notable changes in the hydrological cycle by altering important precipitation characteristics. This study uses daily rainfall time series data from 112 rain gauges and a recent yearly 1‐km land use data set covering the period from 1974 to 2012 to evaluate the effects of the extent of deforestation at different spatial scales on the onset of the rainy season and on the duration of dry spells in southern Amazonia. Correlation analyses indicate a delay in the onset of 0.12–0.17 days per percent increase in deforestation. Analysis of cumulative probability density functions emphasizes that the likelihood of rainy season onset occurring earlier than normal decreases as the local deforestation fraction increases. In addition, the probability of occurrence of dry spells in the early and late rainy season is higher in areas with greater deforestation. The delayed onset and longer dry spell events in highly deforested areas increase the climate risk to agriculture in the region. Key Points: The likelihood of rainy season onset occurring earlier than normal decreases as the local deforestation fraction increasesThe probability of occurrence of dry spells of any duration in this region is higher in areas with greater deforestationThe delayed rainy season onset and longer dry spell events increase the climate risk to agriculture in the region [ABSTRACT FROM AUTHOR]

The SITE® model was originally developed to study the response of tropical ecosystems to varying environmental conditions. The present study evaluated the applicability of the SITE model to simulation of energy fluxes in a tropical semi-deciduous forest of the southern Amazon Basin. The model was simulated with data representing the wet and dry season, and was calibrated according to each season. The output data of the calibrated model [net radiation (Rn), latent heat flux (LE) and sensible heat flux (H)] were compared with data observed in the field for validation. Considering changes in parameter calibration for a time step simulation of 30 min, the magnitude of variation in temporal flux was satisfactory when compared to observation field data. There was a tendency to underestimate and overestimate LE and H, respectively. Of all the calibration parameters, the soil moisture parameter presented the highest variation over the seasons, thus influencing SITE model performance. [ABSTRACT FROM AUTHOR]

The article discusses the role of Cerrado conversation as an essential factor to protect the Amazon rainforest. It provides an overview of the greatest threat to Amazonia such as the conversion to agriculture and climate change. Moreover, it also discusses the regional impacts of deforestation, the implications for conservation of Amazonia and Cerrado and the link between deforestation and climate.

The article presents a study which examines the impact of deforestation scenarios in Amazon and Central Brazil on the period of dry season in the arc-of-deforestation in the region. The study uses simulations for four deforestation scenarios in Amazon and Cerrado to determine the difference of deforestation on regional climate. The results show that deforestation reduces rainforest precipitation in Amazon, and does not cause decrease in rainfall in the rainforest area of Cerrado.

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]

The Amazon Basin is one of the world's most important bioregions, harboring a rich array of plant and animal species and offering a wealth of goods and services to society. For years, ecological science has shown how largescale forest clearings cause declines in biodiversity and the availability of forest products. Yet some important changes in the rainforests, and in the ecosystem services they provide, have been underappreciated until recently. Emerging research indicates that land use in the Amazon goes far beyond clearing large areas of forest; selective logging and other canopy damage is much more pervasive than once believed. Deforestation causes collateral damage to the surrounding forests - through enhanced drying of the forest floor, increased frequency of fires, and lowered productivity. The loss of healthy forests can degrade key ecosystem services, such as carbon storage in biomass and soils, the regulation of water balance and river flow, the modulation of regional climate patterns, and the amelioration of infectious diseases. We review these newly revealed changes in the Amazon rainforests and the ecosystem services that they provide. [ABSTRACT FROM AUTHOR]

It is generally expected that the Amazon basin will experience at least two major environmental changes during the next few decades and centuries: 1) increasing areas of forest will be converted to pasture and cropland, and 2) concentrations of atmospheric CO2 will continue to rise. In this study, the authors use the National Center for Atmospheric Research GENESIS atmospheric general circulation model, coupled to the Integrated Biosphere Simulator, to determine the combined effects of large-scale deforestation and increased CO2 concentrations (including both physiological and radiative effects) on Amazonian climate. In these simulations, deforestation decreases basin-average precipitation by 0.73 mm day 21 over the basin, as a consequence of the general reduction in vertical motion above the deforested area (although there are some small regions with increased vertical motion). The overall effect of doubled CO2 concentrations in Amazonia is an increase in basin-average precipitation of 0.28 mm day 21 . The combined effect of deforestation and doubled CO2 , including the interactions among the processes, is a decrease in the basin-average precipitation of 0.42 mm day 21 . While the effects of deforestation and increasing CO2 concentrations on precipitation tend to counteract one another, both processes work to warm the Amazon basin. The effect of deforestation and increasing CO2 concentrations both tend to increase surface temperature, mainly because of decreases in evapotranspiration and the radiative effect of CO2 . The combined effect of deforestation and doubled CO2 , including the interactions among the processes, increases the basin-average temperature by roughly 3.5°C. [ABSTRACT FROM AUTHOR]

Abstract: The LBA data-model intercomparison project (LBA-DMIP) was designed to compare land surface/ecosystem model simulations of terrestrial energy, water and CO2 fluxes with long-term observations of these quantities over Amazonia to provide understanding on how well these models quantify the land surface process, to assess deficiencies in the models and to suggest how they could be improved. [Copyright &y& Elsevier]

Highlights: [•] Eight observational sites in Amazon were standardized for land surface modeling purposes. [•] A model intercomparison was conducted over the Amazon for understanding of energy, water and carbon exchanges across different tropical ecosystems. [•] Twenty-one parameterizations that model vegetation dynamics, carbon fluxes, energy and water were performed over the Brazilian Amazon. [ABSTRACT FROM AUTHOR]