Publicações

The influence of social context in animal signals can lead to complex communicational patterns. In particular, the interaction between individuals can lead to intriguing collective dynamics, such as the temporal synchronization of signals. A fascinating example of such temporal synchronization involves the waving displays of fiddler crabs, in which males raise and lower their enlarged claws in species-specific rhythms. The adaptive significance of this phenomenon is still obscure, but possibly involves female preference for leading waving displays. However, waving displays are highly complex social signals that might be involved in a variety of forms of communication other than simply attracting females, but little is known about the influence of social context on wave synchronization. In this study we carried out field experiments to investigate the effect of two social factors, male density and female presence, on the level of waving synchronization in the fiddler crab Uca leptodactyla. Groups of males at varying densities were established in enclosures and recorded either in the presence or absence of a female. Our results indicate that the main factor driving synchronization is the presence of the female, with males not only changing the timing of their waving displays, but also altering their spatial distribution in the arenas. On the other hand, male density had a negligible effect on synchronization (despite significantly increasing waving rate), suggesting that malemale communication plays a minor role in the emergence of waving synchronization in this species.

Climate change and biodiversity loss have been reported as major disturbances in the biosphere which can trigger changes in the structure and functioning of natural ecosystems. Nonetheless, empirical studies demonstrating how both factors interact to affect shifts in aquatic ecosystems are still unexplored. Here, we experimentally test how changes in rainfall distribution and litter diversity affect the occurrence of the algae-dominated condition in tank bromeliad ecosystems. Tank bromeliads are miniature aquatic ecosystems shaped by the rainwater and allochthonous detritus accumulated in the bases of their leaves. Here, we demonstrated that changes in the rainfall distribution were able to reduce the chlorophyll-a concentration in the water of bromeliad tanks affecting significantly the occurrence of algaedominated conditions. On the other hand, litter diversity did not affect the algae dominance irrespective to the rainfall scenario. We suggest that rainfall changes may compromise important self-reinforcing mechanisms responsible for maintaining high levels of algae on tank bromeliads ecosystems. We summarized these results into a theoretical model which suggests that tank bromeliads may show two different regimes, determined by the bromeliad ability in taking up nutrients from the water and by the total amount of light entering the tank. We concluded that predicted climate changes might promote regime shifts in tropical aquatic ecosystems by shaping their structure and the relative importance of other regulating factors.

Tropical rainforest plays an important role in the global carbon cycle, accounting for a large part of global net primary productivity and contributing to CO2 sequestration. The objective of this work is to simulate potential changes in the rainforest biome in Central America subject to anthropogenic climate change under two emissions scenarios, RCP4.5 and RCP8.5. The use of a dynamic vegetation model and climate change scenarios is an approach to investigate, assess or anticipate how biomes respond to climate change. In this work, the Inland dynamic vegetation model was driven by the Eta regional climate model simulations. These simulations accept boundary conditions from HadGEM2-ES runs in the two emissions scenarios. The possible consequences of regional climate change on vegetation properties, such as biomass, net primary production and changes in forest extent and distribution, were investigated. The Inland model projections show reductions in tropical forest cover in both scenarios. The reduction of tropical forest cover is greater in RCP8.5. The Inland model projects biomass increases where tropical forest remains due to the CO2 fertilization effect. The future distribution of predominant vegetation shows that some areas of tropical rainforest in Central America are replaced by savannah and grassland in RCP4.5. Inland projections under both RCP4.5 and RCP8.5 show a net primary productivity reduction trend due to significant tropical forest reduction, temperature increase, precipitation reduction and dry spell increments, despite the biomass increases in some areas of Costa Rica and Panama. This study may provide guidance to adaptation studies of climate change impacts on the tropical rainforests in Central America.

We assessed the rainwater chemistry, the potential sources of its main inorganic components and bulk atmospheric deposition in a rural tropical semiarid region in the Brazilian Caatinga. Rainfall samples were collected during two wet seasons, one during an extremely dry year (2012) and one during a year with normal rainfall (2013). According to measurements of the main inorganic ions in the rainwater (H+, Na+, NH4 +, K+, Ca2+, Mg2+, Cl−, NO3 −, and SO4 2−), no differences were observed in the total ionic charge between the two investigated wet seasons. However, Ca2+, K+, NH4 + and NO3 − were significant higher in the wetter year (p < 0.05) which was attributed to anthropogenic activities, such as organic fertilizer applications. The total ionic contents of the rainwater suggested a dominant marine contribution, accounting for 76 % and 58 % of the rainwater in 2012 and 2013, respectively. The sum of the non-sea-salt fractions of Cl−, SO4 2−, Mg2+, Ca2+ and K+ were 19 % and 33 % in 2012 and 2013, and the nitrogenous compounds accounted for 2.8 % and 6.0 % of the total ionic contents in 2012 and 2013, respectively. The ionic ratios suggested that Mg2+ was probably the main neutralizing constituent of rainwater acidity, followed by Ca2+. We observed a low bulk atmospheric deposition of all major rainwater ions during both wet seasons. Regarding nitrogen deposition, we estimated slightly lower annual inputs than previous global estimates. Our findings contribute to the understanding of rainfall chemistry in northeastern Brazil by providing baseline information for a previously unstudied tropical semiarid ecosystem.

The assessment of shelter needs of displaced people in the aftermath of major earthquake events is one the main challenges that emergency responders currently have to face. Based on the scale of the disaster, the short-term shelter demand can turn into a temporary housing need for displaced population, which is a local government responsibility. The study presented in this paper is focused on a critical review of currently available methodologies and corresponding software packages that were developed specifically for estimating the number of displaced people and those who will most likely seek public sheltering and will need temporary housing. The main features and shortcomings of such tools are highlighted and interpreted with a view to future improvement and application in the disaster management field. Two software tools, ERGO-EQ and HAZUS-MH, have been identified as more exhaustive in considering all the different variables involved in the shelter needs estimation. For this reason, this study also includes a full application of those two software tools to a real case study. Specifically, the modelling of the February 22nd, 2011 Christchurch earthquake is presented, in which hazard, vulnerability and exposure (both physical and social) were characterized over a specific area of Christchurch urban area as input to the aforementioned software tools. The employed tools yielded different results in terms of dislocated people and shelter needs estimates, for which a brief discussion is presented on possible ways to improve and to better reflect the local conditions, in order to produce more realistic outputs.

Nas últimas décadas, o clima da Terra vem apresentando mudanças no seu comportamento, através do aumento da frequência de eventos climáticos extremos, associado muito provavelmente às mudanças climáticas globais, cujo tema tornou-se popular e motivo de discussão do público em geral. Neste contexto, o presente estudo apresenta uma análise das frequências dos eventos extremos de seca e chuva na Amazônia baseada em séries de precipitação mensal de quatro bancos de dados: GPCP (Global Precipitation Climatology Project), GPCC (Global Precipitation Climatology Center), CPC (Climate Prediction Center) e Era-Interim, no período de 1979 a 2014. Os eventos extremos de seca e chuva foram caracterizados pelo índice de precipitação padronizada (SPI) aplicado a diferentes escalas temporais (3, 6 e 12 meses). Os resultados mostraram diferenças expressivas nas frequências dos eventos extremos de seca e chuva, nos quatro bancos de dados. Todavia, constatou-se nas três escalas do SPI, em todas as estações do ano e nos quatro bancos de dados que, a Amazônia apresentou frequências de eventos extremos de chuva variando entre 3% a 6% no período em estudo. Por outro lado, observou-se nos eventos extremos de seca uma variação superior a 6% das frequências.

O conhecimento da distribuição espacial e temporal da precipitação, bem como da qualidade de diferentes conjuntos de dados disponíveis, são extremamente necessários para subsidiar estudos observacionais e também para a validação de modelos de previsão numérica de tempo e clima. Desta forma, este trabalho tem como objetivo investigar a consistência dos dados de precipitação provenientes do GPCC, uma vez que, este conjunto possui a maior serie continua de dados de precipitação (de 1901 até o presente), por meio de inter comparações com outros dados de precipitação mensal: GPCP, CPC e Era-interim. Neste estudo o GPCP foi considerado como referência, pois consiste na combinação e incorporação de estimativas de chuva baseadas na combinação de informações de satélite com postos pluviométricos locais. Os resultados mostraram que o padrão sazonal de precipitação foi semelhante nos quatro bancos de dados, porém as diferenças foram notadas no quantitativo de precipitação sazonal estimada em cada fonte de dados. Além disso, as precipitações mensais do GPCC apresentaram valores de viés e RMSE pequenos para as quatros estações do ano, quando comparados com os dados do CPC e Era-Interim. Vale destacar que os dados do GPCP utilizam dados do GPCC e por isso os erros sistemáticos são menores.

No presente estudo foi utilizado o índice de precipitação normalizada (SPI) para identificar e caracterizar os eventos extremos secos na Amazônia, que ocorreram entre os anos de 1979 a 2014. Além disso, foi avaliada a evolução temporal destes eventos e quantificada a dimensão das áreas afetas pelos mesmos. Os resultados mostraram que a seca de 1998 foi uma das mais intensas (SPI médio igual a -1,69) no período estudado. Contudo, pesquisas caracterizaram os anos de 2005 e 2010 como as duas secas mais intensas do século. Desta forma, também foi realizado um estudo comparativo entre essas secas. Sugere-se que o impacto das secas de 2005 e 2010 seja uma resposta as secas ocorridas em 1993-1994 e 1997- 1998, uma vez que, apesar dos anos seguintes apresentarem eventos de chuvas as condições das secas ocorridas na década de 90 foram tão graves que a floresta não foi capaz de se recuperar totalmente.

Given the high and increasing lightning incidence over the Southeast of Brazil and the various impacts that this phenomenon generates to society, there is a growing need in predicting its occurrence, in order to minimize its consequences. In this context, this work presents the development of a methodology for the projection of lightning in the State of São Paulo (Southeastern Brazil), using the HadGEM2-ES and CSIRO-Mk3.6 models in two IPCC climate change scenarios: RCP4.5 and RCP8.5. Since lightning is not an output variable of climate models, tests were carried out to evaluate the relationship between the observed data of oceanic and atmospheric fields, which are known as outputs of the models, and the lightning from the RINDAT and BrasilDAT detection networks. As result, a correlation of 0.84 was obtained. In the projections, it was verified that, while during a large portion of the current climate we observed events of lightning below the average, the future climate reveals the preponderance of anomalously above average events, both in the scenario of intermediate-low emissions (RCP4.5) and in the scenario of high emissions (RCP8.5), suggesting a change in the pattern of the lightning incidence in the State of São Paulo.

A suscetibilidade da região Nordeste do Brasil ao processo de desertificação está associada à variabilidade do clima e a fatores antropogênicos. Nesse contexto, extremos climáticos intensos associados à degradação do solo podem levar à aceleração do processo de desertificação no semiárido. O objetivo do trabalho é avaliar processo de desertificação no estado de Pernambuco e suas projeções para o século XXI. O estudo foi realizado com dados mensais de simulações de precipitação e temperatura do Climatic Research Unit (CRU) e projeções do modelo HADGEM2-ES derivado do Coupled Model Intercomparison Project Phase 5 (CMIP5, utilizados no quinto relatório do Intergovernmental Panel on Climate Change – IPCC-AR5) no cenário RCP 8.5. Para analise, a evapotranspiração potencial foi calculada pelo método de Thornthwaite, que serviu para o cálculo do índice de aridez. O índice de aridez é bastante utilizado nos estudos para a determinação de áreas secas e principalmente nos estudos do processo de desertificação. Os resultados indicaram que, considerando a variabilidade do climática atual e futura no Nordeste do Brasil, associada a ações antrópicas, o estado de Pernambuco tem uma alta suscetibilidade a desertificação.

Changes in land-use systems in tropical regions, including deforestation, are a key challenge for global sustainability because of their huge impacts on green-house gas emissions, local climate and biodiversity. However, the dynamics of land-use and land-cover change in regions of frontier expansion such as the Brazilian Amazon are not yet well understood because of the complex interplay of ecological and socioeconomic drivers. In this paper, we combine Markov chain analysis and complex network methods to identify regimes of land-cover dynamics from land-cover maps (TerraClass) derived from high-resolution (30 m) satellite imagery. We estimate regional transition probabilities between different land-cover types and use clustering analysis and community detection algorithms on similarity networks to explore patterns of dominant land- cover transitions. We find that land- cover transition probabilities in the Brazilian Amazon are heterogeneous in space, and adjacent subregions tend to be assigned to the same clusters. When focusing on transitions from single land- cover types, we uncover patterns that reflect major regional differences in land-cover dynamics. Our method is able to summarize regional patterns and thus complements studies performed at the local scale.

We present a characterization of the chemical composition of the atmosphere of the Brazilian Amazon rainforest based on trace gases measurements carried out during the South American Biomass Burning Analysis (SAMBBA) airborne experiment in September 2012. We analyzed the observations of primary biomass burning emission tracers, i.e., carbon monoxide (CO) and nitrogen oxides (NOx), ozone (O3), isoprene, and its main oxidation products, methyl vinyl ketone (MVK), methacrolein (MACR), and hydroxyhydroperoxides (ISOPOOH). The focus of SAMBBA was primarily on biomass burning emissions, but there were also several flights in areas of the Amazon forest not directly affected by biomass burning, revealing a background with a signature of biomass burning in the chemical composition due to long-range transport of biomass burning tracers from both Africa and the eastern part of Amazonia. We used the [MVK+MACR+ ISOPOOH]/[Isoprene] ratio and the hydroxyl radical (OH) indirect calculation to assess the oxidative capacity of the Amazon forest atmosphere. We compared the background regions (CO<150 ppbv), fresh and aged smoke plumes classified according to their photochemical age ([O3]/[CO]), to evaluate the impact of biomass burning emissions in the oxidative capacity of the Amazon forest atmosphere. We observed that biomass burning emissions disturb the isoprene oxidation reactions, especially for fresh plumes ([MVK+MACR+ISOPOOH]/[isoprene] = 7). The oxidation of isoprene is higher in fresh smoke plumes at lower altitudes (~ 500 m) than in aged smoke plumes, anticipating near the surface a complex chain of oxidation reactions, which may be related to the secondary organic aerosols (SOA) formation. We proposed a refinement of the OH calculation based on the sequential reaction model, which considers vertical and horizontal transport for both biomass burning regimes and background environment. Our approach for the [OH] estimation resulted in values of the same order of magnitude of a recent observation in the Amazon rainforest [OH] ≅ 106 (molecules cm-3 ). During the fresh plume regime, the vertical profile of [OH] and the [MVK+MACR+ISOPOOH]/[isoprene] ratio showed an evidence of an increase of the oxidizing power in the transition from PBL to cloud layer (1,000 1,500 m). These high values of [OH] (1.5  106 molecules cm-3 ) and [MVK+MACR+ISOPOOH]/[isoprene] (7.5) indicate a significant change above and inside the cloud decks due to cloud edge effects on photolysis rates, which have a major impact on OH production rates.