Aplicação do modelo SIB2 na composição de fluxos de superfície observados e modelados em áreas de floresta e pastagem na Amazônia.

Dissertação apresentada ao Programa de Pós- Graduação: Mestrado em Desenvolvimento regional e meio ambiente (PGDRA) da Fundação Universidade Federal de Rondônia (UNIR) como requisito final para a obtenção do título de Mestre em Desenvolvimento regional e meio ambiente. Orientador: Prof. Dr. Antônio Ocimar Manzi.Os sistemas de monitoramento dos fluxos de energia e massa entre a superfície e a atmosfera, apesar de serem robustos, sofrem interrupções no sistema de aquisição de dados decorrentes de vários fatores que envolvem aspectos instrumentais e ambientais. Na Amazônia este tipo de sistema tem sido aplicado intensivamente nos últimos anos, buscando monitorar as trocas de propriedades físicas entre a floresta natural e a atmosfera e também de áreas impactadas. Nesse sentido esse presente trabalho avalia a aplicação de uma estratégia de composição de dados meteorológicos observados e um modelo SiB2 (Simple Biosphere Model), que estima fluxos de energia, vapor de água e dióxido de carbono para vários ecossistemas. Os dados meteorológicos e os fluxos foram medidos em dois sítios experimentais, um de floresta e outro de pastagem no suldeste da Amazônia, durante os anos de 1999 a 2002. Os parâmetros utilizados para fazer as simulações dos dois sítios foram pesquisados na literatura. Dois tipos de simulações foram realizados: no primeiro apenas os dados metereológicos serviram de entrada ao modelo; no segundo a umidade do solo monitorada também foi assimilada pelo modelo. Os resultados dos fluxos de calor latente, calor sensível e de dióxido de carbono simulados foram comparados com as respectivas medidas disponíveis nos dois sítios. Para floresta obteve-se um R2 = 0,95 e (RMSE) = 65,3 W/m2 para o fluxo de calor latente, R2 = 0,99 e (RMSE) = 52,5 W/m2 para o fluxo de calor sensível e R2 = 0,89 e (RMSE) = 4,6 μmol/m2/s para o fluxo de dióxido de carbono. Na pastagem foram encontrados os seguintes valores: R2 = 0,98 e (RMSE) = 49,2 W/m2 para o fluxo de calor latente, R2 = 0,98 e (RMSE) = 16,2 W/m2 para o fluxo de calor sensível e R2 = 0,93 e (RMSE) = 4,8 μmol/m2/s para o fluxo de dióxido de carbono. O modelo SiB2 capturou a tendência de variação e a magnitude das trocas de energia e de dióxido de carbono entre os ecossistemas e a atmosfera. O modelo mostrou-se útil como ferramenta numérica de preenchimento de falhas de fluxos de energia e dióxido de carbono em particular para área de floresta. Na área de pastagem melhorias na representação física dos processos de respiração do ecossistema podem aprimorar os resultados, particularmente para a troca líquida de gás carbônico

Simulated deforestation versus satellite data in Roraima, Northern Amazonia, Brazil

Scenarios for land-use and land-cover change in Amazonia are necessary to support decisions that could prevent the emission of millions of tons of CO2 into the atmosphere. It is therefore important to evaluate models designed to generate future scenarios. The present study evaluated scenarios generated for the 2011-2017 period in Roraima state, in northern Amazonia. Simulated deforestation was compared to PRODES satellite data. The mapping comprised (i) a “silvopastoral use area” (excluding indigenous lands, conservation units and non-forest areas) intersected with (ii) a grid of nine (9) 10,000 km2 (100 × 100 km) cells for evaluations. The 2013 scenario had the greatest similarity (55.2%) with the corresponding PRODES map. Despite divergences between simulated deforestation in the scenarios and PRODES deforestation, the evaluations generally demonstrated the model’s validity and its ability to produce future scenarios that realistically represent the deforestation that occurred in Roraima state during the analyzed period.Cenários de mudança de uso e cobertura da terra na Amazônia são necessários para subsidiar decisões que podem evitar a emissão de milhões de toneladas de CO2 para a atmosfera. Portanto, é importante avaliar modelos que visam a geração de cenários futuros. O atual estudo avaliou cenários gerados para o período 2011-2017 em Roraima, norte da Amazônia. Comparou-se o desmatamento simulado com os dados de satélite do PRODES. O mapeamento compreendeu (i) uma Área de Uso Silvo-pastoril – AUS (excluindo terras indígenas, unidades de conservação e não-floresta) intersectada com (ii) uma grade de nove (9) células de 10.000 km2 (100 × 100 km) para avaliações. O cenário de 2013 apresentou a maior similaridade (55,2%) com o mapa correspondente do PRODES. Apesar das divergências entre o desmatamento simulado nos cenários e o desmatamento oficial, no geral, as avaliações demonstraram a validade do modelo e a sua habilidade para gerar cenários que representam, de forma realística, o desmatamento ocorrido em Roraima no período analisado

Soil phosphorus fractions and their relation to leaf litterfall in a central Amazonian terra firme rainforest

Phosphorus (P) cycling is an important yet poorly studied aspect of the macronutrient balance in tropical rainforest ecosystems. As soil P occurs in different organic and inorganic forms (fractions) with varying degrees of lability, we hypothesized that these fractions will vary between soil types, and temporally within soil types. Additionally, we hypothesized a direct influence of leaf litterfall P input on soil total P and soil P fractions. We collected soil and leaf litter samples from three soil types in a central Amazonian lowland rainforest in Brazil over five months, and used a modified Hedleys fractionation method to determine six organic and inorganic soil P fractions, and also total, labile and residual P. Leaf litterfall P concentrations were determined colorimetrically. Soil inorganic and organic P fractions varied between soil types and across months, but soil type and month interactions were mostly non-significant. Some inorganic P fractions (Pi-NaOH) peaked while the organic fractions (Po-NaOH) fell and vice versa. Leaf litterfall production and leaf litterfall P input peaked around two months following the wettest month. Leaf litterfall P input was a significant predictor of Po-NaHCO3, a bioavailable P fraction. Future studies on P cycling in terrestrial ecosystems should examine the roles played by individual soil P fractions as they cycle asynchronistically and differently across soil types. A ciclagem de fósforo (P), mesmo sendo pouco estudada, é importante para o equilíbrio de macronutrientes em ecossistemas de floresta tropical úmida. Como P no solo ocorre em diferentes formas orgânicas e inorgânicas (frações), com diferentes graus de labilidade, supomos que essas frações variam temporalmente entre os diferentes tipos de solo. Além disso, hipotetizamos uma influência direta da serrapilheira no aporte de P no solo. Coletamos amostras de solo e folhas em três tipos de solo em uma floresta tropical na Amazônia central no Brasil durante cinco meses e usamos o método de fracionamento modificado de Hedley para determinar seis frações orgânicas e inorgânicas de P no solo, bem como P total, lábil e residual. As concentrações de P na serrapilheira foram determinadas pelo método de colorimetria. As frações de P inorgânico e orgânico do solo variaram entre os tipos de solo e ao longo dos meses, mas as interações entre tipo de solo e meses foram majoritariamente não significativas. Algumas frações de P inorgânicas (Pi-NaOH) atingiram o pico enquanto as frações orgânicas (Po-NaOH) caíram e vice-versa. A produção de serrapilheira e a entrada de P atingiram o pico por volta de dois meses após o mês mais chuvoso. A entrada de P da serrapilheira foi um preditor significativo de Po-NaHCO3, uma fração de P biodisponível. Futuros estudos sobre a ciclagem de P nos ecossistemas devem examinar o papel desempenhado pelas frações individuais de P no solo, à medida que circulam de forma assíncrona e diferente entre tipos de solo

Spatial distribution of forest biomass in Brazil's state of Roraima, northern Amazonia

Forest biomass is an important variable for calculating carbon stocks and greenhouse gas emissions from deforestation and forest fires in Brazilian Amazonia. Its spatial distribution has caused controversy due to disagreements over the application of different calculation methodologies. Standardized networks of forest surveys provide an alternative to solve this problem. This study models the spatial distribution and original total stock of forest biomass (Aboveground + Belowground + Fine and coarse litter) in Brazil's state of Roraima, taking advantage of data from georeferenced forest surveys in the region. Commercial volume (bole volume) from surveys was expanded to total biomass. Kriging techniques were used to model the spatial distribution of biomass stocks and generate a benchmark map. All results were associated with phytophysiognomic groups, climatic regions and land uses (protected areas; agricultural use). We estimate forest in the state of Roraima to have an original biomass stock of 6.32 × 109 Mg. Forest biomasses in areas with shorter dry seasons were higher as compared to forests in regions with longer dry seasons. The original vegetation in protected areas, independent of phytophysiognomic group, has higher biomass compared to areas currently under agricultural use. Protected areas support 65.8% of Roraima's stock of forest biomass, indicating an important potential role in REDD projects for conservation of forest carbon. Information on spatial distribution of biomass stocks at a more refined scale is needed to reduce uncertainties about the regional character of carbon pools in Amazonia. © 2016 The Author

Calibration of the simplified simple biosphere model (SSiB) for Amazonian pasture and forest sites using LBA data

The parameters of the Simplified Simple Biosphere Model - SSiB were validated and subsequently calibrated for the Fazenda Nossa Senhora Aparecida (62º22'W; 10º45'S) pasture site and the Reserva Biológica do Jaru (62º22'W; 10º45'S) forest site, both located in the state of Rondônia. Micrometeorological and hydrological data collected during the dry period of 2001, as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - LBA, were used. The results showed that the model simulated well the net radiation, both at the pasture and at the forest. The latent heat flux was super-estimated in both sites. The model sub-estimated the sensible heat flux at the pasture and at the forest, mainly during the night period; notwithstanding, the values for the forest were nearer to the observed ones. With the calibrated parameters, the model generated better estimations of the latent and the sensible heat fluxes, thus better representing the energy partition both at the forest and at the pasture.", 'enOs parâmetros do "Simplified Simple Biosphere Model"-SSiB foram validados e posteriormente calibrados para os sítios de pastagem da Fazenda Nossa Senhora Aparecida (62º22\'W; 10º45\'S) e de floresta da Reserva Biológica do Jaru (62º22\'W; 10º45\'S), ambos situados no estado de Rondônia. Foram utilizadas medidas micrometeorológicas e hidrológicas obtidas durante o período seco de 2001, como parte do Experimento de Grande Escala da Biosfera-Atmosfera na Amazônia - LBA. Os resultados indicam que o modelo simulou bem o saldo de radiação, tanto na pastagem quanto na floresta. O fluxo de calor latente foi superestimado nos dois sítios nos períodos de simulação, o que deve estar relacionado aos parâmetros utilizados no cálculo dessa variável. O modelo subestimou o fluxo de calor sensível na pastagem e na floresta, principalmente no período noturno; porém, para a floresta, os valores foram mais próximos daqueles observados. Com os parâmetros ajustados, melhores estimativas dos fluxos de calor latente e de calor sensível foram geradas e, conseqüentemente, representou melhor as partições de energia na floresta e na pastagem

Effect of smoke and clouds on the transmissivity of photosynthetically active radiation inside the canopy

Biomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes, and thus has implications for photosynthesis within plant canopies. This work reports results from photosynthetically active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biológica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture - Forest Service. Significant reduction of PAR irradiance at the top of the canopy was observed due to the smoke aerosol particles layer. This radiation reduction affected turbulent fluxes of sensible and latent heats. The increase of AOD also enhanced the transmission of PAR inside the canopy. As a consequence, the availability of diffuse radiation was enhanced due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase of CO2 uptake by the vegetation. However, for even higher AOD values, the corresponding NEE was lower than for intermediate values. As expected, water vapor pressure deficit (VPD), retrieved at 28 m height inside the canopy, can also affect photosynthesis. A decrease in NEE was observed as VPD increased. Further studies are needed to better understand these findings, which were reported for the first time for the Amazon region under smoky conditions

Fluxos de CO2 em Plantio de Palma de Óleo no Leste da Amazônia

Terrestrial ecosystems are important for the CO2 exchange between surface and atmosphere. This work presents the atmospheric conditions and CO2 measurements in interspecific hybrid of oil palm in eastern Amazonia, during El Niño year. The experiment was carried out in Moju-Pará, where a micrometeorological tower was installed to obtain meteorological and CO2 data during the period from january to december 2015. The diurnal averages of CO2 uptake peaked at noon, with 22.3 (± 0.98) mol m-2 s-1 in the wet season and 21.0 (± 0.47) mol m-2 s-1 in the dry season. There was little variation in nocturnal averages of CO2 emission, about 5 (± 0.20) mol m-2 s-1, in both wet and dry seasons. The diurnal averages of CO2 concentration were lower and nocturnal averages were higher. Generally, the daily CO2 exchange cycle presented a difference between the wet and dry season. These results contribute to a better understanding of the temporal trend of CO2 fluxes in agricultural crop during drought year in eastern Amazonia, generating new pieces of information about the interaction between oil palm and atmosphere. © 2018, Sociedade Brasileira de Meteorologia. All rights reserved

Avaliação da habilidade do modelo WRF em representar a precipitação na amazônia usando diferentes escalas

Precipitation over the northern Amazon during the austral summer and autumn seasons of the 1988-1999 was simulated using the Regional Weather Research and Forecasting (WRF) model, with downscaling approach with nested domains of 45 and 15 km. The boundary and initial conditions were obtained from the Climate Forecast System Reanalysis (CFSR) of the National Centers for Environmental Prediction (NCEP). The model skill was tested using different rea-nalyzed precipitation datasets that represent different space scales. The bias of the model shows seasonal and spatial dependences, with positive bias in southwestern Brazilian Amazon during summer and in northwestern South America during autumn. The downscaling was needed to reproduce the surface influences on the regional and local systems that affect the rainfall distribution in the region. The WRF model, in general, reproduces the main observed precipitation patterns, without the dry bias, typical of general circulation models (GCM). The results indicate that the dynamic downscaling technique improves the WRF model performance for the seasonal climate forecast in the Amazon region. © 2019, Sociedade Brasileira de Meteorologia. All rights reserved