Marcelo Sacardi Biudes

The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability

Abstract Measurements of ecosystem gas exchange, meteorology, and hydrology (rainfall and soil moisture) were used to assess the seasonal patterns of, and controls on, average diel (24 h) net ecosystem CO2 exchange (NEE), evapotranspiration (E), and bulk canopy water vapor conductance (Gc) of a tropical transitional (ecotonal) forest in the Brazilian Amazon. Diel trends in E and NEE were almost completely explained by the diel variation in photosynthetic photon flux density (QPPFD), and while the QPPFD response of E varied little over the annual cycle, the QPPFD response of NEE declined substantially during the dry season, and the magnitude of hysteresis in the NEE–QPPFD response increased as well. The magnitude of the residuals for the QPPFD versus NEE response was significantly negatively correlated with total monthly rainfall and surface soil moisture and positively correlated with the maximum daily temperature and atmospheric vapor pressure deficit (V). Average daily Gc was also significantly correlat...

Soil CO2 Dynamics in a Tree Island Soil of the Pantanal: The Role of Soil Water Potential

The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO2 research has been conducted in this region. We evaluated soil CO2 dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO2 concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO2 efflux and related environmental parameters. Soil CO2 efflux during the study averaged 3.53 µmol CO2 m−2 s−1, and was equivalent to an annual soil respiration of 1220 g C m−2 y−1. This efflux value, integrated over a year, is comparable to soil C stocks for 0–20 cm. Soil water potential was the measured parameter most strongly associated with soil CO2 concentrations, with high CO2 values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO2 efflux from the tree island soil, with soil CO2 dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO2 efflux from soil. The annual flood arrives later, and saturates soil from below. While CO2 concentrations in soil grew very high under both wetting mechanisms, the change in soil CO2 efflux was only significant when soils were wet from above.

Estimativa do balanço de energia em cambarazal e pastagem no norte do Pantanal pelo método da razão de Bowen

O estudo do balanco de energia de uma superficie vegetada e a atmosfera e importante para caracterizar o microclima local, identificar interacoes entre variaveis ambientais e a vegetacao, e identificar efeitos das atividades antropogenicas. O objetivo deste trabalho foi estimar a variacao sazonal do balanco de energia pelo metodo da razao de Bowen em uma area de vegetacao monodominante de Cambara na RPPN SESC-Pantanal e uma area de pastagem na Fazenda Experimental da UFMT. Os componentes do balanco de energia apresentaram sazonalidade, com maiores medias na estacao chuvosa nas duas areas de estudo. No cambarazal houve maior variacao do fluxo de calor latente da estacao seca para a chuvosa que na pastagem. Entretanto, a variacao sazonal do fluxo de calor sensivel foi menor no cambarazal que na pastagem, devido ao efeito termo-regulador do cambarazal, em funcao da maior biomassa. A energia disponivel aos dois sitios foi destinada prioritariamente em fluxo de calor latente, 80,0% no cambarazal e 56,6% na pastagem, seguido pelo fluxo de calor sensivel, 19,1 e 42,9%, e pelo fluxo de calor no solo, 0,3 e 7,2%.

Modelling gross primary production of a tropical semi-deciduous forest in the southern Amazon Basin

Semi-deciduous forest in the Amazon Basin is sensitive to temporal variation in surface water availability that can limit seasonal rates of leaf and canopy gas exchange. We estimated the seasonal dynamics of gross primary production (GPP) over 3 years (2005–2008) using eddy covariance and assessed canopy spectral reflectance using MODIS imagery for a mature tropical semi-deciduous forest located near Sinop, Mato Grosso, Brazil. A light-use efficiency model, known as the Vegetation Photosynthesis Model (VPM), was used to estimate seasonal and inter-annual variations in GPP as a function of the enhanced vegetation index (EVI), the land surface water index (LSWI), and local meteorology. Our results indicate that the standard VPM was incapable of reproducing the seasonal variation in GPP, primarily because the model overestimated dry-season GPP. In the standard model, the scalar function that alters light-use efficiency (εg) as a function of water availability (Wscalar) is calculated as a linear function of the LSWI derived from MODIS; however, the LSWI is negatively correlated with several measures of water availability including precipitation, soil water content, and relative humidity (RH). Thus, during the dry season, when rainfall, soil water content, and RH are low, LSWI, and therefore, Wscalar, are at a seasonal maximum. Using previous research, we derived new functions for Wscalar based on time series of RH and photosynthetic photon flux density (PPFD) that significantly improved the performance of the VPM. Whether these new functions perform equally well in water stressed and unstressed tropical forests needs to be determined, but presumably unstressed ecosystems would have high cloud cover and humidity, which would minimize variations in Wscalar and GPP to spatial and/or temporal variation in water availability.

Net radiation estimated by remote sensing in Cerrado areas in the Upper Paraguay River Basin

Abstract The Cerrado is a heterogeneous landscape which is shrinking due to deforestation, giving rise to managed ecosystems. The land cover changes alter net radiation (Rn), which determines the quantity of available energy to the energy balance partition. The objectives of this study were (1) to determine the spatial pattern of the vegetation indices, albedo, and land surface temperature (LST) and (2) to evaluate the Rn estimated by Landsat 5 Thematic Mapper (TM) images over Cerrado areas in the Upper Paraguay River Basin. We estimated the vegetation indices, albedo, LST, and Rn of five selected vegetation types. The values estimated by Landsat 5 TM images had seasonal variations with higher values of the vegetation indices and lower values of the albedo and the LST during the wet season. The riparian and Cerrado strictu sensu had higher values of vegetation indices and lower albedo and LST than grasslands. The Rn estimated by Landsat 5 TM images was highly correlated with the measured Rn. The Rn had a seasonal pattern, following the solar radiation, with higher values during the wet season and varied spatially with higher values in the riparian forest and Cerrado strictu sensu and lower in the grasslands. This study showed the applicability of the Landsat 5 TM images to estimate Rn, which can help to understand the heterogeneity in the study area.

Estimation of gross primary production of the Amazon-Cerrado transitional forest by remote sensing techniques

The gross primary production (GPP) of ecosystems is an important variable in the study of global climate change. Generally, the GPP has been estimated by micrometeorological techniques. However, these techniques have a high cost of implantation and maintenance, making the use of orbital sensor data an option to be evaluated. Thus, the objective of this study was to evaluate the potential of the MODIS (Moderate Resolution Imaging Spectroradiometer) MOD17A2 product and the vegetation photosynthesis model (VPM) to predict the GPP of the Amazon-Cerrado transitional forest. The GPP predicted by MOD17A2 (GPPMODIS) and VPM (GPPVPM) were validated with the GPP estimated by eddy covariance (GPPEC). The GPPMODIS, GPPVPM and GPPEC have similar seasonality, with higher values in the wet season and lower in the dry season. However, the VPM performed was better than the MOD17A2 to estimate the GPP, due to use local climatic data for predict the light use efficiency, while the MOD17A2 use a global circulation model and the lookup table of each vegetation type to estimate the light use efficiency.

ESTIMATIVA DA EVAPOTRANSPIRAÇÃO NUMA PASTAGEM MISTA, EM CONDIÇÕES DE CERRADO, PELOS MÉTODOS DE RAZÃO DE BOWEN E PENMAN-MONTEITH

SummaryThe objective of this work was to determine the energy balanceand the evapotranspiration by the Bowen ratio method and to comparewith the reference evapotranspiration obtained with the Penman-Monteith™sModel of a mixed pasture composed of three types of species: Panicummaximum, Elyonurus muticus and Brachiaria humidicola in cerradoconditions, of september to december of 2006. The experiment wasconducted in the Experimental Farm of the Universidade Federal de MatoGrosso, in Santo Antonio do Leveger - MT, where the AgrocilmatologicalStation Ricardo Remetter is located to 50 m of the study location. Thetemperature and vapor pressure values were measured in the heights 0,55,1,00 and 1,55 m (levels 1, 2 and 3). The energy balance estimate wassatisfactory when it used the levels gradients 1-2 and 1-3, with reliable index(c) of 0,87. However, the energy balance estimated in the levels 2-3 hadvalues of the Bowen ratio outside the reliable limit (-0,5 and 0,5) and reliableindex (c) of 0,73, being smaller than the levels 1-2 and 1-3. The radiationbalance was used mainly as latent heat, being affected by the meteorologicalvariable and by water availability in the soil.Key words: water use, energy balance, Willmott index.IntroducaoA producao de bovinos em regime de pastagem tem se tornadouma forte tendŒncia da pecuAEria mundial na atualidade. Embora apresenteum menor custo de producao, esse sistema faz parte de um processo deinteracao entre crescimento da planta forrageira, utilizacao da forragemproduzida, e sua conversao em produto animal (Teixeira et al., 2005).Ecossistemas de pastagens sao entidades bastante complexas, epossuem uma sOrie de componentes bioticos e abioticos que interagem entresi de diferentes maneiras (Silva & Pedreira, 1997). Os ciclos de crescimen-to das gramineas sao em muito influenciados pelas variAEveis meteorologicas,tais como temperatura, AEgua e luz, os quais determinam todo o desenvolvi-mento dessas plantas, quando nao considerado o potencial genOtico dasmesmas (Soria, 2002).A irrigacao de pastagens no Brasil apresentou crescimento acen-tuado a partir da dOcada de 1990, existindo, atualmente, dezenas de equipa-mentos do tipo pivo-central. Com essa nova prAEtica, os pecuaristas, princi-palmente do Centro-Oeste e do Nordeste brasileiro, obtiveram, inicial-mente, resultados satisfatorios. PorOm, com o passar dos anos, devido aomanejo inadequado da irrigacao e a falta de recomendacies tOcnicas empastagens, os resultados passaram a ser insatisfatorios (Silva et al., 2005).A determinacao do consumo hidrico, por meio da estimativa

Estimation of soil heat flux in a neotropical Wetland region using remote sensing techniques

The direct estimation of the soil heat flux (G) by remote sensing data is not possible. For this, several models have been proposed empirically from the relation of G measures and biophysical parameters of various types of coverage or not vegetated in different places on earth. Thus, the objective of this study was to evaluate the relation between G/Rn ratio and biophysical variables obtained by satellite sensors and evaluate the parameterization of different models to estimate G spatially in three sites with different soil cover types. The net radiation (Rn) and G were measured directly in two pastures at Miranda Farm and Experimental Farm and and Monodominant Forest of Cambara. Rn, G, and G/Rn ratio and MODIS products, such as albedo (α), surface temperature (LST), vegetation index (NDVI) and leaf area index (LAI) varied seasonally at all sites and inter-sites. The sites were different from each other by presenting different relation between measures of Rn, G and G/Rn ratio and biophysical parameters. Among the original models, the model proposed by Bastiaanssen (1995) showed the best performance with r = 0.76, d = 0.95, MAE = 5.70 W m-2 and RMSE = 33.68 W m-2. As the reparameterized models, correlation coefficients had no significant change, but the coefficient Willmott (d) increased and the MAE and RMSE had a small decrease.

EFFECT OF WEATHER CONDITIONS ON THE RISK OF FIRE AND THE NUMBER OF URBAN BURNINGS AND FIRES RECORDED BY REMOTE SENSING IN CUIABÁ-MT, BRAZIL

The establishment of urban fires prevention policies can be defined from studies about its causes. Urban fires are aggravated by specific weather conditions, such as lack of precipitation, high wind speed and low relative humidity, besides it has been related to human activities. The number of fires in the city of Cuiaba MT is high during dry season, which affect the health of the population. Thus, the objective of this study was (i) assess the seasonality of fires attended by the Fire Department and the burnings obtained from satellite imagery; (ii) calculate the Monte Alegre (FMA) and Altered Monte Alegre (FMA+) Formulas; and (iii) correlate fires, burnings, FMA, FMA+, air temperature and rainfall between 2005 and 2009 in Cuiaba/MT. For this, we used the database of the number of occurrences of urban fires attended by the Fire Department Cuiaba MT obtained from Centro Integrado de Operacoes de Seguranca Publica de Mato Grosso (CIOSP) and the number of burnings obtained from Divisao de Geracao de Imagens (DGI) of the Instituto Nacional de Pesquisas Espaciais (INPE) between January 2005 and December 2009. The FMA and FMA+ indices were calculated using the daily precipitation and wind speed and relative humidity measured at 13 o’clock on the Centro Integrado de Defesa Aerea e Controle de Trafego Aereo (CINDACTA I), located in Aeroporto Internacional Marechal Cândido Rondon. The precipitation, air temperature and relative humidity varied annually and seasonally with higher values during the rainy season. The largest number of fires and burnings occurred in the late dry season (August and September), due to low rainfall and relative humidity. The FMA and FMA+ indices were sensitive to weather variations and correlated strongly with the number of fires and burnings without lag, with higher values during the dry season. The FMA and FMA+ indexes can be used to predict future occurrence of fires in Cuiaba-MT.

Trocas gasosas de uma espécie lenhosa na floresta de transição amazônia - cerrado

As florestas de transicao parecem ter um balanco de CO2 nulo, porem as mudancas climaticas que tem ocorrido, como a seca prolongada, podem alterar esse equilibrio a longo prazo. Desta forma, o presente trabalho teve como objetivo estudar as variaveis fisiologicas: fotossintese, fotorrespiracao e respiracao, e entender como essas variaveis podem ser afetadas pelas variacoes sazonais e a posicao da folha na copa da arvore de uma especie vegetal caracteristica de floresta de transicao Amazonia-Cerrado, a Brosimum lactescens S Moore (Moraceae). Utilizando-se um sistema portatil LI-6400 (LI-COR, Inc., Lincoln, NE, USA), as medidas foram realizadas mensalmente. Verificou-se que na estacao seca, houve um incremento substancial na densidade de fluxo fotossinteticamente ativo, DFFA, elevando o deficit de pressao de vapor (DPV). Visando reduzir as perdas de agua, a planta tende a promover o fechamento dos estomatos, havendo uma diminuicao da condutância estomatica (gs), reduzindo assim tambem a concentracao de carbono interno (Ci). Como consequencia, verificou-se que a fotossintese comportou-se de maneira descendente. Contudo. Nesse contexto, como estrategia para dissipacao de energia em excesso, a fotorrespiracao (Rp) aumentou e de forma analoga a respiracao (Rd) tambem aumentou. Os resultados encontrados neste estudo sugerem que variacoes na distribuicao da precipitacao alteram significativamente as trocas gasosas da especie estudada.