Victor Hugo de Morais Danelichen

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.

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.

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.

CHANGES IN BIOPHYSICAL INDICES DUE TO THE CHANGE OF LAND COVER IN NATIVE CERRADO AREA IN MATO GROSSO STATE

The replacement of natural forests to monoculture can cause changes in local and regional climate due to changes in net radiation and energy exchanges bet...

Estimated net radiation in an Amazon–Cerrado transition forest by Landsat 5 TM

Abstract. The Amazon–Cerrado transition forest is an extensive region with unique characteristics of radiation exchanges. The measurements of the net radiation (Rn) in this ecosystem are limited to the local scale, and their spatial distribution can be carried out by remote sensing techniques, of which accuracy needs to be evaluated. Thus, the objective of this study was to analyze the accuracy of the model of surface Rn derived from measured solar radiation and estimates of normalized difference vegetation index (NDVI), surface albedo (α), and land surface temperature (LST) estimated by images of Landsat 5 TM in an Amazon–Cerrado transition forest. The Rn, NDVI, α, and LST were estimated by Landsat 5 TM images and related to micrometeorological measurements in a tower of the study area. There was seasonality of micrometeorological variables with higher values of incident solar radiation, air temperature, and vapor pressure deficit during the dry season. However, there was no seasonality of Rn. NDVI decreased and α increased during the dry season, while LST was nearly constant. The Rn had negative correlation with α and positive with NDVI. Both instantaneous and daily Rn estimated with Landsat 5 TM images showed high correlation and low error values when compared with Rn measured in the study area.

Relations of vegetation and water indices to volumetric soil water content in the Pantanal of Mato Grosso, Brazil

ABSTRACT The measurement of the spatial distribution of volumetric soil water content in the Pantanal is highly difficult, but it can be performed indirectly from vegetation and water indices estimated by remote sensors. Thus, we assessed the relationship between volumetric soil water content (VSWC) and indices of the vegetation and water by TM Landsat 5 images in pasture and forest in the Pantanal of State of Mato Grosso. The VSWC was measured daily by a TDR on a non-flooded pasture in the Fazenda Miranda (FMI) and on a floodplain monodominant area of Vochysia divergens Pohl in the RPPN SESC Pantanal, locally known as Cambarazal (Cam). The VSWC in FMI was significantly correlated with the local rainfall, but it was 5 months delayed with rainfall in Cam. The temporal dynamics of vegetation and water indices were significantly correlated with VSWC. However, some spectral indices were negatively correlated with VSWC in Cam. It suggested different responses to VSWC in each study site. As the vegetation in FMI is water limited, the biomass increased directly with the VSWC during the wet season. The combined effect of the presence of dense woody vegetation and the occurrence of flooding in Cam influenced on the non-positive correlation between VSWC and vegetation and water indices. This article demonstrates the need for further research on the relationship of VSWC and spectra indices in the Pantanal.

ESTIMATIVAS DE ÍNDICE DE ÁREA FOLIAR DE UMA PASTAGEM POR SENSORIAMENTO REMOTO NO PANTANAL MATO-GROSSENSE

O Pantanal e considerado a maior planicie alagavel do mundo, composto de 70% por Cerrado. Nas ultimas decadas, devido ao avanco da agropecuaria, grande parte deste bioma tem sido convertido em pastagens. O indice de area foliar (IAF) e uma importante medida da cobertura vegetal, pois, controla as trocas de massa e energia de uma superficie vegetada. Dessa forma o objetivo deste trabalho foi avaliar tres metodos de estimativa de indice de area foliar em uma pastagem no norte do Pantanal Mato-Grossense obtidos por medidas de interceptacao de luz e estimadas por dados de sensores orbitais. O estudo foi conduzido em uma pastagem de Brachiaria humidicola localizada na Fazenda Experimental da Universidade Federal de Mato Grosso, no municipio de Santo Antonio de Leverger – MT. Os dados foram coletados no periodo de janeiro de 2006 a fevereiro de 2010, por meio de sensores orbitais (MODIS e satelite Landsat 5) e dados de radiacao fotossinteticamente ativa incidente, refletida e interceptada na area de estudo. O IAF foi estimado pelos metodos de Monsi e Saeki (1953), pelo metodo de Allen (2002) e pelo MODIS. O IAF medido e estimado por Allen (2002) nao apresentaram correlacao com a precipitacao, entretanto, o IAF obtido pelo MODIS apresentou a correlacao mais significativa (p= 0,000) com a precipitacao. O IAF medido nao correlacionou com o estimado por MODIS, mas correlacionou com o estimado pelo metodo de Allen (2002) (p=0,029). Por meio do teste nao-parametrico de Kruskal Wallis verificou-se que os valores estimados pelo produto do MODIS, por Interceptacao de luz (medido) e Allen (2002) apresentaram diferenca significativa entre si na pastagem. O IAF pelos tres metodos apresentaram diferenca significativa em cada estacao (seca e chuvosa) com p<0,05. Mesmo nao havendo correlacao entre o IAF medido e estimado por MODIS, torna-se relevante permitir a possibilidade de estimativa do IAF pelo MODIS, uma vez que a probabilidade de erro foi proxima ao limite de 0,05 (p=0,07).

Avaliação da Difusividade Térmica de um Solo no Norte do Pantanal

As propriedades termicas do solo sao resultantes de um conjunto de fatores nos quais se incluem a sua textura e composicao quimica. Observacoes regulares da temperatura do solo em diferentes profundidades possibilitam identificar o seu comportamento termico e o conhecimento de importantes propriedades, como difusividade termica do solo. Sendo assim, o objetivo deste trabalho foi determinar a difusividade termica do solo de uma pastagem no norte do Pantanal por diferentes metodos. A difusividade termica do solo foi determinada em uma pastagem de Brachiaria humidicola localizada na Fazenda Experimental da Universidade Federal de Mato Grosso em Santo Antonio de Leverger-MT, com coordenadas geograficas (15o47’11’’S; 56o04’47’’O), de longitude oeste e altitude de 120 m acima do nivel do mar. O clima local esta na classe Aw segundo Koppen e o solo foi classificado como PLANOSSOLO HAPICO Eutrofico gleissolico. A temperatura do solo foi realizada a 1, 3, 7, 15, 30, 50 e 57 cm de profundidade por meio de termopares cobre-constantan, conectados a um armazenador de dados. A difusividade termica do solo foi determinada pelos metodos da amplitude, fase, arco-tangente e logaritmico entre os dias 18 a 28 do mes setembro de 2009. Os valores estimados da difusividade termica do solo entre as profundidades de 0,01 a 0,03 m foram 0,0244 cm2 s-1 pelo metodo da amplitude, 0,0723 cm2 s-1 pelo metodo do logaritmico, 0,0190 cm2 s-1 pelo metodo da fase e 0,0004 cm2 s-1 no metodo do arco tangente na profundidade de 0,07 a 0,15 m. Palavras-chave: propriedades termicas do solo, difusividade termica

Uso do Sensoriamento Remoto na Estimativa do Indice de Área Foliar em Floresta Tropical

A estimativa do indice de area foliar (IAF) em ecossistemas florestais e realizada, em sua maioria, por metodos que incluem a intensidade da radiacao eletromagnetica, transmitida atraves do dossel. No entanto, essas tecnicas nao permitem a representacao espacial do IAF. Sendo assim, o objetivo deste trabalho foi avaliar o IAF de uma floresta de transicao Amazonia-Cerrado estimado por dados de sensores orbitais. Para tanto, o IAF estimado pelo METRIC (Mapping EvapoTranspiration with high Resolution and Internalized Calibration) com imagens TM – Landsat 5 e pelo produto MOD15A2 do MODIS (Moderate Resolution Imaging Spectroradiometer) foi validado com medidas locais por interceptacao de luz em uma torre micrometeorologica em 2008. Mapas de distribuicao espacial do IAF foram preparadas para os oito dias considerados. O IAF estimado pelo produto MOD15A2 apresentou concordância com as medidas em campo, enquanto que o METRIC nao se mostrou capaz de produzir valores do IAF similares aqueles obtidos em campo. Mesmo que o METRIC apresentou limitacoes no seu uso, trabalhos futuros sao necessarios para parametrizar a sua equacao para uma maior serie espaco/temporal de dados.