Comparative analysis of MODIS time-series classification using support vector machines and methods based upon distance and similarity measures in the Brazilian cerrado-caatinga boundary

We have mapped the primary native and exotic vegetation that occurs in the Cerrado-Caatinga transition zone in Central Brazil using MODIS-NDVI time series (product MOD09Q1) data over a two-year period (2011–2013). Our methodology consists of the following steps: (a) the development of a three-dimensional cube composed of the NDVI-MODIS time series; (b) the removal of noise; (c) the selection of reference temporal curves and classification using similarity and distance measures; and (d) classification using support vector machines (SVMs). We evaluated different temporal classifications using similarity and distance measures of land use and land cover considering several combinations of attributes. Among the classification using distance and similarity measures, the best result employed the Euclidean distance with the NDVI-MODIS data by considering more than one reference temporal curve per class and adopting six mapping classes. In the majority of tests, the SVM classifications yielded better results than other methods. The best result among all the tested methods was obtained using the SVM classifier with a fourth-degree polynomial kernel; an overall accuracy of 80.75% and a Kappa coefficient of 0.76 were obtained. Our results demonstrate the potential of vegetation studies in semiarid ecosystems using time-series data

The water balance components of undisturbed tropical woodlands in the Brazilian cerrado

Deforestation of the Brazilian cerrado region has caused major changes in hydrological processes. These changes in water balance components are still poorly understood but are important for making land management decisions in this region. To better understand pre-deforestation conditions, we determined the main components of the water balance for an undisturbed tropical woodland classified as "cerrado sensu stricto denso". We developed an empirical model to estimate actual evapotranspiration (ET) by using flux tower measurements and vegetation conditions inferred from the enhanced vegetation index and reference evapotranspiration. Canopy interception, throughfall, stemflow, surface runoff, and water table level were assessed from ground measurements. We used data from two cerrado sites, Pé de Gigante (PDG) and Instituto Arruda Botelho (IAB). Flux tower data from the PDG site collected from 2001 to 2003 were used to develop the empirical model to estimate ET. The other hydrological processes were measured at the field scale between 2011 and 2014 at the IAB site. The empirical model showed significant agreement (<i>R</i>² = 0.73) with observed ET at the daily timescale. The average values of estimated ET at the IAB site ranged from 1.91 to 2.60 mm day⁻¹ for the dry and wet seasons, respectively. Canopy interception ranged from 4 to 20 % and stemflow values were approximately 1 % of the gross precipitation. The average runoff coefficient was less than 1 %, while cerrado deforestation has the potential to increase that amount up to 20-fold. As relatively little excess water runs off (either by surface water or groundwater), the water storage may be estimated by the difference between precipitation and evapotranspiration. Our results provide benchmark values of water balance dynamics in the undisturbed cerrado that will be useful to evaluate past and future land-cover and land-use changes for this region

Monitoramento sazonal e recuperação pós-fogo da vegetação do Cerrado usando dados do sensor MODIS

Monografia (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, 2014.O bioma Cerrado no Distrito Federal (DF) tem importantes formações nativas protegidas por unidades de conservação. No entanto, o bioma no DF é altamente ameaçado devido à expansão urbana. O Cerrado brasileiro apresenta forte contraste sazonal entre a estação seca e a estação chuvosa, a marcante sazonalidade climática exerce forte influência na fenologia da vegetação. O fogo no Cerrado é outra variável que exerce também forte influência na dinâmica do Cerrado. Os efeitos do fogo sobre a vegetação do Cerrado é um processo complexo e ainda está em amplo debate no meio científico. O presente estudo tem como objetivo caracterizar o comportamento sazonal das formações savânicas e campestres do Cerrado no Distrito Federal, relação entre os índices de vegetação (NDVI e EVI) e a precipitação pluviométrica e também a recuperação do vigor da vegetação pós-fogo com o uso de sensoriamento remoto. Selecionaram-se áreas dentro de unidades de conservação sem registro de incêndios e com registro de incêndios. Para construção das séries temporais foram utilizados os índices de vegetação NDVI e EVI do MOD13Q1 acoplado ao sensor MODIS/TERRA. As imagens datam do período de 2000 a 2012, de 250 m a cada 16 dias. Os espectros do NDVI e EVI foram obtidos após a confecção do cubo multitemporal 3D. Os dados de precipitação pluvial foram extraídos das estações de Brasília (1547004) e Taquara (1547013) com dados mensais de 2000 a 2012. A análise da sazonalidade com os índices de vegetação foi estudada somente nas áreas de referência, ou seja, sem queimadas. A transformada de Fourier foi empregada para separar os dados em componentes de diferentes frequências, ou seja, identificar os ciclos sazonais completos. Adicionalmente, foram elaborados gráficos de perfis sazonais e anomalias do NDVI e EVI que é a diferença entre a média mensal de cada ano e a média mensal de todo o período em estudo. O monitoramento pós-fogo foi realizado em áreas com registros de queimadas e em áreas de referência. A transformada de Fourier possibilitou verificar que no Cerrado do DF um ciclo sazonal completo é compreendido em um ano, representado pelo período seco e o período chuvoso. Os dados do MODIS delinearam satisfatoriamente o forte contraste sazonal da vegetação do Cerrado. Verificou-se que a correlação entre o NDVI com a precipitação nas áreas de Cerrado sentido restrito e Campos naturas é maior com dois (2) meses de atraso, para o EVI a maior correlação foi no mês corrente até um (1) mês de atraso. Para o NDVI a quantidade de dias pós-fogo necessários para recuperação das áreas de Cerrado sentido restrito foi em média de 100 e 94 dias em áreas de Campos naturais. Para o EVI em Cerrado sentido restrito foi de 105 dias e 102 dias para áreas de Campos naturais. Os dados do MODIS foram adequados para monitorar a recuperação do vigor da vegetação pós-fogo. Os resultados mostraram o potencial da recuperação das taxas fotossintéticas e vigor da vegetação pós-fogo, no entanto, devem-se atentar os danos à fauna, flora e a beleza cênica. ___________________________________________________________________________ ABSTRACTThe Cerrado biome in the Distrito Federal (DF) has important portions of native vegetation protected for protected areas. However, the biome in DF is highly threatened by urban expansion. The Brazilian Cerrado has a strong seasonal variation from the dry season and the rainy season, the seasonality exert strong influence on vegetation phenology. The fire in the Cerrado is another variable that also strongly influences the dynamic of the Cerrado. The effects of fire on vegetation of the Cerrado is a complex process and still wide discuss in the scientific process. The present study aims to characterize the seasonal behavior of the Cerrado in the Distrito Federal, relationships between vegetation indices (NDVI and EVI) and the rainfall and also the recovery force of post-fire vegetation using remote sensing. We selected areas within protected areas with and without record of fires. We used vegetation index NDVI and EVI of MOD13Q1 from MODIS / TERRA to construction of the time series. The images are from the period 2000-2012, of 250 m every the 16 days. The spectra of NDVI and EVI were obtained after making the 3D cube multitemporal. The rainfall data were extracted from Brasilia (1547004) and Taquara (1547013) stations with monthly data from 2000 to 2012. The analysis of seasonality with the vegetation index was studied only in reference areas. The Fourier transform was used to separate the data into components of different frequencies, in other words, to identify the complete seasonal cycles. Additionally, we elaborate graphics of seasonal profiles of NDVI and EVI and also graphics of anomalies which is the difference between the monthly average each year and monthly average for the entire period under study. The post-fire monitoring was made in areas with records of fires and reference areas. Through the Fourier transform were possible to verify that the Cerrado of DF has a full seasonal cycle in a year, represented by the dry season and the rainy season. The MODIS data satisfactorily defined the strong seasonal contrast of vegetation. We found that the correlation between the NDVI and precipitation in areas of Cerrado sentido restrito and Campos naturais is greater with two (2) months of delay, for the EVI was the highest correlation between the current month up to one (1) month of delay. The number of days required to the NDVI recover post-fire of the areas of Cerrado sentido restrito showed averaged 100 and 94 days in areas of Campos naturais. The number of days required to the EVI recover post-fire of the areas of Cerrado sentido restrito showed averaged 105 and 102 days in areas of Campos naturais. The MODIS data were adequate to monitor the recovery force of post-fire vegetation. The results showed the potential recovery of photosynthetic rates and vigor of vegetation post-fire, however, fire may cause permanent damage to flora, fauna and scenic beauty

Remote Sensing of Savannas and Woodlands

Savannas and woodlands are one of the most challenging targets for remote sensing. This book provides a current snapshot of the geographical focus and application of the latest sensors and sensor combinations in savannas and woodlands. It includes feature articles on terrestrial laser scanning and on the application of remote sensing to characterization of vegetation dynamics in the Mato Grosso, Cerrado and Caatinga of Brazil. It also contains studies focussed on savannas in Europe, North America, Africa and Australia. It should be important reading for environmental practitioners and scientists globally who are concerned with the sustainability of the global savanna and woodland biome

Land-use and environmental changes in the Cerrados of South-Eastern Mato Grosso - Brazil

The human-induced changes of the Earth's land surfaces have been unprecedented, with outcomes often indicating degradation and loss of environmental quality. Mato Grosso State in Brazil, location of the study area, underwent extensive land-use and land-cover changes in recent decades with the rates, patterns and consequences poorly documented until now. In this context, the aim of the present research is to propose a multidisciplinary approach for quantifying historical land-use and environmental changes in the southeast part of this State, where the Cerrado biome (Brazilian savannas) has been intensively converted into agricultural lands. The methodology includes three parts: remote sensing change detection, land vulnerability mapping, and identification of key environmental indicators. Land-use/cover information was extracted from a temporal remote sensing dataset using an object-oriented classification approach, and the changes quantified employing a post-classification method. In addition, the study area was assessed for its vulnerabilities, focusing mainly on erosion risks, wetlands, and areas with limited or no suitability for crops. Finally, key environmental indicators were identified from the preceding steps and analyzed within the Organisation for Economic Co-operation and Development (OECD) Pressure-State-Response (PSR) framework. The results provided an improved mapping of the Cerrados natural vegetation conversion into crops and pastures, and indicate that the Cerrado vegetation was intensively converted and also became more fragmented in the time frame studied. Between 1985 and 2005 the area lost approximately 6491 km 2 of Cerrados (42 %). Modeling based on the Universal Soil Loss Equation indicated significant increase in erosion risk from 1985 to 2005 mainly related to the increase in crop areas and the crops' encroachment into more fragile lands.The identification of environmental indicators rendered complex environmental information more generally accessible by structuring it within the PSR framework.The indicators captured key information about land-use and environmental changes in the area, showing that agricultural expansion is the major human activity exerting pressure on natural resources at a landscape scale, and that the pattern of change included high rates of crop expansion and the use of fragile environments such as wetlands and sandy erodable soils

Spatio-temporal mixed pixel analysis of savanna ecosystems : a review

Reliable estimates of savanna vegetation constituents (i.e., woody and herbaceous vegetation) are essential as they are both responders and drivers of global change. The savanna is a highly heterogenous biome with high variability in land cover types while also being very dynamic at both temporal and spatial scales. To understand the spatial-temporal dynamics of savannas, using Earth Observation (EO) data for mixed-pixel analysis is crucial. Mixed pixel analysis provides detailed land cover data at a sub-pixel level which are essential for conservation purposes, understanding food supply for herbivores, quantifying environmental change, such as bush encroachment, and fuel availability essential for understanding fire dynamics, and for accurate estimation of savanna biomass. This review paper consulted 197 studies employing mixed-pixel analysis in savanna ecosystems. The review indicates that studies have so far attempted to resolve the savanna mixed-pixel issues by using mainly coarse resolution data, such as Terra-Aqua MODIS and AVHRR and medium resolution Landsat, to provide fractional cover data. Hence, there is a lack of spatio-temporal mixed-pixel analysis for savannas at high spatial resolutions. Methods used for mixed-pixel analysis include parametric and non-parametric methods which range from pixel-unmixing models, such as linear spectral mixture analysis (SMA), time series decomposition, empirical methods to link the green vegetation parameters with Vegetation Indices (VIs), and machine learning methods, such as regression trees (RT) and random forests (RF). Most studies were undertaken at local and regional scale, highlighting a research gap for savanna mixed pixel studies at national, continental, and global level. Parametric methods for modeling spatio-temporal mixed pixel analysis were preferred for coarse to medium resolution remote sensing data, while non-parametric methods were preferred for very high to high spatial resolution data. The review indicates a gap for long time series spatio-temporal mixed-pixel analysis of savannas using high resolution data at various scales. There is potential to harmonize the available low resolution EO data with new high-resolution sensors to provide long time series of the savanna mixed pixel, which, according to this review, is missing.The Deutscher Akademischer Austauschdienst and the Federal Ministry of Education and Research (BMBF) within the framework of the Strategy “Research for Sustainability” (FONA).http://www.mdpi.com/journal/remotesensingpm2022Geography, Geoinformatics and Meteorolog

Parques nacionais do Cerrado para além da conservação da biodiversidade : serviços ecossistêmicos culturais e riscos ambientais

Dissertação (mestrado)—Universidade de Brasília, Faculdade UnB Planaltina, Programa de Pós-Graduação em Ciências Ambientais, 2017.As zonas de amortecimento no entorno de unidades de conservação podem minimizar os impactos antrópicos negativos e estimular o uso sustentável dos recursos naturais. Por outro lado, o uso da terra nessas zonas pode potencialmente deteriorar os processos ecológicos e a conservação da biodiversidade dentro da área protegida. Neste estudo, abordamos a interação homem-ambiente nas zonas de amortecimento de 13 Parques Nacionais do Cerrado Brasileiro, sob dupla perspectiva: como ecossistemas vulneráveis sob intensa pressão de conversão do uso da terra e como importantes fontes de serviços que sustentam o bem-estar humano. Foram realizadas duas análises. A primeira teve como objetivo apontar oportunidades para expandir e complementar as atrações turísticas em torno de oito Parques Nacionais abertos para visitação, aproveitando suas vistas panorâmicas. Os métodos foram baseados em atributos biofísicos derivados de sensoriamento remoto, três categorias principais relacionadas à qualidade visual e ecológica e seis indicadores. Os resultados identificaram perfis para os parques selecionados, relacionando suas características biofísicas com seu principal potencial turístico. As topografias mais acidentadas, em geral, foram associadas a maior amplitude de escala visual e complexidade, enquanto topografias planas favorecem serviços recreativos relacionados à água. A segunda análise investigou áreas protegidas mais sensíveis a distúrbios de mudanças do uso e cobertura do solo transportadas por fluxos hidrológicos. A partir de dados de sensoriamento remoto, foram identificados três fatores que influenciam a sensibilidade ambiental, abrangendo características naturais pedológicas e hidrológicas, bem como medidas de exposição à conversão do uso e cobertura do solo na zona de amortecimento. Os resultados revelaram três grupos de parques a serem priorizados para aplicação de medidas de mitigação e prevenção. O grupo classificado como de alto risco sustenta altas taxas de conversão em suas zonas de amortecimento e outras características que agravam os impactos potenciais. O grupo classificado como de alto uso da terra mostrou as maiores taxas de conversão em suas zonas de amortecimento e também deveria ser priorizado para manejo adaptativo. Outro grupo de parques exibiu grande sensibilidade a perturbações nos fluxos hidrológicos e deveria ser direcionado para prevenção de mudanças de cobertura e uso da terra na zona de amortecimento. Embora o estudo tenha focado em Parques Nacionais localizados no Cerrado brasileiro, a área de estudo é representativa de ecossistemas tropicais com relevante riqueza de espécies e alta pressão de conversão do uso da terra.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).Buffer zones around protected areas can minimize negative human impacts and stimulate the sustainable use of natural resources. Conversely, land-use in these zones can potentially deteriorate ecological processes and biodiversity conservation inside the area under protection. In this study, we address human-environment interaction in the buffer zones of 13 Brazilian Cerrado National Parks, with a twofold perspective: as vulnerable ecosystems under land-use change pressure, and as important sources of services that sustain human wellbeing. Two analyses were conducted. The first one was aimed at revealing opportunities to expand and complement the touristic attractions around eight Cerrado National Parks opened for visitation, by taking advantage of their scenic views. The methods were based on remote sensing derived landscape biophysical attributes, three key categories related to visual and ecological qualities and six indicators. Results identified profiles of the selected parks, relating their biophysical characteristics to their main touristic potential. Strong hilly topographies, in general, were associated with wide visual scale and high complexity while flat topographies favored water related recreational services. The second analysis investigated protected areas more sensitive to land use and land cover change disturbances carried by hydrologic flows. Three factors that influence natural areas sensitivity, encompassing soil and hydrologic natural characteristics, and measures of exposure from land use and land cover change in the buffer zone were obtained from remote sensing data. The results revealed three groups of parks to be targeted for prevention and mitigation measures. The group classified as high risk sustains high rates of conversion in their buffer zones and additional characteristics that aggravate potential impacts. The group classified as high land-use exhibited the highest rates of conversion in their buffer zones, and should also be prioritized for adaptive management. Another group of parks exhibited high sensitivity to disturbances from hydrologic flows and should be targeted for prevention of land use and land cover change in the buffer zone. Although our research focused on National Parks located in the Brazilian Cerrado, the studied area is representative of tropical ecosystems with relevant specie richness and high land use conversion pressure