Woody plant encroachment in a seasonal tropical savanna: lessons about classifiers and accuracy from UAV images.

Abstract: Woody plant encroachment in grassy ecosystems is a widely reported phenomenon associated with negative impacts on ecosystem functions. Most studies of this phenomenon have been carried out in arid and semi-arid grasslands. Therefore, studies in tropical regions, particularly savannas, which are composed of grassland and woodland mosaics, are needed. Our objective was to evaluate the accuracy of woody encroachment classification in the Brazilian Cerrado, a tropical savanna. We acquired dry and wet season unmanned aerial vehicle (UAV) images using RGB and multispectral cameras that were processed by the support vector machine (SVM), decision tree (DT), and random forest (RF) classifiers. We also compared two validation methods: the orthomosaic and in situ methods. We targeted two native woody species: Baccharis retusa and Trembleya parviflora. Identification of these two species was statistically (p < 0.05) most accurate in the wet season RGB images classified by the RF algorithm, with an overall accuracy (OA) of 92.7%. Relating to validation assessments, the in situ method was more susceptible to underfitting scenarios, especially using an RF classifier. The OA was higher in grassland than in woodland formations. Our results show that woody encroachment classification in a tropical savanna is possible using UAV images and field surveys and is suggested to be conducted during the wet season. It is challenging to classify UAV images in highly diverse ecosystems such as the Cerrado; therefore, whenever possible, researchers should use multiple accuracy assessment methods. In the case of using in situ accuracy assessment, we suggest a minimum of 40 training samples per class and to use multiple classifiers (e.g., RF and DT). Our findings contribute to the generation of tools that optimize time and cost for the monitoring and management of woody encroachment in tropical savannas

LAND USE/ COVER (LULC) MAPPING IN BRAZILIAN CERRADO USING NEURAL NETWORK WITH SENTINEL-2 DATA

The Sentinel-2a and 2B satellites form a multispectral imaging mission for Earth observation. They have promising characteristics for the study of soils and vegetation cover, and their data can be applied for land use/cover (LULC) mapping. To this end, neural networks have shown good results in pattern recognition tasks in orbital images. In this sense, the study aimed to evaluate the use of Sentinel 2 (ESA) image for LULC mapping in the Cerrado Biome, through the application of artificial neural network methodology. Among the classes of use and occupation examined, 8 classes were selected, 4 of which were natural (water bodies, savanna, forest and field formation) and 4 anthropic (Pasture, Urban areas, Silviculture and Seasonal Crop). The classification system by artificial neural network (ANN) was considered successful, with thematic accuracy (Kappa coefficient) of 0.77. Although there are still some thematic confusions during the classification process, the classification results were considered superior when compared to the MaxVer classifier. The Sentinel-2 image, together with the use of a neural network, was shown a good input for carrying out this type of mapping.Key words: Orbital Remote Sensing System, Supervised Classification Techniques, LULC classes

Predicting the potential distribution of aquatic herbaceous plants in oligotrophic Central Amazonian wetland ecosystems

Aquatic herbaceous plants are especially suitable for mapping environmental variability in wetlands, as they respond quickly to environmental gradients and are good indicators of habitat preference. We describe the composition of herbaceous species in two oligotrophic wetland ecosystems, floodplains along black-water rivers (igapo) and wetlands upon hydromorphic sand soils (campinarana) in the Parque Nacional do Jau and the Reserva de Desenvolvimento Sustentavel Uatuma in Central Amazonia, both protected areas. We tested for the potential distribution range (PDR) of the most frequent species of these ecosystems, which are the ones that occurred in at least two of the sampled wetlands, using species distribution models (SDMs). In total, 98 aquatic herbaceous species were recorded, of which 63 occurred in igapos and 44 in campinaranas. Most igapo species had ample PDRs across the Neotropics, while most campinaranas species were restricted to the Amazon Basin. These results are congruent with studies that described similar distribution patterns for tree and bird species, which emphasizes a high degree of endemism in Amazonian campinarana. However, we also found differences in the potential distribution of species between the two protected areas, indicating high environmental variability of oligotrophic ecosystems that deserve further investigation to develop effective measures for their conservation and protection

Mapping Three Decades of Changes in the Brazilian Savanna Native Vegetation Using Landsat Data Processed in the Google Earth Engine Platform.

Widespread in the subtropics and tropics of the Southern Hemisphere, savannas are highly heterogeneous and seasonal natural vegetation types, which makes change detection (natural vs. anthropogenic) a challenging task. The Brazilian Cerrado represents the largest savanna in South America, and the most threatened biome in Brazil owing to agricultural expansion. To assess the native Cerrado vegetation (NV) areas most susceptible to natural and anthropogenic change over time, we classified 33 years (1985?2017) of Landsat imagery available in the Google Earth Engine (GEE) platform. The classification strategy used combined empirical and statistical decision trees to generate reference maps for machine learning classification and a novel annual dataset of the predominant Cerrado NV types (forest, savanna, and grassland). We obtained annual NV maps with an average overall accuracy ranging from 87% (at level 1 NV classification) to 71% over the time series, distinguishing the three main NV types. This time series was then used to generate probability maps for each NV class. The native vegetation in the Cerrado biome declined at an average rate of 0.5% per year (748,687 ha yr?1), mostly affecting forests and savannas. From 1985 to 2017, 24.7 million hectares of NV were lost, and now only 55% of the NV original distribution remains. Of the remnant NV in 2017 (112.6 million hectares), 65% has been stable over the years, while 12% changed among NV types, and 23% was converted to other land uses but is now in some level of secondary NV. Our results were fundamental in indicating areas with higher rates of change in a long time series in the Brazilian Cerrado and to highlight the challenges of mapping distinct NV types in a highly seasonal and heterogeneous savanna biome

A SENSIBILIDADE DA EVAPOTRANSPIRAÇÃO PARA USOS DO SOLO E TOPOGRAFIA EM ÁREA DO BIOMA CERRADO – BRASIL

Evapotranspiration (ET) is a crucial element in the spatiotemporal dynamics of moisture, energy, and heat, and is related to climatic, pedogeomorphological, and phytophysiognomic aspects of the landscape. Therefore, estimating ET requires dynamic and integrated temporal analysis with biophysical landscape factors. The study aimed to analyze the behavior of ET through the analysis of land use and land cover and topographic in time series. The Simple Algorithm for Evapotranspiration Recovery (SAFER) model was used to obtain the variable ET in the periods of 01/21, 02/22, 05/13 and 06/30/2019 (variables). A database of explanatory covariates was constructed, including land use and land cover, satellite image data (Landsat-8) and digital elevation model (SRTM). The values of variables and covariates were extracted into a grid of points and separated for three altimetric conditions, and the linear Gaussian Models (GLM) were applied to the point data. The most explanatory spectral covariates for the ET variation were Albedo and Surface Temperature. And the covariates related to topography were Digital Elevation Model and Topographic Moisture Index. In general, the wet period presents a higher ET rate (2.06 mm d-¹). Forests generated the highest ET regardless of period (1.62 mm d-¹ to 4.03 mm d-¹). Elevated topography also influences the increase in ET in relation to the same lower altimetry classes (A2 and A3). This influence is associated with the altitude dynamics and intrinsic elements of the region, such as the marshy environment in the A3 region, where the highest ET values occurred. This work stands out from its peers for addressing the influence of landscape aspects on the knowledge of evapotranspiration variation, a vanguard theme in the scope of spatial analysis.A evapotranspiração (ET) é um elemento crucial na dinâmica espaço-temporal de umidade, energia e calor, e está relacionada a aspectos climáticos, pedogeomorfológicos e fitofisionômicos da paisagem. Portanto, estimar ET requer análise temporal dinâmica e integrada com fatores biofísicos da paisagem. O estudo teve como objetivo analisar o comportamento do ET por meio da análise do uso e cobertura do solo e da topográficas em série temporal. O modelo Algoritmo Simples para Recuperação da Evapotranspiração (SAFER) foi utilizado para obter a variável ET nos períodos de 21/01, 22/02, 13/05 e 30/06/2019 (variáveis). Um banco de dados de covariáveis explicativas foi construído, incluindo uso e cobertura do solo, dados de imagem de satélite (Landsat-8) e modelo digital de elevação (SRTM). Os valores das variáveis e covariáveis foram extraídos para uma grade de pontos e separados para três condições altimétricas, e nos dados pontuais foram aplicados os Modelos Lineares Gaussianos (GLM). As covariáveis espectrais mais explicativas para a variação de ET foram Albedo e Temperatura da Superfície. E as covariáveis relacionadas à topografia foram Modelo Digital de Elevação e Índice de Umidade Topográfica. Em geral, o período úmido apresenta maior taxa de ET (2,06 mm d-¹). As Florestas geraram a maior ET independente do período (1,62 mm d-¹ a 4,03 mm d-¹). A topografia elevada também influencia no aumento do ET em relação às mesmas classes de altimetria inferior (A2 e A3). Essa influência está associada à dinâmica de altitude e a elementos intrínsecos da região, como o ambiente pantanoso na região A3, onde ocorreram os maiores valores de ET. Este trabalho destaca-se dos pares por abordar a influência de aspectos da paisagem no conhecimento da variação da evapotranspiração, tema de vanguarda no âmbito da análise espacial

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

The sensitivity of evapotranspiration for land uses and topography in area of Cerrado Biome - Brazil.

Abstract: Evapotranspiration (ET) is a crucial element in the spatiotemporal dynamics of moisture, energy, and heat, and is related to climatic, pedogeomorphological, and phytophysiognomic aspects of the landscape. Therefore, estimating ET requires dynamic and integrated temporal analysis with biophysical landscape factors. The study aimed to analyze the behavior of ET through the analysis of land use and land cover and topographic in time series. The Simple Algorithm for Evapotranspiration Recovery (SAFER) model was used to obtain the variable ET in the periods of 01/21, 02/22, 05/13 and 06/30/2019 (variables). A database of explanatory covariates was constructed, including land use and land cover, satellite image data (Landsat-8) and digital elevation model (SRTM). The values of variables and covariates were extracted into a grid of points and separated for three altimetric conditions, and the linear Gaussian Models (GLM) were applied to the point data. The most explanatory spectral covariates for the ET variation were Albedo and Surface Temperature. And the covariates related to topography were Digital Elevation Model and Topographic Moisture Index. In general, the wet period presents a higher ET rate (2.06 mm d-¹). Forests generated the highest ET regardless of period (1.62 mm d-¹ to 4.03 mm d-¹). Elevated topography also influences the increase in ET in relation to the same lower altimetry classes (A2 and A3). This influence is associated with the altitude dynamics and intrinsic elements of the region, such as the marshy environment in the A3 region, where the highest ET values occurred. This work stands out from its peers for addressing the influence of landscape aspects on the knowledge of evapotranspiration variation, a vanguard theme in the scope of spatial analysis

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

O cerrado além das fronteiras : padrões de diversidade e ameaças presentes e futuras à sua flora na Bolívia, Brasil e Paraguai

Orientador: Dr. Franklin GalvãoCoorientadores: Dr. Paulo De Marco Júnior, Dr. Fabricio VillalobosTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Engenharia Florestal. Defesa : Curitiba, 06/03/2018Inclui referências: p.153-175Área de concentração: Conservação da NaturezaResumo: No primeiro capítulo " Using worldwide edaphic data to model plant species niches: an assessment at a continental extent ", foi abordado as seguintes questões principais: (i) Qual é a influência de distintas variáveis preditoras (por exemplo, climática vs. edáfica) em diferentes algoritmos empregados em modelos de nicho ecológico (ENM's, em inglês)? (ii) Qual é a relação entre o desempenho de diferentes preditores e as características geográficas das espécies? Utilizou-se 125 espécies de plantas distribuídas na região Neotropical para explorar o efeito de usar dados edáficos disponíveis no banco de dados SoilGrids e sua combinação com dados climáticos do CHELSA. Além disso, essas diferentes variáveis foram relacionadas com as características geográficas das espécies e diferentes algoritmos. O uso de diferentes preditores (climáticos, edáficos e ambos) afetou significativamente o desempenho do modelo e a complexidade espacial das previsões. Foi demostrado que o uso simultâneo de variáveis climáticas e edáficas geram ENM's com acurácia similar ou melhor que as construídas apenas com variáveis climáticas. Além disso, o desempenho de modelos que consideram essas diferentes variáveis preditoras, separadamente ou em conjunto, teve uma relação com as propriedades geográficas das ocorrências das espécies, como o número e a amplitude de distribuição. A grande extensão geográfica, a variabilidade dos ambientes e as características geográficas das diferentes espécies consideradas permitiram demonstrar que os dados edáficos globais agregam informações úteis para ENM's da planta. Isto é particularmente valioso para estudos de espécies que ocorrem em regiões onde informações mais detalhadas sobre propriedades do solo são pobres ou não existem. No segundo capítulo "Looking beyond borders: patterns of richness and rarity of the Cerrado flora and its transboundary conservation opportunities", foi estuado a flora do Cerrado de forma transfronteiriça para (i) prever padrões de riqueza e raridade de espécies para Bolívia, Brasil e Paraguai, (ii) estudar a concentração de espécies raras a nível global e regional, e (iii) avaliar áreas que apresentam oportunidades e conflitos para conservar a riqueza e a raridade do Cerrado nas três nações. Foi utilizado sete técnicas de modelagem de nicho ecológico para modelar 1559 espécies de plantas do Cerrado. Definimos cenários de oportunidade e conflito para a conservação com base na relação entre o grau de alteração da paisagem e a riqueza e concentração da raridade global e local. A maior concentração de riqueza de espécies e raridade global são encontradas na parte central da ecorregião do Cerrado no Brasil. A Bolívia é o segundo país com maior riqueza e raridade, principalmente associado ao Cerrado e à Floresta Seca Chiquitana. No Paraguai, a riqueza e a raridade estavam concentradas na parte norte do Chaco Úmido e Chaco Seco. Oportunidades e conflitos de conservação foram diferentes para cada país devido à interação entre a diversidade e os padrões de uso da terra. Na medida do nosso conhecimento, esta é a primeira tentativa de descrever a diversidade vegetal do bioma Cerrado além dos limites políticos brasileiros. Apesar de grande parte da flora do Cerrado estar concentrada no Brasil, este país também possui a maior proporção de seu território em um cenário de conflito onde a maior alteração de paisagem ocorre em áreas com maior diversidade. No entanto, foram encontradas grandes oportunidades de conservação na Bolívia e no Paraguai, porque a riqueza e a raridade de espécies preditas estendem-se em áreas com baixo grau de alteração, tornando-os países importantes para conservar a flora do Cerrado. O terceiro capítulo "A dark scenario for Cerrado plant species, effects of future climate, land use and inefficiency of protected areas" teve como objetivo (i) avaliar o efeito da mudança climática e do uso da terra na distribuição das espécies de plantas do Cerrado para diferentes países onde ocorre, (ii) avaliar a eficiência da atual rede de áreas protegidas para salvaguardar espécies sob diferentes emissões de gases de efeito estufa e uso da terra, e (iii) estimar o grau de ameaça de espécies causada pela eficiência de proteção e perda de habitat. Foi mostrado que as mudanças climáticas e a mudança do uso da terra poderiam causar grandes danos à flora do Cerrado até 2050 e 2080, mesmo em condições otimistas. Infelizmente, a maior intensidade e expansão do uso da terra ocorrerá nas regiões onde a maior riqueza será abrigada. A conservação das espécies será seriamente afetada, uma vez que a rede de áreas protegidas não é tão eficiente para protegê-las em condições atuais ou futuras. O baixo nível de proteção, junto às perdas causadas pelo avanço da fronteira agrícola levará a que a maioria das espécies seja altamente ameaçada. As estratégias de conservação do Cerrado devem ser implementadas tanto a nível nacional e como transfronteiriço devido a que o clima e os efeitos do uso da terra foram diferentes em cada país. Palavra-chave: Modelos de distribuição espécies. Mudanças climáticas. Padrões de riqueza. Perda de hábitat. Raridade. Variáveis edáficasAbstract: Cerrado beyond borders: diversity patterns and current and future threats it its flora in Bolivia, Brazil and Paraguay. Abstract: In the first chapter "Using worldwide edaphic data to model plant species niches: an assessment at a continental extent" we address the following main questions: What is the influence of distinct predictor variables (e.g. climatic vs edaphic) on different ENM algorithms? and what is the relationship between the performance of different predictors and geographic characteristics of species? We used 125 plant species distributed over the Neotropical region to explore the effect on ENMs of using edaphic data available from the SoilGrids database and its combination with climatic data from the CHELSA database. In addition, we related these different predictor variables to geographic characteristics of the target species and different ENM algorithms. The use of different predictors (climatic, edaphic, and both) significantly affected model performance and spatial complexity of the predictions. We showed that the use of global edaphic plus climatic variables generates ENMs with similar or better accuracy compared to those constructed only with climate variables. Moreover, the performance of models considering these different predictors, separately or jointly, was related to geographic properties of species records, such as number and distribution range. The large geographic extent, the variability of environments and the different species' geographical characteristics considered here allowed us to demonstrate that global edaphic data adds useful information for plant ENMs. This is particularly valuable for studies of species that are distributed in regions where more detailed information on soil properties is poor or does not even exist. In the second chapter "Looking beyond borders: patterns of richness and rarity of the Cerrado flora and its transboundary conservation opportunities" we studied the flora of Cerrado in a transboundary way to (i) predict species richness and rarity patterns for Bolivia, Brazil, and Paraguay, (ii) study the concentration of rare species at global and regional levels and (iii) evaluate areas presenting opportunities and conflicts to conserve the plant richness and rarity of Cerrado across these three nations. We defined scenarios of opportunity and conflict for conservation based on the relationship between the degree of landscape alteration and the richness and concentration of global and local rarity. Rarity index was based on species geographic range sizes, marginality, and specificity of their niches. The greatest concentration of species richness and global rarity of Cerrado's plant species is found in the central part of the Cerrado ecoregion in Brazil. Bolivia is the second country with the highest richness and rarity, mainly associated with Cerrado and Chiquitano Dry Forest. In Paraguay, richness and rarity were concentrated in the northern part of the Humid and Dry Chaco. Opportunities and conflicts for conservation were different for each country resulting from the interaction between diversity and land-use patterns. To the extent of our knowledge, this is the first attempt to describe the plant diversity of the Cerrado biome beyond Brazilian borders. Despite much of the Cerrado flora being concentrated in Brazil, this country also has the greatest proportion of its territory under a conflict scenario where the major landscape alteration happens in areas with the highest diversity. However, high opportunities for conservation were found in Bolivia and Paraguay where species richness and rarity concentrate in areas with low alteration degree, which makes them important countries to conserve the flora of Cerrado. "A dark scenario for Cerrado plant species, effects of future climate, land use and inefficiency of protected areas" We aimed to (i) assess the effect of the climate change and landuse on the distribution of the Cerrado plant species for different countries where it occurs, (ii) evaluate the efficiency of the current protected area network to safeguards species under different greenhouse-gas emissions and land-use and (iii) estimate the vulnerability of species caused by protection efficiency and habitat loss. We demonstrate that climate change and land-use will cause great damage to Cerrado flora by 2050 and 2080, even under optimistic conditions. Unfortunately, the greatest intensity and extent of land-use will have to overcome on the regions where the greatest richness will be harbored. The conservation of the species will be seriously affected since the protected areas network is not as efficient in safeguarding them under current or future conditions. The low level of protection together with the losses caused by the advance of the agricultural frontier will lead to most species being highly vulnerable. Due to the climate and land-use, effects showed different interactions in each country, conservation strategies should be implemented at transboundary and national levels. Keywords: Climate changes. Edaphic variables. Habitat loss. Rarity. Richness patterns. Species distribution models

Análise do comportamento espaço-temporal do fogo em formações campestres do Bioma Mata Atlântica no estado do Rio Grande do Sul

Avaliar o impacto do fogo em formações campestres requer uma compreensão das relações ambientais e antrópicas sobre a dinâmica da paisagem ao longo do tempo. Nos campos de altitude situados no sul do Brasil, o fogo tem sido um componente intrínseco da ecologia dos ecossistemas, afetando as políticas públicas, econômicas, sociais e até mesmo culturais das interações do homem com a natureza. O objetivo deste estudo foi analisar espacial e temporalmente o efeito do uso do fogo em formações campestres do Bioma Mata Atlântica (BMA) no estado do Rio Grande do Sul (RS) usando técnicas de sensoriamento remoto (RS). Para isso, este estudo foi dividido em quatro artigos com diferentes abordagens metodológicas: i) Aplicação do método do Itens de Relatório Preferidos para Revisões Sistemáticas e Meta-Análise (PRISMA) utilizando o software VOSviewer para analisar o estado da arte de como o Sensoriamento Remoto (SR) vem sendo aplicado para a análise de fogo em formações campestres; ii) Identificação da influência de variáveis ambientais e antropogênicas na ocorrência de focos de fogo e a sua resposta às mudanças do forçamento radiativo derivadas de cenários climáticos futuros utilizando o algoritmo RandomForest; iii) Identificação da frequência e distribuição de áreas queimadas para avaliar as ferramentas de gestão pública para controle do uso do fogo utilizando bandas espectrais e o índice ΔNBR na plataforma Google Earth Engine (GEE), assim como a análise da aplicabilidade do produto MapBiomas Fogo para os campos de altitude; e iv) Aplicação do Índice de Degradação de Campo (IDC) para avaliar o grau de degradação de formações campestre e sua sensibilidade ao manejo com fogo. Os resultados apresentados em cada artigo permitirem a inferência das interações do fogo, clima, uso da terra e vegetação, além de contribuir para a avaliação da eficiência das áreas protegidas e das políticas públicas para a conservação desses ecossistemas diante das mudanças climáticas globais.To assess the impact of fire on grasslands, it is necessary to comprehend the environmental and anthropogenic relationships of landscape dynamics over time. In the highlands of southern Brazil, fire has been an integral part of ecosystem ecology, influencing public, economic, social, and cultural policies of human interactions with nature. This study aims to analyze the effects of fire on grasslands of the Atlantic Forest Biome (BMA) in Rio Grande do Sul (RS) using remote sensing (RS) techniques. The study is divided into four articles, each with a distinct methodological approach. i) The Preferred Report Items method for Systematic Reviews and Meta-Analysis (PRISMA) was applied using the VOSviewer software to analyze the state of the art of how Remote Sensing (SR) has been utilized for analyzing fire in grasslands. II) The study identified the impact of environmental and anthropogenic variables on fire occurrence and their response to changes in radiative forcing using the RandomForest algorithm. Iii) The study identified the frequency and distribution of burned areas to evaluate public management tools for controlling fire using spectral bands and the ΔNBR index on the Google Earth Engine (GEE) platform, and the applicability of the MapBiomas Fogo product for the highland grasslands. iv) The Grassland Degradation Index (IDC) was applied to assess the degree of degradation of grasslands and their sensitivity to fire management. The results of each article contribute to understanding the interactions of fire, climate, land use, and vegetation and the evaluation of the efficiency of protected areas and public policies for the conservation of these ecosystems in the face of global climate change