Factors affecting savanna and forest regeneration in pastures across the cerrado.

The Cerrado region comprises the world's most biodiverse savanna and the largest cultivated pastures for cattle in Brazil. Forty percent of these pastures are unproductive or degraded, with bare soil and native vegetation increasingly replacing exotic forage grasses. This study sought to investigate the regeneration of native vegetation in the pastures of the Cerrado and to evaluate the contribution of biophysical, land management, and landscape attributes to this process. Across the Cerrado, we analyzed pasture plant communities and the attributes of pasture management intensification, fire events, landscape native vegetation cover, and climate and soil types of 93 active pastures and 15 abandoned pastures. For the abandoned pastures, time since abandonment was an additional variable. On actively cultivated pastures, savanna regeneration varied from 0 to 70%, with a diversity of herbs and woody species. Pasture management was the main predictor of savanna regeneration on cultivated pastures. On abandoned pastures, time since abandonment was the main predictor. Exotic grass cover had a strong negative relationship with savanna regeneration and they were present even in pastures abandoned for 44 years. Our study reveals the potential of natural regeneration of the Cerrado and its particular predictors. The occurrence of pastures with high natural regeneration indicates that national policies can promote native vegetation restoration and silvopastoral systems with predictable, low cost implementation.

Mapping the regeneration potential of native vegetation in cultivated pastures of the Brazilian Cerrado.

The Brazilian Cerrado is a hotspot of biodiversity conservation and an important global agricultural region. Cultivated pastures under different degradation levels are dominant in the landscape and are being targeted for sustainable agricultural intensification and restoration of native vegetation. In this study, we classified the cultivated pastures of the Brazilian Cerrado according to their potential for natural regeneration, based on field surveys and environmental predictors. We surveyed the native vegetation cover in 186 plots distributed along 93 cultivated pastures. The environmental predictors considered in this study were the proportion of sand in the soil, cation exchange capacity, climate water deficit, pasture age, slope, and pasture vigor index. We then applied the Random Forest regression algorithm to predict and map the cultivated pastures according to their potential for natural regeneration in the 19 Cerrado ecoregions. The potential for natural regeneration was classified into low (< 30% of native plant cover), medium (30-50%), and high (> 50%). Our prediction explained 75% of the data variability. Most of the cultivated pastures presented medium potential for natural regeneration (57%), while 31% and 12% presented high and low potentials, respectively. Cultivated pastures in ecoregions with high mechanization, due to their high water availability and extensive flat terrains, presented low potential for natural regeneration. This first attempt to map the potential for natural regeneration in the cultivated pastures of the Brazilian Cerrado can be used as a proxy for planning low-cost and predictable restoration or environmentally sustainable intensification in this major type of land use found in this biome.

Conformity of the NASADEM_HGT and ALOS AW3D30 DEM with the Altitude from the Brazilian Geodetic Reference Stations: A Case Study from Brazilian Cerrado.

The Brazilian Cerrado (tropical savanna) is the second largest biome in South America and the main region in the country for agricultural production. Altitude is crucial information for decision-makers and planners since it is directly related to temperature that conditions, for example, the climatic risk of rainfed crop plantations. This study analyzes the conformity of two freely available digital elevation models (DEMs), the NASADEM Merged Digital Elevation Model Global 1 arc second (NASADEM_HGT) version 1 and the Advanced Land Observing Satellite Global Digital Surface Model (ALOS AW3D30), version 3.1, with the altitudes provided by 1695 reference stations of the Brazilian Geodetic System. Both models were evaluated based on the parameters recommended in the Brazilian Cartographic Accuracy Standard for Digital Cartographic Products (PEC-PCD), which defines error tolerances according to eight different scales (from 1:1000 to 1:250,000) and classes A (most strict tolerance, for example, 0.17 m for 1:1000 scale), B, C, and D (least strict tolerance, for example, 50 m for 1:250,000 scale). Considering the class A, the NASADEM_HGT meets 1:250,000 and lower scales, while AW3D30 meets 1:100,000 and lower scales; for class B, NASADEM_HGT meets 1:100,000 scale and AW3D30 meets 1:50,000. AW3D30 presented lower values of root mean square error, standard deviation, and bias, indicating that it presents higher accuracy in relation to the NASADEM_HGT. Within eight of Cerrado's municipalities with the highest grain production, the differences between average altitudes, measured by the Cohen's effect size, were statistically insignificant. The results obtained by the PEC-PCD for the Cerrado biome indicate that both models can be employed in different DEM-dependent applications over this biome.

Spatial distribution of soil δ13C in the central Brazilian savanna.

Stable carbon isotope ratios (δ13C) of soil record information regarding C3 and C4 plants at the landscape scale that can be used to document vegetation distribution patterns. The Central Brazilian savanna (locally called the Cerrado) has a substantial potential to develop studies of patterns of dynamics and distribution of soil δ13C, due to its environmental diversity. The purpose of this work was to develop a spatial model of soil δ13C (soil δ13C isoscape) to the Cerrado, based on multiple linear regression analysis, and compare the results with the existing model to obtain greater detail of the soil δ13C distribution. The model used 219 soil samples (0-20 cm depth) and a set of climatic, pedological, topographic, and vegetation correlations. The soil δ13C isoscape model presented amplitude between -29‰ and -13‰, with the highest estimated values in the southern and the lowest values in the northern of the Cerrado. Results indicate that soil δ13C, by reflecting the relative contribution of C3 and C4 species to plant community productivity, served as a proxy indicator of the vegetation history at the landscape scale for the Central Brazilian savanna. Despite the large sampling effort, there are still regions with some gaps that the model could not estimate. However, the soil δ13C isoscape model filled most the existing gaps and provided greater detail of some unique local aspects of the Cerrado.

Large-scale Degradation of the Tocantins-Araguaia River Basin.

The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations.

Cerrado ecoregions: A spatial framework to assess and prioritize Brazilian savanna environmental diversity for conservation.

The Brazilian Cerrado is the second largest biome in Latin America, extending over more than 200 million ha and hosts some of the most intensive agricultural activities for grain and beef production in the world. Because of the biodiversity richness and high levels of endemism, Cerrado is considered one of world's hotspot for biodiversity conservation. The objectives of this study are three-fold: to present a comprehensive division of Cerrado into different ecoregions that reflect the environmental heterogeneity within the biome; to analyze the ecoregions in terms of biophysical characteristics, protected areas, environmental liability in riparian permanent protection areas along watercourses, and priorities for biodiversity conservation; and to rank the ecoregions in terms of endangerment for biodiversity conservation and restoration. A previous study that delineated 22 ecoregions using geomorphology, vegetation, soil, geology, and plant diversity maps was revised using topography, vegetation, precipitation, and soil maps. Our new ecoregion map consists of 19 units that are unique in terms of landscape characteristics and has been adjusted to the current official boundary map of Cerrado. Some of the ecoregions consist of only one geomorphological compartment, whereas others are heterogeneous, consisting of up to eight compartments. Ferralsols comprise the dominant soil type in 14 of the ecoregions. The percentage of protected areas within ecoregions ranges from 1.7% to 51.5%. The most endangered ecoregion, where land use change critically threatens habitat integrity, is the Depressão Cárstica do São Francisco (states of Bahia, Minas Gerais, and Piauí), where environmental liability along riparian permanent protection areas amounts to 85.6% of the total area. Our proposed ecoregion map provides a spatial framework for regional and local assessments to improve decision-making processes to reconcile conservation and restoration planning, sustainable agriculture, and provision of ecosystem services. Besides de adjustment of the previous Cerrado's ecoregion map to the official biome boundary (relevant for the implementation of public policies of conservation as those regulated by the Brazilian Forest Code), the new analyses of the ecoregion map represent a substantial improvement in comparison to the ones conducted by the previous study in 2003. In addition, current web resources allow us to make all the information used or derived from this study available to other users. This opens the possibility of additional improvements of our findings by the scientific community or to be used effectively by decision makers.

The spectral changes of deforestation in the Brazilian tropical savanna.

The Cerrado is a biome in Brazil that is experiencing the most rapid loss in natural vegetation. The objective of this study was to analyze the changes in the spectral response in the red, near infrared (NIR), middle infrared (MIR), and normalized difference vegetation index (NDVI) when native vegetation in the Cerrado is deforested. The test sites were regions of the Cerrado located in the states of Bahia, Minas Gerais, and Mato Grosso. For each region, a pair of Landsat Thematic Mapper (TM) scenes from 2008 (before deforestation) and 2009 (after deforestation) was compared. A set of 1,380 samples of deforested polygons and an equal number of samples of native vegetation have their spectral properties statistically analyzed. The accuracy of deforestation detections was also evaluated using high spatial resolution imagery. Results showed that the spectral data of deforested areas and their corresponding native vegetation were statistically different. The red band showed the highest difference between the reflectance data from deforested areas and native vegetation, while the NIR band showed the lowest difference. A consistent pattern of spectral change when native vegetation in the Cerrado is deforested was identified regardless of the location in the biome. The overall accuracy of deforestation detections was 97.75%. Considering both the marked pattern of spectral changes and the high deforestation detection accuracy, this study suggests that deforestation in Cerrado can be accurately monitored, but a strong seasonal and spatial variability of spectral changes might be expected.

A classification of cultivated pastures in the Brazilian Cerrado for sustainable intensification and savanna restoration.

The Brazilian Cerrado, with over 200 million hectares, has approximately 28% of its area occupied by cultivated pasturelands and 39% of them are degraded. In this study, we propose a new classification of the Cerrado pastures and recommendations for sustainable intensification and savanna restoration. We propose seven classes of pastures based on the ground cover proportions of exotic grass, bare soil, and native vegetation. These lands need to be acknowledged for their biodiversity conservation and potential for sustainable intensification and restoration. In order to make ecological intensification available for the ranchers, research and technology transfer have to embrace native tree species-based silviculture, native-grass-based forage management and enhancement, and value chain of biodiversity-friendly products. The pasture management proposals of this paper are based on a concept of biodiversity as an ecosystem service, promoting local productivity and global ecosystem services.

Data for: Terrain units, land use/cover, and gross primary productivity of the largest fluvial basin in the Brazilian Amazonia/Cerrado ecotone: The Araguaia River Basin.

Integrity of most of tropical wetlands is threatened because they are often considered freely available resources of land and water. The Araguaia River Basin is one of the Brazilian basins most influenced by tropical seasonal floods, in addition to being rich in biodiversity and providing diverse ecosystem services. Here, we propose the analysis of the landscape of Araguaia Basin in terms of terrain units, rainfall, land use/cover and gross primary productivity (GPP). For this, the integration of different databases was made, including the topographic domains, protected areas and indigenous lands; land use/cover map (year 2016); time series of GPP derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor (period of 2000-2015); Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM); and precipitation data produced by the WorldClim version 2 dataset. GPP time serie were processed using statistical methods of decomposition throughout R software. The proposed methodology can assist in new studies aimed at land use changes and carbon cycles.

Land cover mapping of the tropical savanna region in Brazil.

The Brazilian tropical savanna (Cerrado), encompassing more than 204 million hectares in the central part of the country, is the second richest biome in Brazil in terms of biodiversity and presents high land use pressure. The objective of this study was to map the land cover of the Cerrado biome based on the segmentation and visual interpretation of 170 Landsat Enhanced Thematic Mapper Plus satellite scenes acquired in 2002. The following land cover classes were discriminated: grasslands, shrublands, forestlands, croplands, pasturelands, reforestations, urban areas, and mining areas. The results showed that the remnant natural vegetation is still covering about 61% of the biome, however, on a highly asymmetrical basis. While natural physiognomies comprise 90% of the northern part of the biome, only 15% are left in its southern portions. Shrublands were the dominant natural land cover class, while pasturelands were the dominant land use class in the Cerrado biome. The final Cerrado's land cover map confirmed the intensive land use pressure in this unique biome. This paper also showed that Landsat-like sensors can provide feasible land cover maps of Cerrado, although ancillary data are required to help image interpretation.

Abordagem metodológica baseada em imagens do SAR-R99B para identificar prováveis pistas de pouso não-homologadas na Amazônia

This study presents a methodological approach based on radar images and on gray level, size and geometric pattern to identify potential unofficial airplane strips in Amazonia. The following procedures were conducted: georeferencing of a L-band, HH polarization, 3-meter spatial resolution image obtained by the SAR-R99B system over the Itaituba municipality, State of Para; subtraction of speckle noise with a median filter; image classification with the ISODATA unsupervised technique; conversion of selected targets of interest into vector format; and calculation and automatic selection of targets of interest by the circularity and tortuosity indices. Among the 10 previously identified targets, two were considered as potential unofficial airplane strips by the above mentioned indices.

Este estudo apresenta uma abordagem metodológica baseada em imagens de radar e nos critérios de tonalidade, tamanho e forma geométrica para identificar prováveis pistas de pouso não-homologadas na Amazônia. Os seguintes procedimentos foram conduzidos: georreferenciamento da imagem do sensor SAR-R99B do município paraense de Itaituba, adquirida na banda L, polarização HH e resolução espacial de três metros; subtração do ruído speckle com filtro mediana; classificação com a técnica não-supervisionada ISODATA; vetorização da classe indicativa dos alvos de interesse; e cálculo e seleção automática dos alvos de interesse por critérios de índice de circularidade e de tortuosidade. Foram identificados dez alvos, dos quais dois foram considerados como prováveis pistas de pouso pelos referidos índices.

Técnicas avançadas de sensoriamento remoto aplicadas ao estudo de mudanças climáticas e ao funcionamento dos ecossistemas amazônicos / Advanced remote sensing techniques for global changes and Amazon ecosystem functioning studies

Este artigo se propõe a apresentar exemplos de questões científicas que puderam ser respondidas no contexto do Projeto LBA (Large Sale Biosphere-Atmosphere Experiment in Amazonia) graças à contribuição de informações derivadas de sensoriamento remoto. Os métodos de sensoriamento remoto permitem integrar informações sobre os vários processos físicos e biológicos em diferentes escalas de tempo e espaço. Nesse artigo, são enfatizados aqueles avanços de conhecimento que jamais seriam alcançados sem a concorrência da informação derivada de sensoriamento.