Abstract We used Sentinel-2 imagery time series to generate a vegetation map for the Northern part of the Antarctica Peninsula and offshore islands, including the South Shetlands. The vegetation cover was identified in the NDVI maximum value composite image. The NDVI values were associated with the occurrence of algae (0.15 – 0.20), lichens (0.20 – 0.50), and mosses (0.50 – 0.80). The vegetation cover distribution map was validated using the literature information. Generating a vegetation map distribution on an annual basis was not possible due to high cloud cover in the Antarctic region, especially in coastal áreas, so optical images from 2016 to 2021 were necessary to map the vegetation distribution in the entire study área. The final map analyzed in association with the weather data shows the occurrence of a microenvironment over the western islands of the Antarctic Peninsula that provided vegetation growth conditions. The Sentinel-2 images with 10m spatial resolution allow the assembly of accurate vegetation distribution maps for the Antarctica Peninsula and Islands, the Google Earth Engine cloud computing being essential to process a large amount of the satellite images necessary for processing these maps.

Abstract The remote sensing techniques must be used to obtain long-term information in remote areas, like the Antarctic continent, to monitor the environmental productivity and its changes. The aim of this work was to analyze the surface reflectance profile patterns for the Antarctic biological soil crusts (algae, lichens, and mosses) in an area of Nelson Island (South Shetland Islands, maritime Antarctic), calculated from Landsat and Sentinel-2 images to identify its similarities and differences due to targets, sensors and acquired date. The surface reflectance values for Antarctic biological soil crusts are similar for those observed for biological soil crusts in other Earth extreme environments, like deserts. In Landsat images, the differences among biological soil crusts surface reflectance were identified at visible and near-infrared wavelengths and for Sentinel-2 images, the differences occur at visible, red-edge and shortwave infrared wavelengths, showing the feasibility of using surface reflectance products to identify these different crusts, despite its inherent pixel spectral mixture. Long-term biophysical parameters from such crusts as retrieved from orbital data is not possible due to very low cloud-free images over the Antarctic, which prevents building a consistent surface reflectance time-series which covers all biological soil crusts growth season.

A clorose variegada dos citros (CVC) - causada por Xylella fastidiosa subsp. pauca, bactéria limitada ao xilema, transmitida por insetos cicadelídeos e por material de propagação - é uma das doenças mais importantes da citricultura brasileira. Na Bahia, segundo maior produtor do Brasil, a CVC está presente desde 1997. Os objetivos deste trabalho foram caracterizar o padrão espacial regional da CVC, estabelecer relações entre as variáveis epidemiológicas e práticas horticulturais e avaliar se as medidas de controle usadas até o momento tem sido efetivas. Uma série de prospecções foi realizada em duas regiões da Bahia (Recôncavo Baiano e Litoral Norte), assim como uma prospecção das práticas horticulturais e de controle da doença associadas aos pomares amostrados. A CVC está restrita à região do Litoral Norte, com maior incidência nos três municípios que fazem fronteira com o Estado de Sergipe. A incidência média nesses municípios seguiu um gradiente, maior no interior e decrescendo em direção ao litoral. A presença e disseminação da CVC foi relacionada ao manejo inadequado de viveiros, uso massivo de variedade copa suscetível, extrema concentração de pomares de laranja doce em municípios de alta incidência e ausência de medidas específicas de controle da doença. O Recôncavo Baiano poderia ser considerado como região livre da CVC pois nenhuma planta sintomática foi encontrada em qualquer das prospecções.

Citrus variegated chlorosis (CVC) is one of the most important diseases for Brazilian citricultureIt is caused by Xylella fastidiosa subsp. pauca, a xylem limited, cycadelid and budwood transmitted bacterium. In Bahia, the second most important citrus region in Brazil, CVC has been present since 1997. Our objectives were to characterize the regional spatial pattern of CVC and to establish a relationship between epidemiological variables and horticultural practices, as well as to evaluate whether control measures used so far have been effective and, based on that, to conceive suitable control measures. A series of surveys were performed in two regions of Bahia State (Recôncavo Baiano and Litoral Norte), along with a survey of horticultural and control practices associated with sampled groves. CVC was restricted to Litoral Norte region, especially to three municipalities along the border between Bahia and Sergipe StatesThe mean CVC incidence in these municipalities followed a gradient, higher in the countryside and decreasing along the coast. Presence and dissemination of CVC was related to poor nursery practices, a massive use of a susceptible orange variety, and an extreme concentration of orange groves in high incidence municipalities, as well as to the absence of specific CVC control. Considering that CVC was not found in Recôncavo Baiano, this region could be considered a "CVC free zone" by the local government.