In the southwest United States, the current prolonged warm drought is similar to the predicted future climate change scenarios for the region. This study aimed to determine patterns in vegetation response to the early 21st century drought across multiple biomes. We hypothesized that different biomes (forests, shrublands, and grasslands) would have different relative sensitivities to both climate drivers (precipitation and temperature) and legacy effects (previous-year's productivity). We tested this hypothesis at eight Ameriflux sites in various Southwest biomes using NASA Moderate-resolution Imaging Spectroradiometer Enhanced Vegetation Index (EVI) from 2001 to 2013. All sites experienced prolonged dry conditions during the study period. The impact of combined precipitation and temperature on Southwest ecosystems at both annual and sub-annual timescales was tested using Standardized Precipitation Evapotranspiration Index (SPEI). All biomes studied had critical sub-annual climate periods during which precipitation and temperature influenced production. In forests, annual peak greenness (EVImax) was best predicted by 9-month SPEI calculated in July (i.e., January-July). In shrublands and grasslands, EVImax was best predicted by SPEI in July through September, with little effect of the previous year's EVImax. Daily gross ecosystem production (GEP) derived from flux tower data yielded further insights into the complex interplay between precipitation and temperature. In forests, GEP was driven by cool-season precipitation and constrained by warm-season maximum temperature. GEP in both shrublands and grasslands was driven by summer precipitation and constrained by high daily summer maximum temperatures. In grasslands, there was a negative relationship between temperature and GEP in July, but no relationship in August and September. Consideration of sub-annual climate conditions and the inclusion of the effect of temperature on the water balance allowed us to generalize the functional responses of vegetation to predicted future climate conditions. We conclude that across biomes, drought conditions during critical sub-annual climate periods could have a strong negative impact on vegetation production in the southwestern United States.

Global climate change is predicted to affect environmental systems at the midlatitudes, but the scope, severity, and outcomes of these impacts are yet to be fully understood. This study focuses on the implications of short-term climate variability for forests in central Kentucky. Using a Normalized Difference Vegetation Index (NDVI) calculated from MODerate-Resolution Imaging Spectroradiometer (MODIS) instrument data, the photosynthetic activity of vegetation at Mammoth Cave National Park (MACA) is tracked from 2000 to 2013. Three methods were employed to examine the changes and climate influences in vegetation over the study period: 1) aggregating the NDVI of the Park by year and by summer months (June, July, and August) and examining how these productivity trends could be influenced by precipitation and temperature fluctuations, 2) examining the trend of the NDVI at selected dates throughout the study period to detect phenological shifts around leaf-out and leaf-off, and 3) using a generalized vegetation classification of MACA to clip the imagery based on areas of similar vegetation and then testing correlations between those subsets and teleconnections. The results from the aggregated NDVI show there is an insignificant negative trend. A negative relationship between summer forest productivity at MACA and temperature was found, though more data are needed to rigorously validate this result. Changes in phenology indicate forest productivity is decreasing earlier each year throughout the study period. Finally, the Multivariate ENSO Index and the Pacific Decadal Oscillation index are shown to have significant positive correlations with the summer productivity of MACA during the study period.

In the terrestrial biosphere forests have a significant role as a carbon sink. Under recent climate change, it is increasingly important to detect seasonal change or ‘phenology’ that can influence the global carbon cycle. Monitoring canopies using camera systems has offered an inexpensive means to quantify the phenological changes. However, the reliability is not well known. In order to examine the usefulness of cameras to observe forest phenology, we analysed canopy images taken in two deciduous forests in Japan and England and investigate which colour index is best for tracking forest phenology and predict carbon uptake by trees. A camera test using model leaves under controlled conditions has also carried out to examine sensitivity of colour indices for discriminating leaf colours. The main findings of the present study are: 1) Time courses of colour indices derived from images taken in deciduous forests showed typical patterns throughout the growing season. Although cameras are not calibrated instrument, analysis of images allowed detecting the timings of phenological events such as leaf onset and leaf fall; 2) The strength of the green channel (or chromatic coordinate of green) was useful to observe leaf expansion as well as damage by spring late frost. However, the results of the camera test using model leaves suggested that this index was not sufficiently sensitive to detect leaf senescence. Amongst colour indices, Hue was the most robust metric for different cameras, different atmospheric conditions and different distances. The test also revealed Hue was useful to track nitrogen status of leaves; 3) Modelling results using a light use efficiency model for GPP showed a strong relationship between GPP and Hue, which was stronger than the relationships using alternative traditional indices.

A quantificação de biomassa e carbono em florestas requer a aplicação de métodos adequados para se obter estimativas confiáveis de seus estoques. Neste sentido, o objetivo deste trabalho foi avaliar a aplicação de alguns métodos utilizados para a predição e estimação dessas variáveis em florestas nativas e restauradas da Mata Atlântica. Para isso, um primeiro capítulo aborda o uso do índice de vegetação NDVI como ferramenta auxiliar no inventário de estoques de biomassa em áreas de restauração florestal. Diferentes métodos de amostragem foram comparados em termos de precisão e conservadorismo das estimativas. Os resultados demonstraram que o NDVI apresentou adequada correlação com a biomassa estimada nas parcelas do inventário florestal instaladas em campo, sendo viável sua aplicação, seja para auxiliar na determinação de estratos, na aplicação da amostragem estratificada, seja como variável suplementar na utilização de um estimador de regressão relacionando-o à biomassa, no procedimento da amostragem dupla. Este último método, possibilitou minimizar as incertezas acerca das estimativas, valendo-se de uma intensidade amostral reduzida, fato que torna seu uso interessante, principalmente aos estudos em escala ampla, de modo a aumentar a confiabilidade das quantificações de estoques de carbono presentes na biomassa florestal, a custos de inventário reduzido. Um segundo capítulo discute a abordagem metodológica utilizada para inferir sobre a qualidade de modelos preditivos quando da seleção de modelos concorrentes para a aplicação em estudos de biomassa de florestas nativas. Para tanto, seis modelos considerando diferentes combinações de variáveis preditoras, incluindo diâmetro, altura total e alguma informação relativa à densidade da madeira, foram construídos a partir de dados de uma amostra de 80 árvores. As equações de predição de biomassa seca geradas por estes modelos foram avaliadas quanto à sua qualidade de ajuste e desempenho de aplicação. Neste segundo caso, aplicando-as aos dados de outra amostra composta por 146 árvores presentes em nove parcelas destrutivas instaladas em diferentes estágios sucessionais da floresta, de modo a possibilitar a avaliação dos vieses preditivos. No intuito de se verificar as discrepâncias nas estimativas de biomassa devido à aplicação das diferentes equações de predição de biomassa, as equações desenvolvidas, junto a outras disponíveis na literatura, foram aplicados aos dados de um inventário florestal realizado na área estudada. O estudo confirma a natureza empírica destas equações, atentando para a necessidade de prévia avaliação de seu desempenho de predição antes de sua aplicação, em especial, das ajustadas com amostras de outras florestas, expondo alguns dos principais fatores associados às causas de incertezas nas quantificações dos estoques de biomassa nos estudos realizado em florestas nativas. / The biomass and carbon quantification requires the application of appropriate methods to obtain reliable estimates of their stocks in natural and planted forests. The aim of this study was to evaluate different applicable methods to estimate biomass in both, natural and restored Atlantic Forests. The first chapter discusses the use of the vegetation index (NDVI) as an auxiliary tool in the inventory of biomass stocks in forest restoration areas. Different sampling methods were compared in terms of its accuracy and conservativeness. The results shown an adequate correlation between the vegetation index and the measured biomass, making the NDVI applicable either as supporting decision tool to define strata in the stratified sampling or as a predictor in the double sampling procedure. The last method allowed to the minimization of the uncertainties related to the biomass estimation combined to the reduction of sampling efforts. It makes the approach very interesting, especially in the context of large-scale surveys. The second chapter discusses the methodological approach used to evaluate the quality of predictive models applied to biomass studies in natural forests. For this, six models were fitted from 80 sample trees, using different combinations of predictor variables, such as, total height and information of wood density. The predictive equations generated by the models were evaluated according to their quality of fit and prediction performance. In order to evaluate its prediction performance, the equations were applied to the dataset of another 146 sample trees measured in nine destructive sample plots. The plots were located in different forest successional stages allowing the evaluation of model predictive bias among the stages. A third step of the analysis was the application of literature equations to a dataset of a forest inventory conducted in the study area, in order to verify the discrepancies in the estimates due to the use of these different models. The study confirms the empirical nature of the biomass equations and the need of previous evaluation in terms of prediction performance. This conclusion is even more relevant when we consider the equations that were obtained from other forests types, exposing some of the key factors associated to the causes of uncertainty in the biomass estimation applied to natural forests.

A fertilização da cana-de-açúcar com nitrogênio (N), embora intensamente estudada, ainda representa desafio aos produtores e pesquisadores, principalmente devido à alta variabilidade de resposta dessa cultura ao N aplicado. Visando melhorar a eficiência das adubações, a aplicação de fertilizantes em doses variáveis é indispensável. Nesse contexto, sensores que mensuram a refletância do dossel apresentam-se como alternativa interessante. Bons resultados com essa tecnologia vêm sendo observado para as culturas de trigo e milho. Entretanto, apesar da efetividade desses sensores em identificar alguns parâmetros da canade- açúcar, ainda há várias incógnitas quanto a seu uso, principalmente em relação à forma de converter as leituras desse equipamento em uma dose de N a ser aplicada nos canaviais. Desse modo, o objetivo principal dessa tese foi definir uma metodologia capaz de direcionar a aplicação de N em taxas variáveis em cana-de-açúcar a partir de informações obtidas com um sensor de dossel. Para tanto, foi necessário: 1) estabelecer qual o índice de vegetação mais indicado para ser usado em cana, dentre aqueles possíveis de se obter com o sensor de dossel utilizado, e quais os parâmetros da cultura que influenciam nas leituras com o sensor; 2) avaliar a eficácia desse equipamento em identificar a resposta da cultura ao N e a sua relação com a produtividade de colmos; e 3) avaliar se alguma metodologia de recomendação de N estabelecida para outras culturas é viável para direcionar a aplicação de N em cana-de-açúcar. Foram conduzidos experimentos em de parcelas e em forma de faixas da cultura, com aplicação de diferentes doses de N. Todos os experimentos, além de algumas áreas comerciais, foram avaliados com o sensor Crop Circle, modelo ACS-430 (Holland Scientific, Lincoln, NE, EUA), quando a cultura apresentava altura de plantas entre 0,4 e 0,6 m. A canade- açúcar apresentou resposta variável ao N aplicado. Dentre os diferentes índices de vegetação, calculados com as refletâncias mensuradas pelo sensor, os que utilizam a banda situada na região espectral do red edge apresentaram os melhores resultados. O acúmulo de biomassa da parte aérea foi o que mais influenciou as leituras com o sensor de dossel. Devido a isso, o sensor também se mostrou eficiente em estimar a produtividade da cana-de-açúcar. A variabilidade intrínseca de cada área, causada por danos à soqueira e outros fatores limitantes ao desenvolvimento da cana, impede o uso das estratégias de aplicação apontadas na literatura. Contudo, por meio da capacidade do sensor em estimar a produtividade, foi proposto um algoritmo agronômico de fertilização nitrogenada. Essa metodologia direciona maior quantidade de N em regiões com maior vigor da cultura, assumindo que, nessa situação, as plantas apresentam maior probabilidade de absorverem N proveniente do fertilizante. / Sugarcane nitrogen fertilization (N), even being extensively studied, is still a challenge to producers and researchers, mainly due to the high N response variability showed by this crop. For this reason, variable-rate N application is essential. Sensors that measure the crop canopy reflectance are an interesting alternative. Good results with this technology have been found for wheat and corn. However, despite the suitability of these sensors in identifying some sugarcane parameters, there are still many gaps to be answered, especially related to how convert the sensor readings in an N rate to be applied in the fields. Thus, the main objective of this thesis was to develop a method to guide the variable-rate N application in sugarcane, based on canopy sensor readings. To achieve this goal, it was necessary the following studies: 1) establish which is the most appropriate vegetation index to be used in sugarcane fields, among those possible to be obtained from the canopy sensor used, as well as which crop aspects can influence the readings; 2) evaluate the effectiveness of this equipment to identify the crop N response and its relationship with the sugarcane stalk yield; and 3) test some methodologies available in the literature in order to guide the sugarcane N fertilization. Plot and strips experiments with N rates were performed. All the experiments and some producing fields were evaluated, when the crop stem height was between 0.4 and 0.6 m, with the Crop Circle sensor, model ACS-430 (Holland Scientific, Lincoln, NE, USA). The sugarcane showed variable response to the N applied. Among the different vegetation indices calculated from the reflectance obtained by the sensor, the red edge vegetation indices showed the best results. The aboveground biomass was the crop parameter that highest interfered in the canopy sensor readings, indicating that the sensor was effective in estimating the sugarcane yield either. The intrinsic variability of each field, caused by ratoon damage and other limiting factors, prevents the implementation of some strategies pointed out in the literature. However, due to canopy sensor ability for yield estimation, it was proposed an algorithm to guide higher N rates in areas with greater crop vigor, assuming that in this situation is more promising to the plants absorbing N from the fertilizers.

Orientador: Paulo Milton Barbosa Landim / Banca: Ailton Luchiari / Banca: Arlei Benedito Macedo / Banca: Ardemírio Barros Silva / Banca: Juércio Tavares de Mattos / Resumo: O aspecto fundamental do trabalho é mostrar a importância da integração de um Sistema de Informações Geográficas (SIG) com procedimentos geoestatísticos na análise e interpretação de dados distribuídos no tempo e no espaço. A idéia é aplicar uma análise integrada sobre o meio ambiente que melhor caracterize os aspectos físicos com ênfase na variação do índice de vegetação de diferença normalizada (IVDN) do ano 1989 para o ano 1997. O propósito é também realizar a caracterização morfométrica do relevo, principalmente com relação à sua declividade, mapear a concentração e distribuição espacial de metais pesados no solo, obtidos por amostragens georreferenciadas do horizonte Bw (camada do solo com profundidade de até 1m) na área de estudo. A metodologia envolve o uso e a integração de documentos cartográficos, tais como mapas topográficos, fotografias aéreas, imagens de satélite e levantamento de campo, cada qual direcionado a uma representação espacial, utilizando-se para sua manipulação de um Sistema de Informações Geográficas (SIG). A proposta é aplicada em uma área pertencente à Baixada Santista, que esta inserida na Carta Topográfica em 1:50.000 do IGG - SP - 1972 FOLHA DE SANTOS. Depois de obtidos os diversos mapas são elaborados estudos de regressão múltipla espacial, os quais demonstram correlações significativas entre as variáveis "metais pesados" e "declividade" na mudança dos índices de vegetação para os anos de 1989 e 1997. / Abstract: The basic approach of the work is to show the importance of the integration of a Geographic Information System (GIS) with geostatístics procedures in the analysis and interpretation of data distributed in time and space. The idea is to apply an environment integrated analysis that better characterizes the geographic landscape with emphasis in the variation of the Normalized Difference Vegetation Index (NDVI) during the years of 1989 to 1997. The purpose is also understand the morphometric characterization of the relief, mainly regarding its slope, mapping concentration and space distribution of heavy metals in the ground, obtained by sampling of the Bw horizon (layer of the ground with depth until 1m), in the study area. The methodology involves the use and the integration of cartographic documents, such as topographical maps, air photographs, satellite images and field survey, each one directed to a space representation of the studied event and manipulated by a Geographic Information System. The proposal study is applied in an area pertaining to the "Baixada Santista" that is inserted in the 1:50,000 Topographical Chart of the Institute of Geophysics and Geology (IGG) SP. 1972 "Folha de Santos". After obtained the diverse maps multiple regression analysis had been elaborated, which demonstrated the significant correlation between changeable heavy metals and slope controlling the vegetation indices change during the studied period of time. / Doutor

Submitted by José Carlos Toledo Veniziani Junior (veniziani@gmail.com) on 2018-05-30T10:46:24Z No. of bitstreams: 1 Veniziani_Jr_J_C_T.pdf: 11360032 bytes, checksum: c6b48273852e5aad2d73183ee856e5ec (MD5) / Approved for entry into archive by Adriana Aparecida Puerta null (dripuerta@rc.unesp.br) on 2018-05-30T13:15:02Z (GMT) No. of bitstreams: 1 venizianijunior_jct_dr_rcla.pdf: 10933461 bytes, checksum: 13254f5586b981ff360e18d863f2ad6d (MD5) / Made available in DSpace on 2018-05-30T13:15:02Z (GMT). No. of bitstreams: 1 venizianijunior_jct_dr_rcla.pdf: 10933461 bytes, checksum: 13254f5586b981ff360e18d863f2ad6d (MD5) Previous issue date: 2018-04-13 / A disponibilidade da água é influenciada pelo comportamento sistêmico do ciclo hidrológico, do qual a vazão, a precipitação e a cobertura vegetal são importantes elementos. Devido às suas características espaciais, a bacia hidrográfica constitui uma unidade geográfica adequada para a realização de estudos ambientais e hidrológicos. As ferramentas de geoprocessamento forneceram suporte metodológico à realização destes estudos, facilitando a obtenção, a organização e a análise espacial. Esta tese analisou a relação entre as variáveis vazão, precipitação, e a densidade da cobertura vegetal, estimada através do índice de vegetação da diferença normalizada, (IVDN), para as sub-bacias hidrográficas dos rios Jacaré-Pepira e Jaú (SP). Também objetivou verificar a viabilidade do uso do IVDN como subsídio à gestão ambiental de bacias hidrográficas. Os resultados mostraram que existe correlação entre as variáveis precipitação, vazão e o IVDN, utilizado como um indicativo das características da cobertura vegetal. Esses resultados indicaram que as vazões médias e mínimas apresentaram maior correlação com o IVDN. Considerando os anos padrão climáticos, secos, chuvosos e habituais, foi possível perceber que nos anos secos esta correlação ficou mais evidente reforçando a compreensão de que maiores densidades de cobertura vegetal aumentam a infiltração e reduzem o escoamento superficial, garantindo uma maior disponibilidade de água para as demandas socioambientais locais. A dinâmica espaço-temporal do uso e ocupação das terras na bacia do Jacaré-Pepira era menos intensa e caracterizada principalmente por pastagens e silvicultura que não demandam ciclos de cultivo curtos. Enquanto que na Bacia do Rio Jaú a dinâmica era mais intensa, sobretudo por influência do cultivo de cana de açúcar que apresenta ciclos curtos de plantio e colheita. A precipitação e IVDN apresentaram dependência espacial na sub-bacia do rio Jacaré-Pepira, enquanto no rio Jaú esta dependência não foi verificada. Isto se deve ao fato de que a cobertura vegetal suprimida no período da colheita, não ser influenciada diretamente pelas precipitações, diminuindo a dependência espacial destas duas variáveis. Foi possível verificar que o IVDN representa um importante indicador da situação ambiental hidrológica local, podendo subsidiar a gestão ambiental de bacias hidrográficas. Essas constatações são importantes para a gestão dos recursos hídricos superficiais em bacias hidrográficas, evidenciando o impacto do uso das terras na cobertura vegetal e na vazão, interferindo diretamente na disponibilidade da água superficial para a sociedade. / The systemic behavior of the hydrological cycle, mainly flow, precipitation and vegetation cover influence the availability of water. The watershed is the appropriate geographic unit for environmental and hydrological studies. Geographic Information Systems (GIS), and remote sensing, helping to carry out hydrological studies, making it easier to obtain, organize, and analyze data. The objective of this research was to characterize the main environmental aspects and analyze the relation among flow rate, rainfall, and the vegetation cover variables, estimated by the normalized difference vegetation index (NDVI), for the sub-basins of the Jacaré-Pepira and Jaú rivers (SP). It was also possible to check the viability to use NDVI to manage the environmental conditions of watershed. These results indicated that the average and minimum flows are the variables that showed the highest correlation with the NDVI in both areas. In the dry standard years, the correlation between the IVDN and the flow were more evident. This situation showed that greater intensities of vegetal cover intensify the infiltration and reduce the surface runoff, offering a greater availability of water for the local socio-environmental processes. The dynamics of land use in Jacaré-Pepira was less intense and characterized mainly by pasture and silviculture that do not require short crop cycles. While in Jaú the dynamics were more intense, mainly to the influence of sugarcane cultivation, which presents short crop cycles. The variables precipitation and NDVI showed spatial dependence in the Jacaré-Pepira, while in Jaú the dependence was not present. This situation evidenced that the rainfall spatial distribution demonstrated by the coefficient of variation promotes greater impacts in areas where the dynamics of land use is more intense. This situation occurs because the suppressed vegetation in the harvest, by the anthropic action, is not influenced directly by the rains, reducing the spatial dependence of these two variables. The NDVI can be considered an important indicator of the local hydrological environmental situation and subsidize the environmental management of watersheds. It is important for the management of surface water resources, showing how land use and its consequent impact on vegetation cover can influence flow rate, and interfere in the accessibility of surface water to society.

Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-03-03T14:31:40Z No. of bitstreams: 2 Dissertação - Rodrigo Moura Pereira - 2015.pdf: 1322504 bytes, checksum: 556731a5041f0e932f32f21043aecae6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-03-03T15:32:24Z (GMT) No. of bitstreams: 2 Dissertação - Rodrigo Moura Pereira - 2015.pdf: 1322504 bytes, checksum: 556731a5041f0e932f32f21043aecae6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-03-03T15:32:24Z (GMT). No. of bitstreams: 2 Dissertação - Rodrigo Moura Pereira - 2015.pdf: 1322504 bytes, checksum: 556731a5041f0e932f32f21043aecae6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-06-03 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Spectral information obtained by satellite imagery is well related to agronomic variables and can be used to monitor sugarcane growth and their responses to changes in environmental conditions of cultivation in large areas. This study is aimed to establish relationships between orbital data in the spectral ranges of the thermal and active photosynthetic radiation of Landsat-8 satellite with data observed with the leaf area index field (LAI), plant height, number of green leaves, and leaf temperature in plots planted with sugarcane, CTC-04 genotype, in a production cycle in sugarcane plant stage in Santo Antônio de Goiás-GO in the 2013/14 crop year. The first study aimed to calibrate a model to measure the temporal variation of the sugarcane LAI from the Normalized Difference Vegetation Index (NDVI) obtained from satellite Landsat 8’s surface reflectance images. It was conducted and the correlation between the LAI collected in the field and the NDVI with and without application of atmospheric correction. The corrected model showed the best relationship with field data. The application of the spectral model was efficient to monitor LAI over a sugarcane plant cycle. The results suggest that the NDVI-LAI relationship may vary during the production cycle of sugarcane due to variations in growth, development, and environmental conditions. Spectral variable NDVI with atmospheric correction was highly correlated (R² = 0,83) with LAI but the relationship proved to be affected by the NDVI saturation point at high values of LAI observed in the field. The second study aimed to evaluate the applicability of surface temperature (LST) obtained from the thermal bands of the Landsat-8 in correlation with the leaf temperature of sugarcane, to establish relationships able to detect water stress remotely through the images, in the occurrence period of drought throughout the year production in rain fed crop in the Cerrado region. The results showed that LST, despite having low direct association with the leaf temperature, has the potential of monitoring water stress in sugarcane within the Cerrado region, since the simulation of the difference between LST and the air temperature accompanies the spread between the leaf temperature and the air, the dynamics of soil water balance and changes in crop growth rates that occur in response to water stress. / A informação espectral obtida a partir de imagens de satélite possui boa relação com variáveis agronômicas e pode contribuir com informações para o monitoramento do crescimento e de suas respostas em relação a variações das condições ambientais de cultivo em grandes áreas. Dessa forma objetivou-se estabelecer relações entre os dados orbitais nas faixas espectrais da radiação fotossinteticamente ativa e termal do satélite Landsat-8 com dados observados em campo de índice de área foliar (IAF), altura de plantas, número de folhas verdes e temperatura foliar em talhões cultivados com cana-de-açúcar, variedade CTC-04, em um ciclo de produção no estágio de cana-planta no município de Santo Antônio de Goiás-GO na safra 2013/14. O primeiro estudo teve como objetivo calibrar um modelo para medir a variação temporal do IAF da cana-de-açúcar a partir do Índice de Vegetação por Diferença Normalizada (NDVI) obtido a partir de imagens de reflectância de superfície do satélite Landsat 8. Foi realizada a correlação entre o IAF coletado em campo e o NDVI com e sem aplicação de correção atmosférica. O modelo corrigido apresentou a melhor relação com os dados de campo. A aplicação do modelo IAF espectral foi eficiente no acompanhamento do IAF ao longo de um ciclo de cana-planta. Os resultados sugerem que a relação NDVI-IAF pode variar durante o ciclo de produção da cana-de-açúcar em função das variações de crescimento e desenvolvimento, e condições ambientais. As relações lineares se mostraram fortes durante a fase de produção e senescência das folhas (R² = 0,83), entretanto a relação mostrou-se afetada pelo ponto de saturação do NDVI em valores altos de IAF observados em campo. O segundo estudo teve como objetivo avaliar a aplicabilidade da temperatura de superfície (LST) obtida a partir das bandas termais do Landsat-8 na correlação com a temperatura foliar da cultura, com o intuito de estabelecer relações capazes de detectar remotamente por meio de imagens, o estresse hídrico no período de ocorrência do déficit hídrico ao longo do ano de produção em cultivo de sequeiro na região do Cerrado. Os resultados mostraram que a LST, apesar de ter apresentado baixa associação direta com a temperatura foliar, possui potencial no monitoramento do eventual estresse hídrico na cana-de-açúcar na região do Cerrado, uma vez que a simulação do diferencial entre a LST e a temperatura do ar acompanha o diferencial entre a temperatura foliar e a do ar, a dinâmica do balanço de água do solo e as alterações nas taxas de crescimento da cultura que ocorrem em resposta à deficiência hídrica.

<p>The Okavango river flows from southern Angola, through the Kavango region of Namibia and into the Okavango Delta in Botswana. The recent peace in Angola hopefully marks the end of the intense suffering that the peoples of the river basin have endured, and the beginning of sustainable decision-making in the area. Informed decision-making however requires knowledge; and there is a need for, and a lack of knowledge regarding basin-wide land cover (LC) changes, and their causes, during the Angolan civil war in the basin. Furthermore, there is a need for, and a lack of knowledge on how expanding large-scale agriculture and urban growth along the Angola-Namibia border affects the water quality of the river.</p><p>The aim of this study was therefore to develop a remote sensing method applicable to the basin (with scant ground-truth data availability) to carry out a systematic historic study of LC changes during the Angolan civil war, to apply the method to the basin, to relate these changes to major societal trends in the region, and to analyse potential impacts of expanding large-scale agriculture and urban growth on the water quality of the river along the Angola-Namibia border.</p><p>A range of remote sensing methods to study historic LC changes in the basin were tried and evaluated against reference data collected during a field visit in Namibia in October 2005. Eventually, two methods were selected and applied to pre-processed Landsat MSS and ETM+ satellite image mosaics of 1973 and 2001 respectively: 1. a combined unsupervised classification and pattern-recognition change detection method providing quantified and geographically distributed binary LC class change trajectory information and, 2. an NDVI (Normalised Difference Vegetation Index) change detection method providing quantified and geographically distributed continuous information on degrees of change in vegetation vigour. In addition, available documents and people initiated in the basin conditions were consulted in the pursuit of discerning major societal trends that the basin had undergone during the Angolan civil war. Finally, concentrations of nutrients (total phosphorous & total nitrogen), bacteria (faecal coliforms & faecal streptococci), conductivity, total dissolved solids, dissolved oxygen, pH, temperature and Secchi depth were sampled at 11 locations upstream and downstream of large-scale agricultural facilities and an urban area during the aforementioned field visit.</p><p>The nature, extent and geographical distribution of LC changes in the study area during the Angolan civil war were determined. The study area (150 922 km²) was the Angolan and Namibian parts of the basin. The results indicate that the vegetation vigour is dynamic and has decreased overall in the area, perhaps connected with precipitation differences between the years. However while the vigour decreased in the northwest, it increased in the northeast, and on more local scales the pattern was often more complex. With respect to migration out of Angola into Namibia, the LC changes followed expectations of more intense use in Namibia close to the border (0-5 km), but not at some distance (10-20 km), particularly east of Rundu. With respect to urbanisation, expectations of increased human impact locally were observed in e.g. Rundu, Menongue and Cuito Cuanavale. Road deterioration was also observed with Angolan urbanisation but some infrastructures appeared less damaged by the war. Some villages (e.g. Savitangaiala de Môma) seem to have been abandoned during the war so that the vegetation could regenerate, which was expected. But other villages (e.g. Techipeio) have not undergone the same vegetation regeneration suggesting they were not abandoned. The areal extent of large-scale agriculture increased 59% (26 km²) during the war, perhaps as a consequence of population growth. But the expansion was not nearly at par with the population growth of the Kavango region (320%), suggesting that a smaller proportion of the population relied on the large-scale agriculture for their subsistence in 2001 compared with 1973.</p><p>No significant impacts were found from the large-scale agriculture and urbanisation on the water quality during the dry season of 2005. Total phosphorous concentrations (with range: 0.067-0.095 mg l^-1) did vary significantly between locations (p=0.013) but locations upstream and downstream of large-scale agricultural facilities were not significantly different (p=0.5444). Neither did faecal coliforms (range: 23-63 counts per 100ml) nor faecal streptococci (range: 8-33 counts per 100ml) vary significantly between locations (p=0.332 and p=0.354 respectively). Thus the impact of Rundu and the extensive livestock farming along the border were not significant at this time. The Cuito river on the other hand significantly decreased both the conductivity (range: 27.2-49.7 μS cm^-1, p<0.0001) and the total dissolved solid concentration (range: 12.7-23.4 mg l^-1, p<0.0001) of the mainstream of the Okavango during the dry season.</p><p>Land cover changes during the Angolan civil war, contributing causes and effects on water quality were studied in this research effort. Many of the obtained results can be used directly or with further application as a knowledge base for sustainable decision-making and management in the basin. Wisely used by institutions charged with that objective, the information can contribute to sustainable development and the ending of suffering and poverty for the benefit of the peoples of the Okavango and beyond.</p>

The Okavango river flows from southern Angola, through the Kavango region of Namibia and into the Okavango Delta in Botswana. The recent peace in Angola hopefully marks the end of the intense suffering that the peoples of the river basin have endured, and the beginning of sustainable decision-making in the area. Informed decision-making however requires knowledge; and there is a need for, and a lack of knowledge regarding basin-wide land cover (LC) changes, and their causes, during the Angolan civil war in the basin. Furthermore, there is a need for, and a lack of knowledge on how expanding large-scale agriculture and urban growth along the Angola-Namibia border affects the water quality of the river. The aim of this study was therefore to develop a remote sensing method applicable to the basin (with scant ground-truth data availability) to carry out a systematic historic study of LC changes during the Angolan civil war, to apply the method to the basin, to relate these changes to major societal trends in the region, and to analyse potential impacts of expanding large-scale agriculture and urban growth on the water quality of the river along the Angola-Namibia border. A range of remote sensing methods to study historic LC changes in the basin were tried and evaluated against reference data collected during a field visit in Namibia in October 2005. Eventually, two methods were selected and applied to pre-processed Landsat MSS and ETM+ satellite image mosaics of 1973 and 2001 respectively: 1. a combined unsupervised classification and pattern-recognition change detection method providing quantified and geographically distributed binary LC class change trajectory information and, 2. an NDVI (Normalised Difference Vegetation Index) change detection method providing quantified and geographically distributed continuous information on degrees of change in vegetation vigour. In addition, available documents and people initiated in the basin conditions were consulted in the pursuit of discerning major societal trends that the basin had undergone during the Angolan civil war. Finally, concentrations of nutrients (total phosphorous &amp; total nitrogen), bacteria (faecal coliforms &amp; faecal streptococci), conductivity, total dissolved solids, dissolved oxygen, pH, temperature and Secchi depth were sampled at 11 locations upstream and downstream of large-scale agricultural facilities and an urban area during the aforementioned field visit. The nature, extent and geographical distribution of LC changes in the study area during the Angolan civil war were determined. The study area (150 922 km2) was the Angolan and Namibian parts of the basin. The results indicate that the vegetation vigour is dynamic and has decreased overall in the area, perhaps connected with precipitation differences between the years. However while the vigour decreased in the northwest, it increased in the northeast, and on more local scales the pattern was often more complex. With respect to migration out of Angola into Namibia, the LC changes followed expectations of more intense use in Namibia close to the border (0-5 km), but not at some distance (10-20 km), particularly east of Rundu. With respect to urbanisation, expectations of increased human impact locally were observed in e.g. Rundu, Menongue and Cuito Cuanavale. Road deterioration was also observed with Angolan urbanisation but some infrastructures appeared less damaged by the war. Some villages (e.g. Savitangaiala de Môma) seem to have been abandoned during the war so that the vegetation could regenerate, which was expected. But other villages (e.g. Techipeio) have not undergone the same vegetation regeneration suggesting they were not abandoned. The areal extent of large-scale agriculture increased 59% (26 km2) during the war, perhaps as a consequence of population growth. But the expansion was not nearly at par with the population growth of the Kavango region (320%), suggesting that a smaller proportion of the population relied on the large-scale agriculture for their subsistence in 2001 compared with 1973. No significant impacts were found from the large-scale agriculture and urbanisation on the water quality during the dry season of 2005. Total phosphorous concentrations (with range: 0.067-0.095 mg l-1) did vary significantly between locations (p=0.013) but locations upstream and downstream of large-scale agricultural facilities were not significantly different (p=0.5444). Neither did faecal coliforms (range: 23-63 counts per 100ml) nor faecal streptococci (range: 8-33 counts per 100ml) vary significantly between locations (p=0.332 and p=0.354 respectively). Thus the impact of Rundu and the extensive livestock farming along the border were not significant at this time. The Cuito river on the other hand significantly decreased both the conductivity (range: 27.2-49.7 μS cm-1, p&lt;0.0001) and the total dissolved solid concentration (range: 12.7-23.4 mg l-1, p&lt;0.0001) of the mainstream of the Okavango during the dry season. Land cover changes during the Angolan civil war, contributing causes and effects on water quality were studied in this research effort. Many of the obtained results can be used directly or with further application as a knowledge base for sustainable decision-making and management in the basin. Wisely used by institutions charged with that objective, the information can contribute to sustainable development and the ending of suffering and poverty for the benefit of the peoples of the Okavango and beyond.