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No description available.

No description available.

Land use transition in dryland ecosystems is one of the major driving forces to landscape change that directly impacts the welfare of humans. In this study, the support vector machine (SVM) classification algorithm and cross tabulation matrix analysis are used to identify systematic and random processes of change. The magnitude and prevailing signals of land use transitions are assessed taking into account net change and swap change. Moreover, spatiotemporal patterns and the relationship of precipitation and the Normalized Difference Vegetation Index (NDVI) are explored to evaluate landscape degradation. The assessment showed that 44% of net change and about 54% of total change occurred during the study period, with the latter being due to swap change. The conversion of over 39% of woodland to cropland accounts for the existence of the highest loss of valuable ecosystem of the region. The spatial relationship of NDVI and precipitation also showed R2 of below 0.5 over 55% of the landscape with no significant changes in the precipitation trend, thus representing an indicative symptom of land degradation. This in-depth analysis of random and systematic landscape change is crucial for designing policy intervention to halt woodland degradation in this fragile environment.

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.

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.

Cette thèse a pour objectif principal d'établir un diagnostic du fonctionnement hydrologique du bassin béninois du fleuve Niger dans le contexte de la péjoration pluviométrique qui a sévèrement touché l'Afrique depuis la décennie 1970. Pour atteindre cet objectif, cette étude s'est appuyée sur trois grands types de données : météorologiques (pluie, température, humidité relative, évapotranspiration potentielle, évapotranspiration réelle), hydrologiques (écoulement, recharge) et des états de surface (superficie des types d'occupation du sol, NDVI). Elle s'est ordonnée autour de trois grands axes Le premier, consacré à l'étude de la variabilité hydro-climatique sur la période 1955-1992, montre que les déficits pluviométriques des décennies 1970 et 1980 ont été largement amplifiés dans les écoulements de toutes les rivières (Mékrou, Alibori, Sota) du bassin béninois du fleuve Niger. Les déficits d'écoulement représentent cinq ou six fois celui de la pluie (Mékrou, Alibori). Ce même déficit pluviométrique est particulièrement amplifié dans la recharge du sous bassin de la Sota à Coubéri : le déficit de la recharge entre les deux sous périodes 1955-1972 et 1973-1992 représente près de cinq fois celui de la pluie. L'étude a aussi montré le comportement différentiel des grès et du socle : Sur le socle (Mékrou, Alibori), l'écoulement est fortement lié à la pluie, comme le montre la valeur élevée du coefficient de corrélation ; en revanche, sur les grès (sous bassin de la Sota à Coubéri), il est lié à la pluie et à la recharge. Le deuxième axe montre l'efficacité des modèles GR4J et GR2M à simuler les écoulements moyens des sous bassins du Niger au Bénin donnée. Ainsi, par l'analyse du critère de Nash appliqué aux écoulements moyens donne des valeurs satisfaisantes (supérieures à 60 % pour la plupart). On peut donc dire que les modèles GR4J et GR2M présentent une certaine efficacité à simuler les écoulements aux pas de temps journalier et mensuel. Toutefois, les Nash sur les écoulements moyens journaliers avec le modèle GR4J sont largement améliorés au pas de temps mensuel avec le GR2M. Dans les sous bassins de la Mékrou, de l'Alibori et de la Sota à Coubéri, les modèles ont identifié une tendance nette à la baisse du cycle hydrologique. On ne doit toutefois pas négliger les limites des résultats obtenus puisque les tests statistiques utilisés n'ont pas pu identifier une tendance avec les modèles dans le sous bassin de la Sota à Gbassè. Le troisième axe, consacré à l'étude d'impact de la dynamique des états de surface sur les écoulements, montre que les types d'occupation du sol ont connu de grands changements entre 1979 et 1992, avec une régression sensible des formations végétales naturelles (forêts et savanes arborées) et une progression marquée des formations anthropiques (mosaïques de cultures et de jachères) pour la même période. Il montre aussi que la recherche de corrélations NDVI/écoulement et résidus NDVI/résidus écoulement indépendamment de la pluie, souligne une relation significative dans les sous bassins de la Mékrou et de la Sota à Gbassè. Les résultats établissent ainsi une relation entre l'activité photosynthétique et l'écoulement, indépendamment de la pluie dans ces sous bassins. Cependant, dans les sous bassins de l'Alibori et de la Sota à Coubéri, on a pas pu mettre en évidence de lien significatif entre l'activité photosynthétique des types d'occupation du sol et l'écoulement. Toutefois, nos résultats sont limités par les données de NDVI qui ne reflètent que l'activité photosynthétique du couvert végétal. Par ailleurs, la longueur de la série des ces données est insuffisante pour tester efficacement l'influence de la dynamique des états de surface sur l'écoulement

<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.

Pour prévoir la production, les systèmes de surveillance de la sécurité alimentaire doivent être renseignés par des données sur les surfaces cultivées et sur le rendement. Ces données peuvent être estimées par les systèmes d'observations satellitaires à moyenne résolution spatiale, qui, par leur vision synoptique, constituent une source d'information particulièrement adéquate. En Afrique de l'Ouest, l'estimation des surfaces cultivées par télédétection reste cependant problématique en raison d'un domaine cultivé fragmenté, d'une grande hétérogénéité spatiale due aux conditions environnementales et aux pratiques culturales, et de la synchronisation des phénologies des agrosystèmes et des écosystèmes liée au régime des précipitations. Dans ce contexte, cette thèse présente, en trois volets, des développements méthodologiques originaux pour la caractérisation des systèmes agricoles d'Afrique de l'Ouest par télédétection. Les méthodes ont été développées à partir de séries temporelles MODIS (250 m à 500 m de résolutionspatiale) acquises sur le Mali. (i) La cartographie des surfaces cultivées a été réalisée à partir d'indices spectraux, spatiaux, texturaux et temporels dérivés des images. Deux approches ont été appliquées : une approche de type ISODATA consécutive à une segmentation du territoire basée sur les images MODIS et une approche de fouille de données basée sur des " motifs séquentiels ". Les produits cartographiques obtenus présentent une meilleure précision que les produits globaux " occupation du sol " existants (70% vs 50% en moyenne). Cependant, une part importante des erreurs d'omission et de commission (de 20% à 40%) reste incompressible en raison de la fragmentation du domaine cultivé. (ii) La cartographie des types de systèmes agricoles a nécessité un premier travail de typologie effectué à partir d'une BD d'enquêtes de terrain de l'Institut d' Economie Rurale de Bamako sur 100 villages. Trois types de systèmes agricoles ont été déterminés à l'échelle du village : céréales dominantes (mil, sorgho), cultures intensives dominantes (maïs, coton) et mélange de sorgho et de coton. La classification des systèmes agricoles à partir des indicateurs de télédétection précédemment cités a été produite par un algorithme de type Random Forest avec une précision globale de 60%. Les résultats mettent en évidence une combinaison optimale d'indicateurs comprenant le NDVI ainsi que la texture pour la caractérisation des systèmes agricoles. (iii) Enfin, pour le suivi des cultures, le produit phénologique MODIS a été testé et évalué à partir de variables phénologiques obtenues par simulations agro-météorologiques du modèle de plante SARRA-H. Les résultats montrent que ce produit comporte des incohérences dues au fort ennuagement de début de saison des pluies. Après suppression des données aberrantes, on montre que les dates de transition phénologique des surfaces cultivées issues de MODIS sont plus précoces de 20 jours comparées aux sorties du modèle de culture, en raison notamment de la nature mixte " agro-écosystème " des surfaces à l'échelle du pixel MODIS. Les résultats de cette thèse permettent de dégager de nouvelles pistes de couplage entre télédétection, données de terrain et modélisation agro-météorologique en apportant une information continue dans le temps et dans l'espace sur la caractérisation du domaine cultivé au " Sahel ".