Download or read book La dynamique d un syst me fluvial et des zones humides associ es en Afrique soudano sah lienne au cours de l Holoc ne written by Aline Garnier and published by . This book was released on 2013 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le système fluvial est façonné par des flux hydrologiques et de matières dont la dynamique dépend essentiellement des conditions environnementales au sein du bassin versant. Les enregistrements sédimentaires du fond de vallée représentent alors un indicateur clé de l’évolution des relations Nature/Société. Pourtant, en Afrique de l’Ouest, la recherche s’est souvent concentrée sur d’autres milieux, en particulier lacustres. Dans ce contexte, nous proposons un modèle d’évolution sur le temps long d'un système fluvial afin de s’interroger sur les variables de contrôle (naturelles et/ou anthropiques) ayant pu intervenir. Cette recherche s’appuie sur l’étude du bassin versant du Yamé, un affluent de rive droite du Niger (Pays Dogon, Mali). Deux approches ont été développées : (1) une approche géomorphologique qui permet de reconstituer les dynamiques hydro-sédimentaires de la vallée du Yamé et (2) une approche biogéographique qui, au travers de l’analyse des phytolithes contenus dans les dépôts, nous renseigne sur l’évolution de la végétation au cours de l’Holocène. Ce travail de thèse permet de mieux comprendre les transformations du système fluvial en réponse aux crises climatiques. Enfin, il questionne aussi les conséquences environnementales des transitions économiques, sociétales et techniques des derniers millénaires, telles que l’émergence de l'agriculture, de l’élevage, de la métallurgie et plus récemment l’accroissement de la population. Nous proposons ainsi d’apporter de nouvelles connaissances sur l’évolution climatique et anthropique de l’Afrique de l’Ouest et plus généralement sur l’impact de l’anthropisation sur les systèmes fluviaux soudano-sahéliens.

Download or read book Les zones humides africaines cologie techniques d tude et gestion written by George Edward Hollis and published by . This book was released on 1986* with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Complementarity of Feed Resources for Animal Production in Africa written by John E. S. Stares and published by ILRI (aka ILCA and ILRAD). This book was released on 1992-01-01 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stylosanthes as a Forage and Fallow Crop written by P. N. de Leeuw and published by ILRI (aka ILCA and ILRAD). This book was released on 1994-01-01 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: The biology of Stylosanthes and its importance in West Africa and Latin America; The screening and evaluation of Stylosanthes germplasm; The dynamics, nutrient requirements, pests and diseases of Stylosanthes species; Stylosanthes-based pastures for livestock production; The integration of Stylosanthes into cropping systems; Seed production of Stylosanthes.

Download or read book Remote Sensing and Water Resources written by A. Cazenave and published by Springer. This book was released on 2016-05-04 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a collection of overview articles showing how space-based observations, combined with hydrological modeling, have considerably improved our knowledge of the continental water cycle and its sensitivity to climate change. Two main issues are highlighted: (1) the use in combination of space observations for monitoring water storage changes in river basins worldwide, and (2) the use of space data in hydrological modeling either through data assimilation or as external constraints. The water resources aspect is also addressed, as well as the impacts of direct anthropogenic forcing on land hydrology (e.g. ground water depletion, dam building on rivers, crop irrigation, changes in land use and agricultural practices, etc.). Remote sensing observations offer important new information on this important topic as well, which is highly useful for achieving water management objectives.Over the past 15 years, remote sensing techniques have increasingly demonstrated their capability to monitor components of the water balance of large river basins on time scales ranging from months to decades: satellite altimetry routinely monitors water level changes in large rivers, lakes and floodplains. When combined with satellite imagery, this technique can also measure surface water volume variations. Passive and active microwave sensors offer important information on soil moisture (e.g. the SMOS mission) as well as wetlands and snowpack. The GRACE space gravity mission offers, for the first time, the possibility of directly measuring spatio-temporal variations in the total vertically integrated terrestrial water storage. When combined with other space observations (e.g. from satellite altimetry and SMOS) or model estimates of surface waters and soil moisture, space gravity data can effectively measure groundwater storage variations. New satellite missions, planned for the coming years, will complement the constellation of satellites monitoring waters on land. This is particularly the case for the SWOT mission, which is expected to revolutionize land surface hydrology. Previously published in Surveys in Geophysics, Volume 37, No. 2, 2016