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Accueil du site → Doctorat → Belgique → La dégradation des systèmes écologiques sahéliens : effets de la sécheresse et des facteurs anthropiques sur l’évolution de la végétation ligneuse du Ferlo (Sénégal)

Université Catholique de Louvain (1995)

La dégradation des systèmes écologiques sahéliens : effets de la sécheresse et des facteurs anthropiques sur l’évolution de la végétation ligneuse du Ferlo (Sénégal)

Vincke Caroline.

Titre : La dégradation des systèmes écologiques sahéliens : effets de la sécheresse et des facteurs anthropiques sur l’évolution de la végétation ligneuse du Ferlo (Sénégal)

Auteur : Vincke Caroline.

Université de soutenance : Université Catholique de Louvain

Grade : Doct.-ing. : Agron. : Eaux et Forêts (1995)

Résumé
The combined effects of climate change and human pressure have led to the progressive degradation of natural resources in semi-arid regions. Woody taxa in these regions play an important role in the functioning and services provided by semi-arid savannah by serving as forage for both domestic and non-domestic grazers. Maintaining the functioning of semi-arid savannas thus requires understanding the dynamics of these communities of woody taxa and their responses to exogenous forces, such as climate. To better understand the dynamics of woody taxa in semi-arid environments we collected dendrometric characteristics from five field sites along an environmental gradient in the Ferlo region of central Senegal. Density and basal area were found to be greater in the northern part of the zone, contrasted with the distance between individuals and crown cover, which is greater in the southern part of the zone. Stand structure estimated from the distribution according to height and diameter at breast height shows a preponderance of individuals in the shrub layer, although with a significant representation of the tree layer in southern Ferlo. Stand regeneration was better in the south and less effective in the north. There was a trend towards the rejuvenation of populations belonging to the dominant species. There were only three species for which degradation was not apparent (Balanites aegyptiaca, Acacia raddiana and Dalbergia melanoxylon), all of which have important ethnobotanical uses, suggesting that human use of taxa can play an important role in preventing degradation. Three distinct groups of woody taxa were found to correspond to gradients of precipitation, topography, and human land use pressure. Our results suggest an important role in the management and reintroduction of woody species in the Sahel and the regulation of pastoral techniques necessary for the rehabilitation of the agro-pastoral zone of Senegal.

Mots Clés : COUVERT VEGETAL ; ECOSYSTEME ; DEGRADATION ; SECHERESSE ; DESERTIFICATION ; RESSOURCES NATURELLES ; FACTEUR ANTHROPIQUE ; LIGNEUX ; SENEGAL FLEUVE ; ZONE SOUDANOSAHELIENNE ; FERLO

Présentation (IRD )

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