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31.
Understanding pastoral mobility: the case of Senegalese Fulani 总被引：2，自引：0，他引：2
HANNE KIRSTINE ADRIANSEN 《The Geographical journal》2008,174(3):207-222
Based on a case study from Sahelian Senegal, this paper analyses how various actors perceive the importance of pastoral mobility and presents issues of importance for understanding the use of mobility among Fulani of Ferlo. One knowledge system is a scientific one, the 'new rangeland paradigm'. According to this, pastoral mobility is a means to balance variability in dryland resources; hence, 'nature' is the point of departure. Another knowledge system is local pastoral knowledge. For the pastoralists, the well-being of their animals is the point of departure and mobility is used to ensure that the livestock are in good condition. The paper shows that it is important to distinguish between mobility of pastoralists and of their herd; even though the pastoralists of northern Senegal have become semi-sedentary, their herds are still quite mobile. The pastoralists are willing to move around within a small territory, which they consider their place, but are unwilling to employ large-scale mobility themselves. Mobility is not of importance for their ethnic identity and some use paid herders to care for their livestock. By looking at both knowledge systems, we achieve a better understanding of pastoral mobility and how this may change in the future. 相似文献
32.
Maylis Labonne Eric Morize Pierre Scolan Raymond Lae Eric Dabas Marcel Bohn 《Estuarine, Coastal and Shelf Science》2009,82(4):673-681
The adaptive mechanisms on the early life stages of fishes to hypersaline stress are still poorly understood and probably determine the resistance of a population to disruption, compared with other less plastic species. The Casamance River in Senegal is an ideal location to test the adaptation to salinity as a dam was built in 1998 to exclude saline water intrusion. This lowered the salinity from 70 to 5 upstream and 60 downstream. The salinity influence on the growth in the early life of three West African fish species (Ethmalosa fimbriata, Sarotherodon melanotheron, and Tilapia guineensis) was studied using the width of microstructures in the otoliths and the individual migratory behaviour analysed from strontium (Sr) to calcium (Ca) ratios in the otoliths. The Sr:Ca ratio was quantified along individual transects measured from the posterior edge of the otolith to the core. The fishes were sampled on both sides of the dam that separated water with low salinity upstream from metahaline and hyperhaline water downstream.The results showed that salinity has different influence on the growth of each species. Ethmalosa fimbriata has the highest growth during the first 180 days in the freshwaters, indicating growth inhibition in the hyperhaline areas. For the two other species no growth difference were found. The Sr/Ca ratio varied widely, in Tilapia and Sarotherodon from below the dam. Individual life histories were more heterogeneous than upstream and showed a crossing of the dam for some individuals which could reach half of the fishes analysed. On the contrary in E. fimbriata, despite the large range of salinity, identical Sr/Ca profiles were found both upstream and downstream. This indicated that Sr/Ca ratio was not appropriate to evaluate life history patterns linked to salinity for this specie. 相似文献
33.
Michel Ritz Jean-Claude Parisot S. Diouf A. Beauvais F. Dione M. Niang 《Journal of Applied Geophysics》1999,41(4):105
The electrical properties of several tens of metres of lateritic weathering mantle were investigated by using electrical resistivity tomography (ERT) in two basement areas of eastern Senegal. The field survey was conducted along two profiles providing continuous coverage. Colour-modulated pseudosections of apparent resistivity vs. pseudo-depth were plotted for all survey lines, giving an approximate image of the subsurface structure. In the area underlain by granitic basement, the pseudosection suggests a very inhomogeneous weathered layer in which the apparent resistivity changes more rapidly than thickness. In the second area, underlain by schists, the lateral changes in electrical properties are less pronounced than those of the granitic area. Interpretation of 2D Wenner resistivity data yielded considerable detail about the regolith, even without pit information. In both areas, the near-surface topsoil comprising undersaturated lateritic material is highly resistive. The intermediate layer with low resistivities (e.g., 20–100 Ωm) contains clays including small quantities of water. The third, highly resistive layer reflects the granitic basement. Comparison of ERT survey results with pit information shows general agreement and suggests that ERT can be used as a fast and efficient exploration tool to map the thick lateritic weathering mantle in tropical basement areas with hard rock geology. 相似文献
34.
The article evaluates the impact of EU fishing activities for the sustainable development of Senegal's maritime fishery. An evaluation of Senegalese fisheries’ policy discourse introduces the idea that Senegalese fisheries’ policies have not been fully compatible with the sustainable development of the country's fishery sector. A comparative analysis of the sustainable development impacts associated with the activities of different fishery user groups shows that managed activities of heterogeneous user groups can benefit the sustainable development of the sector. Conclusions suggest that the heterogeneity of the user groups frequenting Senegal's marine fishery system can be capitalised upon through allocating fishery access in accord with each group's ability to generate sustainable development benefits. On the basis of these findings the article suggests that the presence of an EU fleet in Senegalese waters could play a meaningful role in ensuring the sustainable development of Senegal's marine fishery. 相似文献
35.
Gorm Dybkjær Thomas Theis Nielsen Kjeld Rasmussen Michael Schultz Rasmussen Lars Boye Hansen Assize Touré 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):125-135
A NOAA AVHRR data set covering Senegal and parts of the surrounding countries during the period from 1987 to present is under construction and improvement in an ongoing collaboration between Centre de Suivi Écologique (CSE). Dakar. Senegal, and Institute of Geography, University of Copenhagen (IGUC). This paper details the entire processing chain from raw images to a properly calibrated, geometrically rectified and cloud-masked time-series tracking a number of well-defined variables. Two vital aspects of this time series, the cloud masking procedure and the geometrical rectification, are evaluated in detail. A two-step, multi-criteria cloud masking procedure requiring a manual input does not consistently improve the quality of the data set compared to the simpler, automated procedure. With respect to geometrical rectification an accuracy on the order of I km is obtained. Finally, suggestions for further improving the data set are forwarded 相似文献
36.
As part of the restoration of degraded land south of the Sahara, an experimental study has been carried out on the germinative properties of the seeds of seven Sahelian leguminous species (Cassia obtusifolia, Cassia occidentalis, Indigofera astragalina, Indigofera senegalensis, Indigofera tinctoria, Sesbania pachycarpa and Tephrosia purpurea). Analysis of the effects of temperature, pretreatment and water potential has enabled definition of their optimum germination conditions. For the temperature range studied (20–40°C), germination capacity was significantly greater between 30 and 35°C for all species. All species except Cassia obtusifolia developed a very strong integumental inhibition which was easily eliminated by mechanical scarification or immersion in concentrated sulphuric acid (H2SO4, 95%). Study of the influence of water potential on germination showed that these species are able to germinate at relatively low water potentials. Different patterns of response to water stress are highlighted and explained by the different behaviours of these species in the semi-arid conditions of the Sahelian environment. 相似文献
37.
《Limnologica》2016
The Senegal River is of intermediate size accommodating at present about 3.5 million inhabitants in its catchment. Its upstream tributaries flow through different climatic zones from the wet tropics in the source area in Guinea to the dry Sahel region at the border between Senegal and Mauritania. Total suspended matter, particulate and dissolved organic carbon and nitrogen as well as nutrient concentrations were determined during the dry and wet seasons at 19 locations from the up- to downstream river basin. The aims of the study were to evaluate the degree of human interference, to determine the dissolved and particulate river discharges into the coastal sea and to supply data to validate model results. Statistical analyses showed that samples from the wet and dry season are significantly different in composition and that the upstream tributaries differ mainly in their silicate and suspended matter contents. Nutrient concentrations are relatively low in the river basin, indicating low human impact. Increasing nitrate concentrations, however, show the growing agriculture in the irrigated downstream areas. Particulate organic matter is dominated by C4 plants during the wet season and by aquatic plankton during the dry season. The total suspended matter (TSM) discharge at the main gauging station Bakel was about 1.93 Tg yr−1 which is in the range of the only available literature data from the 1980s. The calculated annual discharges of particulate organic carbon (POC), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are 55.8 Gg yr−1, 54.1 Gg yr−1, and 5.3 Gg yr−1, respectively. These first estimates from the Senegal River need to be verified by further studies. 相似文献