Bienvenu Sambou

Estimation of Herbaceous Fuel Moisture Content Using Vegetation Indices and Land Surface Temperature from MODIS Data

The monitoring of herbaceous fuel moisture content is a crucial activity in order to assess savanna fire risks. Faced with the difficulty of managing wide areas of vegetated surfaces, remote sensing appears an attractive alternative for terrestrial measurements because of its advantages related to temporal resolution and spatial coverage. Earth observation (EO)-based vegetation indices (VIs) and the ratio between Normalized Difference Vegetation Index (NDVI) and surface temperature (ST) were used for

Vegetation and fire readiness in main morphological units of Niokolo Koba National Park (Southeast Senegal)

Abstract Bush fires are the main cause of natural resource degradation in Niokolo Koba National Park. So-called “early fires” or management fires are considered an irreplaceable tool for land management in protected areas. A synthesis of the literature and field observation reveals that plateaus and slopes are the most prone to burning. Fire proneness depends mainly on vegetation characteristics. The main vegetation types on plateaus and slopes are shrub and arboreal savannah, respectively. These savannah types are both dominated by Combretaceae in the ligneous stratum, while in the herbaceous layer species of Poaceae family dominate. The predominance and state of Poaceae in the herbaceous layer are major indicators of fire readiness. It is sought to adopt a strategy for early fire implementation that minimizes impact on natural resources. Any strategy must include an operational system for monitoring herbaceous fuel conditions. Such a system could benefit from new remote sensing technologies when combined with field measurements in the most exposed zones.

EFFECTS OF DIFFERENT PRETREATMENTS ON THE GERMINATION OF Faidherbia albida (DEL.) A. CHEV. SEEDS

SUMMARY The difficulties of using sulphuric acid for removing the physical dormancy of Faidherbia albida seeds have resulted in a search for alternative methods of pretreatment of the seeds. This trial tested the efffciency of 10 alternative pretreatments. The results show that the sulphuric acid, manual scarification and scarification by hot wire, which achieved stable values of over 90% of germination of seeds after eight days, were clearly superior to the use of a seed gun (80% germination after 16 days at the optimal setting of the gun) or of hot/boiling water methods (less than 20% germination after 16 days). Due to the high capacity of seed gun (i.e. around 1 kg/minute), it appears that the gun method, although methods which treat seeds individually result in higher germination percentages, could be a useful way to treat large quantities of seeds. However, the optimal speed of the rotation of the gun must be determined beforehand for each lot of seeds.

Rainfall Variability in Sine Saloum River Basin in a Context of Climate Change and Variability

Drought is one of the most worrying manifestations of variability and change of climate in many West African countries. Due to its threats on human life, socio-economic activities, agricultural productivities, shortage of water, natural resources and environments, the problems related to drought have caught the attention of scientists, researchers and policy makers in recent decades. Original Research Article Doumouya et al.; AIR, 6(6): 1-12, 2016; Article no.AIR.25349 2 The aim of this paper is to characterize and analyze climatic events and their impact on water resources, environmental ecosystems and population. For this, we have selected rainfall time series of Sine Saloum river basin at Foundioune’s rain gauge. We have first conducted an exploratory analysis based on the graphic study. So, histograms relating to annual rainfall, monthly rainfall decadal, interannual monthly rainfall and interannual monthly averages, were analyzed separately compared to the corresponding average; this has highlighted the spatial and temporal distribution of intra and inter annual rainfall compared to the average and allowing viewing wet and dry years and months. We have secondly calculated the drought indices such as standardized precipitation index and normal precipitation index to evaluate climate fluctuations, characterize the progression of drought and its degree of intensity. This has also highlighted the deficit years and surplus years. In total, over the 43 years of the study period, we have counted 13 wet years and 20 dry years. We have also noted that 1971 was the wettest year and 2007 the least wet year. Characterization of these 30 deficit years has highlighted 3 categories of drought: mild drought, moderate drought and great drought. It appears from this study that the impacts of drought can be attributed in part to a deficit or erratic rainfall. Analysis of the results has showed the high vulnerability of the watershed to drought. Examination of drought years revealed a higher frequency in space and in the time of light drought. These results are very useful for drought monitoring, evaluation and mitigation.

Farmers’ contributions to the conservation of tree diversity in the Groundnut Basin, Senegal

Abstract Tree diversity in West Africa is threatened by intensified land uses and salinization, and farmers’ role in conservation of tree species is unclear. We hypothesized that farmers contribute to conservation of tree diversity through protection of trees in their agroforestry landscapes and compared the diversity and structure of the tree vegetation across landscape classes. Inventories were carried out in three villages in the Groundnut Basin in Senegal, assessing tree diversity, density and crown cover. Tree diversity as assessed by species accumulation curves was high in forests, but cultivated landscapes had comparable or almost comparable diversity, especially in the cases where the forest was planted or was affected by charcoal production. However, the occurrence of exotic species was higher in cultivated parts of the landscape, and although many species were in common, ordination plots indicated that forests and cultivated landscapes to some degree had different species composition. Salinity had a strong influence on vegetation, not only in the tans (salt marshes) but also across the other landscape classes. In conclusion, agroforestry landscapes in the three villages harbor considerable tree diversity, but insufficient to fully conserve the tree species. We argue that informing and including farmers in tree management in the region will contribute to overall conservation of tree genetic resources.

Régénération naturelle de Cordyla pinnata (Lepr. Ex. A. Rich.) Milne-Redh. dans une savane soumise au feu et au pâturage

Au Senegal, les formations forestieres sont sujettes a une degradation relativement importante, marquee par une diminution des superficies boisees, une reduction de la densite des especes et un changement de leur structure. Les possibilites de regeneration naturelle de plusieurs especes sont compromises. Cet etat de degradation n’a pas epargne les aires protegees comme celle de la foret classee de Fathala ou la plupart des especes ligneuses sont confrontees a un probleme de regeneration naturelle. Les facteurs mis en cause sont a la fois naturels et anthropiques. L’inventaire de la regeneration naturelle et la mise en place d’un dispositif de suivi en rapport avec le deficit hydrique, le feu et le betail, sur trois annees ont permis respectivement d’evaluer l’abondance de la regeneration naturelle de Cordyla pinnata (Lepr. Ex. A. Rich.) Milne-Redh. et d’etudier l’impact de ces facteurs sur la survie de cette regeneration. Les resultats montrent une forte densite de regeneration issue de semis naturels dominee par des germinations de l’annee en cours. Cependant, la survie de ces nombreuses germinations est compromise par ces differents facteurs. Le feu precoce, le feu tardif et le betail accentuent fortement la mortalite de la regeneration naturelle de l’espece. Les resultats revelent qu’en plus de la regeneration naturelle par voie de semis, Cordyla pinnata presente la capacite de rejeter ; ce qui contribue a favoriser la survie de l’espece.

Développements récents de l’Herbier de Dakar

The DAKAR Herbarium created in 1960 holds approximately 8000 plant specimens. Like many other African herbaria, activities have been greatly limited during the last decade due to lack of funding which again has lead to scientific isolation. As part of a collaboration with the University of Aarhus (Denmark) the herbarium is now being renovated and it will soon be fully operative. The main innovations during the last year included training of researchers, implementation of infrastructure and equipment, and addition of new specimens.