L'ELEVAGE OVIN EXTENSIF EN TUNISIE : DISPONIBILITES ALIMENTAIRES ET INNOVATIONS POUR LA VALORISATION DES RESSOURCES FOURRAGERES LOCALES

N° ISBN - 978-2-7380-1284-5International audienceSheep farming plays a vital role in food safety in Tunisia. This paper aims to reflect the current status of sheep farming through an analysis of their food availability and limits. A study of the possibilities for improving the local feeding resources is then made identifying the innovations in this field. Results show that the decrease in pasture areas is caused by the over-grazing, the frequent droughts and the expansion of cereal crops and tree plantations. Use of concentrates becomes more frequent in livestock industry. These concentrates are heavily based on imported ingredients whose prices have tripled over the last two decades. Consequently, a renewed interest has been given to the use of local feed resources and looking for alternatives such as their partial or total replacement of the imported raw materials. The use of the local barley and field beans in the sheep feeding could ensure acceptable animal performances. In the arid and semi-arid Tunisian zones, thousands of hectares of fodder shrubs have been established, especially spineless cactus, Atriplex nummularia and Acacia cyanophylla. Other innovations in animal feeding demonstrated the effectiveness of alternative feed resources like using feed blocks which could represent a promising nutritional tool especially when animals are grazing on poor pastures, the use of multi-purpose shrubs, or several agricultural and agro-industrial by-products (treated straws, cakes, pulps...). A lack of adequate co-ordination and synergy between the different stakeholders is inhibiting the progress and implementation of transversal approaches that are necessary for the delivery of integrated sustainable policies

Obtaining evapotranspiration and surface energy fluxes with remotely sensed data to improve agricultural water management

The quantification of evapotranspiration from irrigated areas is important for agriculture water management, especially in arid and semiarid regions where water deficiency is becoming a major constraint in economic welfare and sustainable development. Conventional methods that use point measurements to estimate evapotranspiration are representative only of local areas and cannot be extended to large areas because of heterogeneity of landscape. Remote sensing based energy balance models are presently most suited for estimating evapotranspiration at both field and regional scales. In this study, SEBAL (Surface Energy Balance Algorithm for Land), a remote sensing based evapotranspiration model, has been applied with Landsat ETM+ sensor for theestimation of actual evapotranspiration in the Habra plain, a semiarid region in west Algeria with heterogeneous surface conditions. This model followed an energy balance approach, where evapotranspiration is estimated as the residual when the net radiation, sensible heat flux and soil heat flux are known. It involves in the input the remote sensing land surface parameters such as surface temperature, NDVI and albedo. Different moisture indicators derived from the evapotranspiration were then calculated: evaporative fraction, Priestley-Taylor parameter and surface resistance to evaporation. These calculated indicators facilitate the quantitative diagnosis of moisture stress status in pixel basis. Thestudy area contains extremes in surface albedo, vegetation cover and surface temperature. The land uses in this study area consists of irrigated agriculture, rain-fed agriculture and livestock grazing. The obtained results concern the validation of the used model for spatial distribution analysis ofevapotranspiration and moisture indicators. The evaluation of dailyevapotranspiration and moisture indicators are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that SEBAL can be considered as an operational method to predict actual evapotranspiration from irrigated areas having limited amount of ground information

QUALITE DES MODELES NUMERIQUES DE TERRAIN DERVIES PAR CORRELATION AUTOMATIQUE

Digital Terrain Models are plying an important role as information layer, mainly with the development of geographic information systems, since they describe the topographic surface of the terrain and hence it constitutes a valuable support for the study of variety of geographical and environmental events. With the advent of digital techniques and the advantages they are offering in terms of automation and precision, users are adopting image matching techniques to derive automatically Digital Terrain Models. The quality of these DTM are determined by different factors (photo scale, scanning resolution and software parameterization). This paper is a contribution to evaluate the influence of some of some factors on the final accuracy of DTM derived by correlation. In this respect, different tests were carried out on two photo scales (1/7500 an 1/20000) flown on varying topography. The photos were scanned to 20, 25, 32 and 42 microns pixel sizes and digital terrain models were derived using ViruoZo software from Supresoft. The assessment of the derived DTMs quality was based on qualitative (visual comparisons of contours) and quantitative ( RMS computed from residuals on ground check points) criteria. Results showed that, in rugged terrain, DTM derived from 1/20000 photos are accurate to 32cm, which may enable deriving contours with 1 m interval. The introduction of break lines prior to the correlation seems to have less influence on the accuracy of derived DTM when the generated grid is very dense, but contributes to reduce the editing burden. The high accuracy of automatically derived DTM may contribute to make less tight the map to photo scale ratio. For instance mapping at 1/5000 from 1/20000 photos can preserve the height accuracy, while with conventional methods, height accuracy at 1/5000 map scale is preserved usually for mapping from 1/12000. 1

Geochemical characterization the waters of Foggaras the Continental Intercalary Aquifer of Timinoune region (south west Algeria)

The study of the Continental Intercalary (C.I) groundwater of the region of Timimoune (southwestern Algeria), based on physico-chemical data (major elements), allowed to understand the geochemistry of foggaras water. The aquifer is contained in the formations of the Lower Cretaceous (Albian and Barremian). The waters are strongly mineralized with an average value 2g / l.The waters have a clear predominance of facies chlorinated-sodium. The risk is high to excessive soil salinization, and the risk of medium alkalinity to very high. Statistical analysis led us to reach two conclusions, the first is that, variable electrical conductivity (EC), dry residue (RS), Na+, Ca2+, Cl-, SO4 --, mineralization, are best correlated and responsible the signing of the mineral load of water, the second is that the nitrate ion (NO3-) opposite to the above-mentioned variables mark its anthropogenic origin. Keywords: Continental Intercalary, mineralization, salinity, PCA, Nitrat

Sterol composition of caper (Capparis spinosa) seeds

Caper is a perennial shrub of the Mediterranean Basin. The most important economical species is Capparis spinosa. Sterols of C. spinosa seed oil isolated from seven Tunisian stands were identified andquantified. C. spinosa contained  high levels of phytosterols (2240.4 mg/kg of total extracted lipids), of which -sitosterol, with 1390 mg/kg, was the most abundant (57.53%). Campesterol and stigmasterol accounted for 382 and 265 mg/kg, respectively (17.05 and 11.85% of the total sterols, respectively). C. spinosa seed oil also contained a high level of 5-avenasterol (6%). We detect also brassicasterol (3.39 mg/kg). Cholesterol and campestanol are detected in much lower levels. These results bring attention to the richness of C.spinosa seed oil with sterols which are the most important class of the minor components

Speech Enhancement via EMD

WOSInternational audienceIn this study, two new approaches for speech signal noise reduction based on the empirical mode decomposition (EMD) recently introduced by Huang et al. (1998) are proposed. Based on the EMD, both reduction schemes are fully data-driven approaches. Noisy signal is decomposed adaptively into oscillatory components called intrinsic mode functions (IMFs), using a temporal decomposition called sifting process. Two strategies for noise reduction are proposed: filtering and thresholding. The basic principle of these two methods is the signal reconstruction with IMFs previously filtered, using the minimum mean-squared error (MMSE) filter introduced by I. Y. Soon et al. (1998), or thresholded using a shrinkage function. The performance of these methods is analyzed and compared with those of the MMSE filter and wavelet shrinkage. The study is limited to signals corrupted by additive white Gaussian noise. The obtained results show that the proposed denoising schemes perform better than the MMSE filter and wavelet approach

Chemical polymorphism of essential oils from populations of Laurus nobilis grown on Tunisia, Algeria and France.

The compositions of the essential oils isolated from the aerial parts of tree Mediterranean populations of Laurus nobilis L. collected during the flowering phase on Tunisia, Algeria and France, were studied by GC and GC-MS. The analysis has allowed identifying 54 components. The main components were 1,8-cineole, α-terpinyl acetate (10-18.6%), methyl eugenol (10-22.1%), sabinene (1.2-8%), eugenol (1.2-11.7%) α-pinene (tr-4.5%) and β-pinene (0.4-4.2%). The monoterpene fraction was dominant in all the oils analysed and consisted mainly of oxygenated monoterpenes. The oils from the tree populations studied showed a clear chemical polymorphism. The principal component and the hierarchical cluster analyses separated the Laurus nobilis leaf essential oils into three groups

Etude en rupture d'un composite à fibres végétales d'Alfa

National audienceThe behavior under monotonic loading of reinforced natural fibre composites begins to be fairly well known today. However, the fracture behavior is still poorly controlled. This work describes a numerical approach developed to simulate the propagation mechanism of a matrix crack in natural fibre reinforced composites.To this end, the fracture behavior of a REV; constituted of alfa fibre, with linear anisotropic behavior, surrounded by a matrix with non-linear viscoelastic behavior, was investigated using a finite element model. The analysis of the fracture behavior of the composite alfa fibre / epoxy resin shows that under uniaxial longitudinal or transverse load to the fibre, a crack initiated in the matrix is propagated perpendicularly to the direction of the load. Near the interface, the energy release rate decreases and this energy is higher in the presence of interfacial debonding areas generated by problems of fibre wettability. Reaching the interface, the crack is either blocked or deflected. Once deflected, the crack propagates along the interface and causes the complete debonding of the fibre.Le comportement sous chargement monotone des composites renforcés par des fibres naturelles commence à être assez bien connu aujourd'hui. Cependant, le comportement à la rupture est encore mal maîtrisé. Le présent travail décrit une approche numérique développée pour simuler le mécanisme de propagation d'une fissure matricielle à l'interface fibre végétale alfa / résine époxy dans les composites à matrice polymère. A cette fin, le comportement à la rupture d'un VER constitué d'une fibre unitaire d'alfa, de comportement linéaire anisotrope, entourée d'une matrice de comportement non linéaire viscoélastique, a été étudié à l'aide d'un modèle éléments finis. L'analyse du comportement à la rupture du composite fibre alfa/résine époxy montre que sous l'action d'un chargement uniaxial, longitudinal ou transversal par rapport à la fibre, une fissure initiée dans la matrice se propage perpendiculairement au sens de la sollicitation. Au voisinage de l'interface, le taux de restitution d'énergie diminue et ce taux est plus élevé en présence de zones de non adhésion générées par des problèmes de mouillages. Arrivée à l'interface, la fissure est soit bloquée soit déviée. Une fois déviée, la fissure se propage le long de l'interface et entraîne la décohésion de la fibre