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Tunis, Tunisia

Zitouna-Chebbi R.,INRGREF | Prevot L.,French National Institute for Agricultural Research | Jacob F.,IRD Montpellier | Mougou R.,INRGREF | Voltz M.,French National Institute for Agricultural Research
Agricultural and Forest Meteorology

The current study addressed the consistency of eddy covariance (EC) measurements collected in sloping conditions within a hilly agricultural catchment. In the context of operational monitoring and modelling devoted to decision support, it is important to increase the knowledge of surface fluxes under conditions of hilly topography. The two-metre-high EC measurements were collected at the field scale within the two opposite rims of a V-shaped catchment located in northeastern Tunisia on the southern shore of the Mediterranean Basin. Measurements were collected under bare soil conditions to enhance the effects of the slopes. The data pre-processing and quality control measures were conducted using standard procedures. In assessing the consistency of the EC measurements we first compared the airflow inclinations captured by the EC measurements against the topographical slopes captured by a Digital Elevation Model; we then assessed the energy balance closure. The analysis of the micrometeorological data indicated specific regimes: externally driven winds; forced convection; and stability conditions close to neutrality or low instability. The two dominant wind directions induced upward and downward flows on the two opposite rims. For the upward flows, the airflow inclinations followed the topographical slopes on both fields. For the downward flows, the flows followed the topographical slopes on the southern rim and were almost horizontal on the other rim. In all cases, and especially for the upward flows, the energy balance closure was similar to that reported in the literature. Overall, the behaviour observed for upward flows was close to that reported in the literature for flat conditions, whereas the downward flows exhibited different trends. The different trends we observed for the downward flows were ascribed to the bubble separation zone that implies streamline dilatation, turbulence and reverse flows. Future investigations should address the vegetation conditions. The expected outcomes are of importance for revisiting the operational methods devoted to the estimation of evapotranspiration. © 2012 Elsevier B.V. Source

Amri I.,FSB | Hamrouni L.,INRGREF | Hanana M.,CBBC | Gargouri S.,INRAT | And 2 more authors.
Biological Agriculture and Horticulture

The chemical composition, physico-chemical properties, and antifungal and herbicidal activities of essential oils obtained by hydrodistillation from needles, stems and cones of Pinus halepensis Miller were investigated. The chemical composition analysed by GC and GC/MS varied significantly among organs. Among the 67 identified components, α-pinene (63% and 51.7%, respectively, in stems and cones) and (Z)-caryophyllene (33.9% in needles) were found to be the major ones. Moreover, it was found that chemical composition of essential oils extracted from different organs of P. halepensis Miller growing in Tunisia showed noteworthy differences with the same species cultivated in Algeria, Morocco, Greece and Italy based on a comparison with published results. In addition, the physico-chemical properties of essential oils from different organs of P. halepensis were analysed. The analysis of the refraction index, density and acid index of different oil samples showed a weak variability among organs. The in vitro antifungal activity of the essential oil samples evaluated against 10 cultivated crop fungi was found to be low, probably due to the low level of oxygenated compounds in P. halepensis oils. In contrast, the herbicidal activity investigated towards three common weeds in Tunisian cereal crops was very strong and seed germination was inhibited at 2 μl ml-1. Thus, P. halepensis essential oil appears to have more value as a bioherbicide than as a biofungicide. © 2013 Taylor & Francis. Source

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