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Medenine, Tunisia

Gamoun M.,Arid Regions Institute IRA
Journal of Arid Land | Year: 2014

Although the effects of non-grazing and heavy grazing on vegetation structure have been extensively studied in a wide range of ecosystems, the effects of moderate grazing on desert land are still largely unknown. Many management opportunities exist for increasing forage intake. In order to determine an optimal management method of desert rangelands with high heritage value, we examined the respective effects of heavy grazing, moderate grazing and non-grazing on total vegetation cover, species richness, the Shannon-Wiener diversity index and rangeland productivity. Sampling was done from 2010 to 2012 (from the second year after treatments were imposed) using permanent transects under different grazing intensities. While total vegetation cover, species richness, Shannon-Wiener diversity index, species composition and primary production were significantly greater on the ungrazed site and significantly weaker on the heavily grazed site, in contrast, moderate grazing had no significant effect on total vegetation cover, species richness, Shannon diversity index, species composition and primary production. These studies suggest that desert rangelands plant communities in general lack response to moderate grazing disturbance, and if managed properly they can provide a valuable source of feed for livestock. © 2014 Science Press, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.

Atia H.,Applied Thermodynamic Research Unit UR11ES80 | Snoussi A.,Applied Thermodynamic Research Unit UR11ES80 | Benbrahim A.,Applied Thermodynamic Research Unit UR11ES80 | Ilinca A.,University of Quebec at Rimouski | Boukchina R.,Arid Regions Institute IRA
IREC 2016 - 7th International Renewable Energy Congress | Year: 2016

A CFD analysis using ANSYS Fluent software was conducted to study the effects of collector slope on solar chimney's performances. Three solar chimney configurations, named A, B and C, which correspond to a slope of 0°, 2.5° and 5°, respectively, were studied. Both collector Radius and chimney height were fixed to 495m for the three configurations. For the three studied configurations, the pressure ratio was fixed to 0.9 and the solar radiation was varied from 200 W/m2 to 1100 W/m2. The results show that the thermodynamic performances of the solar chimney were enhanced by increasing the inclination angle of the collector roof. In fact, the power extracted from a sloped solar chimney power plant (SSCPP), the energetic and the exergetic efficiencies of the processes increase with increasing the inclination angle and the solar radiation value. © 2016 IEEE.

Aouadi D.,National Agricultural Research Institute of Tunisia INRAT | Aouadi D.,University of Carthage | Zorghi L.,Research Unit of Macromolecular Biochemistry and Genetics | Neffati M.,Arid Regions Institute IRA | Ben Salem H.,International Center for Agricultural Research in the Dry Areas
Journal of Animal and Feed Sciences | Year: 2015

The foliage of woody plants, Artemisia herba alba (ART), Eucalyptus globulus (EUC), Pistacia lentiscus (PIS), Rosmarinus officinalis (ROS) and Thymus capitatus (THY), growing in central Tunisia was analysed for contents of nutrients and phytocompounds, including essential oils (EOs) and tannins. PIS and THY were highest in neutral detergent fibre and condensed tannins, respectively. EUC had the highest levels of total phenols, total tannins and oxalates. The concentration of EOs was highest in ROS and THY (26.59 ml · kg-1 dry matter (DM) vs 14.14 ml · kg-1 of DM, respectively). The EOs profiles differed among all the plant species. ROS and EUC EOs were composed mainly of 1,8-cineole (27.86% and 50.19%, respectively) while ART's EOs were dominated by camphor (16.28%) and chrysanthenone (14.78%). Carvacrol (44.24%) was the chemotype of THY EOs. The major compound of PIS EOs was α-pinene (12.82%). Biological assay showed that tannins affect the nutritive value of these plants. With the exception of THY, the association of polyethylene glycol to substrates incubated in calibrated syringes resulted in a major increase of gas production (+21% to +136%). Differences in the profiles of EOs extracted from the five woody species suggest that these EOs could differ in their impact on digestion and performance of ruminants. © 2015, Polish Academy of Science. All rights reserved.

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