| Autor: |
Hirche, Aziz, Salamani, Mostefa, Abdelmadjid, Boughani, Nedjraoui, Dalila, Hourizi, Ratiba, Oukil, Youcef, Slimani, Halima, Khedache, Zina, Belala, Fahima, Hamouda, Tahar Ait, Adi, Nacer, Grandi, Mohamed |
| Předmět: |
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| Zdroj: |
Environmental Research Journal; 2015, Vol. 9 Issue 3, p351-368, 18p |
| Abstrakt: |
In 1978, several observatories, aiming ecological monitoring,were settled in the arid high plains of South west Algeria. These observatories are now integrated in an international network called ROSELT (Long Term Ecological Monitoring Observatories Network) administered by the OSS (Observatory of the Sahara and the Sahel). A study area included in one of these observatories was monitored on more than thirty years. It is part of Algerian steppe, the most widespread of the Maghreb. The results showed that this area has undergone profound changes. These modifications concerned both physical and biological components. The parameters considered include vegetation, flora, and soil surface properties. It appears that land cover has changed and former vegetation dominated by Stipa tenacissima, Lygeum spartum and Artemisia herba alba has disappeared. New species, like Atractyis serratuloides, Salsola vermiculata and Noaea mucronata, rare in 1978 are now dominant, in relation with a dynamic of degradation. The largest decline is observed for Stipa tenacissima vegetation units constituting 2/3 of the landscape in 1978 and occupying just 1/10 in 2010. The vegetation cover has also significantly declined. In 1978, the average coverage was over 34%, whereas now it is less than 19% of the total. The biodiversity has also changed. The floristic richness has decreased. In 1978, 234 species were inventoried in the study area, for 134 in 2005 and only 94 in 2011. On the other side, the family composition and phytogeographical spectra have also changed, in the sense of an adaptation to xeric conditions. This can be explained by severe spells of drought combined by an exponential rise of livestock during the last 30 years. Finally, even if the last years were wetter and a slight improvement in vegetation cover was observed, there is no evidence for a desertification in reverse, as it is considered for the Sahel. On the contrary, we are still in a degradation process on the long term. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
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