In Algerian desert, oases are characterized by the presence of date palm (Phoenix dactylifera L.) as a dominant species. This plant gives fruit but also creates a favourable microclimate for other crops. The date palm is essential for the oasis agro-ecosystem equilibrium, the latter being a group of small family farms, has been the subject of serious damages in recent years, it’s blossoming. Two cultivars are dominated redarding to their economic importance in local market with 96% (Ghars and Deglet Nour). Recently, a clear degradation of oases was noticed due to the lack of interest from growers to replace old and dead palms. These palm grove have aged palm, high height and a fragile stamina which limiting the cultural operations and affecting grimly the production. Actually, the old palm groves in the North-east of Algerian Sahara are divided into types: “Bour” and “Old palm groves”.

The scarcity of annual rainfall, which sometimes spreads over successive years, causes persistent droughts. In order to study the drought severity on the Algerian steppe, we analysed precipitation data (1985-2015) from the weather stations of Ain Sefra, El Bayadh, Tiaret and Djelfa, using drought meteorological indices: the mean deviation, the standardised precipitation index, the rainfall index and the frequency analysis of the rainfall series. Thus, we adopted the diachronic study by satellite remote sensing for the years 2002 (the driest year) and 2009 (the wettest year), which allowed us to better understand the evolution of the steppe rangelands surface and to better interpret their spatial-temporal changes. Drought, as determined by the mean deviation index, occurred during two periods (in sequence and corresponds to 55% the sequences of deficit years), one over 12 years (from 1994/1993 to 2006/2005) and the other over 5 years (1985-1990) and with isolated years. The results of the diachronic study of the vegetation change demonstrate the obvious divergence of the vegetation cover between 2002 and 2009. Drought has impacts on vegetation composition, growth, productivity, structure and functioning of ecosystems, which limits regeneration of vegetation cover.