Study of the Impact of Dune Fixation on Land Use in the Semi-arid Stage: Djelfa, Algeria

The various dune fixation works carried out at the level of the dune belt are extremely useful, on the one hand to fight against desertification via the creation of a microclimate which ensures the ecological sustainability of fragile ecosystems, and on the other hand, to improving the way of life of rural populations. In this context, carry out a diachronic study, with the aim of quantifying the floristic diversity after 31 years of planting. Also, the application of Factorial Correspondence Analysis (FCA) and CAH to 118 statements and 74 species revealed 4 plant groups. The main factors that determine them are: slope (Axis 1), soil humidity (Axis 2). The analysis of the results of the diachronic study shows that the overall percentage of vegetation increases in line with the altitudinal gradient, it occupies the lowest topographies of the dune where soil humidity is high and the action of the wind is minimal; windward topographies are generally difficult to colonize; they are drier and more exposed to the prevailing wind (SW), on the other hand the leeward topographies which are in shelter are cooler and therefore easily colonizable. Each fixing species occupies the dune differently as well: Retama retam Webb., grows across the entire dune at different topographies and exposures. Tamarix gallica L. colonizes all the topographies of the dune except the summits at high altitudes exposed to the wind. Tamarix aphylla (L.) Karst and Eleagnus angustifolia L. colonize the lower slopes and inter-dune spaces. Lycium arabica Boiss., recorded a success rate of less than 10%, especially in topographic position facing the wind.