Abstract: Abstract: The green dam is one of Algeria's greatest environmental achievements. However, few studies have focused on this area and particularly on its dynamics. This is what we will be examined in this work through a typical region where this reforestation was initiated, the forest of Moudjbara, located in Djelfa. The visual classification of Landsat satellite images 1972, 1987; 2003 and 2016 coupled with field surveys was selected. To limit the exogenous variations, the sun-synchronous satellite images were chosen at the same season, the autumn. Phytoecological surveys based on mixed sampling were performed. In terms of area, afforestation after planting reached about 6 500 ha in 1987 and 7985 ha in 2003 while in 2016 it reached 8500 ha, occupying nearly one third of the total area of the area study. Nevertheless, crops, especially in areas where reforestation has declined, are increasing. Phytosanitary status is a concern but natural forests seem less affected with 1.2 nests per tree in natural forest and 1.85 in reforestation. The comparison between original and reforested forest formations shows that biodiversity is greater in natural forests and the difference between reforestation and natural forest decrease with time, the similarity index between the natural forest and reforestation for the year 2002 is estimated at 63% and it reaches 76% in 2018 for perennial species. The most notable changes are in the nearby steppe area, which is undergoing advanced degradation. The crops which occupied only 1.29% of the study area currently cover 12% of the territory. These work shows that reforestation has relatively maintained their original areas, although growing crops. Contrariwise, the phytosanitary quality and the biodiversity of the stand are less satisfactory compared to natural stands. The rangelands are undergone deep changes which weaken their long-term future and question the survival of livestock farming in these zones.