The Manga located, in the South-East of Niger knows wind erosion. This form of degradation favored the creation of sharp dunes. To remedy this situation, programs to fight against sand dunes are implemented. This study is conducted in Guidan Kadji (Maïné-Soroa). It compares the herbaceous flora of a treated dune that has received manure, a natural course and a living dune in the vicinity of Guidan Kadji. The method of aligned quadrat points was used for the phytosociological study. The treated dune has 24 species, 10 species for the natural course and 3 species for the living dune, the best represented families are the Poaceae with 9 species. Therophytes occupy more than 80% of the gross and weighted spectra. The species. Guineo-Congolese-Sudanese-Zambézian is the dominant phytogeographic type with more than 70% in the gross and weighted spectra. The cover is 4.25%, 71.02% and 95.81% for live dune, treated dune and rangeland respectively. The qualified forage is 1339.65 kg DM/ha or 1.33 T DM/ha for the natural dune versus 703.44 kg DM/ha or 0.70 T DM/ha for the treated dune. It is practically null (2.04 kg DM/ha or 0.002 T DM/ha) on the live dune. Overall, the regularity (>0.60 bits) is high and the Sörensen similarity (>80%) between the treated dune and the natural course is high. This study demonstrated that dune fixation can restore the flora of degraded dune systems, especially if the site is close to residential areas.

In Niger in general and particularly in the department of Ouallam located in the Northern part of the area of Tillabéri, the natural resources undergo since decades a thinning down without precedent under the influence of several factors. The aim had by this work is to characterize the factors responsible for this environmental pollution on a local scale. To this end, an investigation of perception coupled to observations into the ground was carried out into the aspects relating to the causes of the degradation of the grounds. The analysis of the causes of landscape degradation was categorized in climatic, physical and anthropic factors. The results raise that with a standardized index of pluviometry (ISP) varying from -2,54 to 2,24, precipitations constitute the principal climatic factor influencing environmental dynamics. In the physical plan, the units of the relief evolve in basins slopes where the degradation of the plates is reflected on the other components. The factors anthropic causing the dynamics of the local ecosystems are: extension and the overexploitation of the grounds, cut of wood, the clearing, overgrazing, exploitation of the fodder and the residues of the cultures. The surveyed people affirmed the regression of the vegetation and the progression of the naked grounds, respectively to 94,91 % and 38,43 % of the guarantors. According to the population, the progressive degradation of the environment is caused mainly by the anthropic exploitation and bad pluviometry, respectively 93,38 % and 66,91 % of the appreciations made by the guarantors.