Structure and spatiotemporal dynamics of plant cover in Sahelian rangeland of Niger

Abstract. The extreme north of the south-central region of the Republic of Niger is characterized by a semi-arid climate. Pastoralism constitutes the primary livelihood in this area. This study integrates dendrometric and phytosociological surveys with remote sensing to evaluate changes in floristic composition and structure. Vegetation inventory was conducted on 2,500 m2 plots using the Daget and Poissonet method, identifying 16 plant species, including six woody and ten herbaceous species, belonging to five botanical families. The woody species were dominated by Rhamnaceae (6%) and Zygophyllaceae (6%), while Poaceae (44%) and Fabaceae (38%) were the most represented herbaceous families. Diameter class distribution indicated that individuals measuring 20–35 cm comprised nearly 50% of the woody population, with a shape parameter C = 2.17, reflecting a monospecific population dominated by young or small-diameter individuals. Canopy height analysis revealed that trees within the 4–6 m (47.69%) and 2–4 m (24.61%) ranges were predominant. Analysis of biological and phytogeographic types revealed the dominance of therophytes (56.03%) and hydrophytes (0.47%), while woody species were predominantly pantropical (33.35%) and paleotropical. NDVI MODIS 250 m indicated significant variability in vegetation cover. Specific species contributions to total coverage were quantified as follows: Alysicarpus ovaliofolius (54.86%; 164.59 m2), Zornia glochidiata (18.04%; 54.14 m2), Echinochloa colona (15.11%; 15.11 m2), Cenchrus biflorus (4.05%; 12.10 m2), and Schoenfeldia gracilis (3.50%; 10.50 m2). These findings highlight the importance of integrating remote sensing dataset and field dataset to enhance understanding of pastoral resource for the sustainable management of grazing ecosystems in semi-arid environments.