Fallowing is widely used to restore soil biological fertility, yet its effectiveness may vary across pedoclimatic regions. In arid environments such as the Sahel, recovery may be constrained by low and variable rainfall, a limitation that remains poorly quantified. We assessed the combined effects of fallow duration and rainfall variability on soil organic matter (SOM) dynamics and microbial communities along a Sahelian rainfall gradient (453–644 mm) in western Niger. Three sites (Banizoumbou, Boyenga, and Tamou) and three land-use types were investigated: cultivated fields (15–20 years), young fallows (<3 years), and old fallows (10–15 years). We hypothesized that the benefits of fallowing would decrease under the driest conditions because of limited vegetation development. Fallow duration increased herbaceous biomass by two- to five-fold and enhanced plant diversity, with stronger responses at wetter sites. Old fallows contained twice as much SOM as cultivated fields, resulting in higher nutrient availability, cation exchange capacity, and water-holding capacity. Mid-infrared spectroscopy showed a shift in SOM composition from polysaccharide-rich to more condensed, humified carbon fractions. Old fallows also exhibited a ten-fold increase in bacterial abundance and a sixteen-fold increase in fungal abundance. Changes in microbial abundance, metabolic profiles, and respiration were most pronounced at the wettest sites. Overall, our results demonstrate that the restoration of soil fertility, carbon storage, and microbial functioning by fallowing is strongly controlled by both fallow duration and rainfall, suggesting that in hyper-arid zones, fallowing should be complemented with organic amendments to overcome biomass production limitations.
We describe a close relative of Spinosaurus aegyptiacus, the sail-backed, fish-eating giant from nearshore deposits of northern Africa. Spinosaurus mirabilis sp. nov., discovered in the central Sahara alongside long-necked dinosaurs in a riparian habitat, is distinguished by a scimitar-shaped bony crest projecting far above its skull roof. We discern three discrete phases in spinosaurid evolution. During the first phase with roots in the Jurassic, an elongate fish-snaring skull emerged that soon was modified along divergent paths. During a second Early Cretaceous phase, spinosaurids became the dominant predators in circum-Tethyan habitats. The final phase began just before the Late Cretaceous during the opening of the Atlantic Ocean, when spinosaurines attained maximum body size as shallow water ambush specialists limited geographically to northern Africa and South America.
Reliable modeling of heavy rainfall events is required for accurate flood prediction. This study evaluated the performance of the Weather Research and Forecasting (WRF) model in simulating heavy rainfall events that occurred on July 17, 2022 in the Sahelian region of Zinder in Niger. We performed a sensitivity study using various cumulus and microphysical schemes. We evaluated the reliability of the WRF model using different statistical approaches, including the probability of detection, false alarm ratio, success ratio, frequency bias, and critical success index. At the synoptic scale, atmospheric conditions were favorable for heavy precipitation in the Zinder region. Intense moisture transport from the southwest, high precipitable water values (>= 50 kg/m2), strong wind shear (10-15 m/s) and convective instability indicators (high K index and low convective inhibition) contributed to the initiation and intensification of convection. Outgoing longwave radiation (OLR) analysis confirmed the presence of strong convective activity and an active easterly wave, which strengthened the organization of convective systems. The evaluation analysis showed that the model effectively captured the spatial pattern of heavy rainfall in all ensemble member simulations. When combined with the Purdue Lin (PL), Morrison-2 moment (M2), and New Thomson (TS) microphysical schemes, the Tiedkte (TK) cumulus scheme outperformed other convective schemes. The WRF model has the potential to improve the prediction of heavy rainfall events in Niger and to inform decision-making processes.
Spontaneous fistulization of a gastric perforation to the skin is an extremely rare condition whose pathophysiology and etiology remain difficult to explain, especially since histological examination did not find any cancer cells. A-45 year-old male of Black African descent, residing in a rural area, was admitted to the General Reference Hospital with a spontaneous gastrocutaneous fistula. The history revealed the intake of nonsteroidal anti-¡inflammatory drugs for pain from a chronic foot wound. After imaging exploration (ultrasound, then computed tomography scan) proved noncontributory, an exploratory laparotomy confirmed a crater on the anterior surface of the gastric antrum leading to the skin, resembling a surgical gastrostomy; there was no mass or sign of peritoneal carcinosis. An atypical gastrectomy confirmed the benign clinical picture. The interest of this observation lies in its unusual character and encourages etiopathogenic research through the literature.
Monitoring environmental changes over time requires images with extensive historical depth. However, high spatial resolution images often lack such depth. This study investigates the impact of spatial resolution on image classification. Thus, Landsat 8 and Sentinel-2 images acquired between October and December 2020 were processed and classified using Random Forest regression on Google Earth Engine (GEE). This method allows for continuous land cover maps, required for robust assessment of land cover dynamics in patchy landscapes. A total of 1719 training samples were collected from the Collect Earth Online (CEO) platform to train the model. In addition to the spectral bands, vegetation indices were considered to optimize classification results. The study revealed statistical differences in land cover areas estimated by the two sensors. These differences are statistically significant at p < 0.001, although they are small. Validation results showed that the RMSE from Sentinel-2 is slightly lower than that from Landsat 8, with this difference significant at p < 0.05. Therefore, spatial resolution influences the accuracy of image classification. Nevertheless, given the observed differences between the two sensors, which ranged from 0.03% to 3.94% across land covers, Landsat imagery remains suitable for producing reliable land cover maps in heterogeneous landscapes.
