Supporting dataset for the article "Re-Greening the Sahel? Evaluating Tree Cover Restoration Strategies in Niger"

This dataset was collected as part of a study on the effectiveness of land restoration techniques in the Illèla municipality (Tahoua region, Niger). The study focused on two villages—Guidan Karo and Nadara II—situated between 14°22′00″ and 14°28′60″ N, and 15°16′60″ and 15°19′00″ E. Illèla is located in the Sahelo-Sudanian climatic zone, with annual rainfall ranging from 300 to 1,020 mm (mean: 478 mm) and average annual temperatures of about 28.5°C. Agriculture and livestock are the main livelihood activities, and the municipality has been a priority area for soil and water conservation (SWC) interventions. In recent decades, large areas of degraded land in Guidan Karo and Nadara II have been rehabilitated using SWC structures combined with tree planting. These restoration activities vary depending on the presence or absence of project support, particularly regarding site monitoring and maintenance. Methodology Field data were collected between February and March 2023 across nine restored sites: six in Guidan Karo and three in Nadara II. Among these, seven sites were managed with project support (guarding, upkeep of structures, plantation care, and replenishment), while two were unmanaged (no monitoring or maintenance). The sampling strategy included: Nine restored sites, incorporating five types of SWC structures (coded 1–5):1 = Trenches2 = Stone bunds + trenches3 = Stone bunds4 = Half-moons5 = Bench terraces 44 inventory plots of 2,000 m² each (100 × 20 m). Five plots were surveyed per site, except at the CSE site where only four were established. Transects were oriented East–West or North–South depending on local topography and accessibility. Within each plot, all planted individuals were recorded. The following variables were measured or noted: Tree diameters: DBH (130 cm above ground) and Db (20 cm above ground) Species identity Type of SWC structure Geomorphological unit of the site (coded: slope = 1, pediment = 2, plateau = 3) Geographic coordinates Management status (with = 1, without = 0) In total, six woody species were inventoried, representing the families Fabaceae and Rhamnaceae: Vachellia seyal, Senegalia senegal, Acacia nilotica, Acacia raddiana, Bauhinia rufescens, and Ziziphus mauritiana. Data Structure The dataset is provided as a .csv file with 1,564 observations and 9 variables: village: Name of the village (Nadara II or Guidan Karo) plot: Plot identifier (e.g., CSE-1, GK-2, etc.) species: Scientific name of the planted tree species Diam: Diameter (cm) at the position of measurement (POM) age: Age of the plantation in months SWC: Type of soil and water conservation structure (1–5, see above) management: Management status (1 = monitored/maintained, 0 = unmanaged) geomorphology: Site geomorphology (1 = slope, 2 = pediment, 3 = plateau) POM: Position of measurement (20 = diameter at 20 cm above ground; 130 = diameter at breast height, DBH) This dataset provides a baseline for assessing the performance of different SWC structures, plantation strategies, and management regimes in semi-arid restoration contexts. It is intended to support research on land rehabilitation, vegetation dynamics, and ecosystem service recovery in the Sahel.