Performance of the Main Materials Used in Dune Stabilization in the Sahel, Niger

Abstract

Dune fixation is one of the most effective ways of combating sand encroachment in the Sahel. However, the specific role of the materials used in dune stabilization and vegetation recovery remains poorly documented. In this study, the performance of the main fixation materials, Leptadenia pyrotechnica branches and Hyphaene thebaica rachis, was assessed through an experimental setup over two seasons (2014-2015) on an active dune field. Three common combinations were tested: windbreak fences made from L . pyrotechnica branches (P LP), windbreak fences made from H . thebaica rachis (P RHT), and windbreak fences of L . pyrotechnica branches combined with a paving of H . thebaica rachis (P LP/RHT). On average, 10 branches of 650 g ± 6.8 g are needed to erect one linear meter of P LP at 1.7 m in height (average porosity: 18.4% ± 1.2%), and 29 rachis of 227.7 g ± 0.57 g for one linear meter of P RHT at 1.4 m (initial porosity: 18.45% ± 4.74%). The paving requires about 6 rachis per square meter. In 2014 and 2015, these installations allowed for the collection of 1080 kg∙m − 1 and 940 kg∙m − 1 of wind-blown sediments, respectively, at −5 m from the first windbreak fence. Reductions in wind-blown sediment flux at 15 m downwind reach 96.18% for P LP/RHT, 93.91% for P LP, and 90.67% for P RHT, compared to the flux measured at 5 m upwind. After the first rainy season, the highest dry biomass yield was recorded with P LP/RHT (322.90 kg/ha ± 102.04 kg/ha), followed by P LP (213.98 kg/ha ± 82.20 kg/ha) and P RHT (132.93 kg/ha ± 59.11 kg/ha). The installation of these windbreak fences promoted improved seed retention, reduced aeolian flux, enhanced soil surface stability, and created a microclimate more conducive to seed germination and the development of herbaceous vegetation.