Field-Scale Aeolian Sediment Transport in the Sahel, West Africa

摘要

In the previous field-scale wind erosion studies in the Sahel, mass flux profiles, mass transport rates, and soil mass balance in the cultivated field and fallow land were estimated without measuring the mass flux at 0- to 0.05-m height where most soil particles are expected to move. We first addressed these deficiencies using a 3-yr field study in which mass flux at 0 to 0.05 m was measured directly with the Aeolian Materials Sampler (AMS) and then evaluated field mass transport rate, field soil loss, and fallow soil gain. We found that field mass transport rate, field soil loss, and fallow soil gain for each erosion event could not be estimated accurately without measuring the mass flux at 0 to 0.05 m. The field measurements of whole mass flux profiles revealed that (1) field mass transport rate at 0 to 1.0 m sometimes exceeded 40.0 g m(-1) s(-1), leaving pearl millet plants severely damaged, (2) field soil loss was 58 to 80 Mg ha(-1) (4-5 mm of topsoil) that was about 10% greater than those estimated without measuring the mass flux at 0 to 0.05 m using the AMS, and (3) fallow soil gain was 77 to 93% of the field soil losses. Results 2 and 3 implied that large amounts of soil were eroded from the field but that most sediment settled within about 5 m into the fallow. This finding provides useful information for the development of a countermeasure against wind erosion.