Grain-size characteristics of surface sediments of nebkhas at the southern margin of the Mu Us dune field, China

The grain-size characteristics of nebkhas are considered to differ from those of mobile dunes in relation to differences in vegetation influences. However, minimal research has been conducted in this respect. Therefore, this study investigates the grain-size characteristics of surface sediments of a nebkha field with 50%–80% vegetation cover at the southern margin of the Mu Us dune field. The grain-size composition and parameters were determined at different positions on nebkhas and in interdune areas. The results indicate that the nebkha sediments were significantly finer than those of mobile dunes, had weaker sorting, and were more positively skewed and more leptokurtic in relation to the interception of fine particles by vegetation, associated prevention of movement, and pedogenesis. We infer that the influence of pedogenesis resulted in minimal differences between grain-size compositions and parameters in samples obtained from different positions on nebkhas, between nebkhas, and in interdune areas. The creep populations of interdune sediments can be transported to the windward toe, but further transportation along the windward slope of a nebkha to the crest or leeward slope is limited because of vegetation interception.