Nebkha dune morphology in the gobi deserts of northern China and potential implications for dust emission

Nebkhas (coppice dunes) have formed throughout the gobi desert regions of China in response to the decreased near-surface wind speed caused by vegetation, combined with deposition of aeolian sediment in and around the vegetation. Although nebkhas have been extensively studied on several land surfaces, they have not yet been fully described where they form in areas of gobi desert. Based on field investigations of nebkha morphology and adjacent land surface sediment content on and inside the surface of these dunes, the following were found: (i) the nebkhas that develop in gobi deserts consist of two types - dunes with or without a depositional tail (a shadow dune); (ii) the nebkhas in the area of gobi desert were smaller than those found in sandy deserts, oases, or other areas with a rich sediment source, with a mean height of 0.28 m, mean width 1.63 m and mean length 1.34 m; and (iii) the dune height, length and width were significantly positively linearly related to the vegetation height, length and width. These patterns were similar at all four of the study sites, but the relationships with dune width differed among the sites. The average particle-size distributions on and inside the vegetation did not differ between the four sites. However, significant spatial differences in the sediments on and inside the dunes indicate that nebkhas can capture both local and distant sediments driven by the wind. These findings suggest a potential role of nebkhas in dust emission, although this role must be confirmed in future research.