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Journal of Desert Research ›› 2026, Vol. 46 ›› Issue (2): 11-23.DOI: 10.7522/j.issn.1000-694X.2025.00058

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Morphology and sediment grain size of Caragana tibetica nebkhas in the Gonghe Basin

Yue Li(), Xuemeng Hao, Fengjun Xiao(), Weige Nan, Guangyin Hu, Yili Shang, Lijie Wang   

  1. School of Geography and Tourism,Shaanxi Normal University,Xi'an 710119,China
  • Received:2025-03-31 Revised:2025-04-25 Online:2026-03-20 Published:2026-04-13
  • Contact: Fengjun Xiao

Abstract:

Sand source serves as the material basis for nebkha formation. In the desertified steppe of the Gonghe Basin, this study focused on Caragana tibetica nebkhas in different sand supply: a downwind quicksand belt at one flank of barchan dune, and in its adjacent desert steppe without quicksand parallel to the dominant wind direction. Morphological parameters of nebkhas were measured, and surface sediment samples were collected to analyze the evolutionary patterns of Caragana tibetica nebkhas morphology and sediment grain size characteristics in response to varying sand supply. Key findings include: (1) Stable sand input in quicksand belt promoted vigorous growth of Caragana tibetica, forming shadow dunes in the developmental stage; in desert steppe, sand scarcity led to Caragana tibetica senescence, resulting in semi-ellipsoidal nebkhas in the stage of stabilization to recession. There was a significant correlation among the morphological parameters of nebkhas and shrub height emerged as the dominant morphological driver. Morphological parameters except for the short axis significantly increased with sand supply (P<0.05), confirming sand availability as the primary control on Caragana tibetica nebkha dimensions. (2) In the quicksand belt, the significant linear relationship between the short axis length and the elongation of shadow dunes revealed the dominant control of short axis length over the extension of shadow dunes Under the influence of wind fetch effects, the length, bottom area, and volume of shadow dunes in the quicksand belt reached their maximum values at 30-60 m downwind of quicksand belt at the flank of the barchan dune. (3) The surface sediments of Caragana tibetica nebkhas in both the quicksand belt and desert steppe are dominated by medium and fine sands, with bimodal grain-size distributions, and saltation as the primary transport mode, but the desert steppe showed a significant increase in suspension components. Differences in sand supply led to distinct sedimentary characteristics: In the quicksand belt, medium sand content increased, silt and very fine sand fractions reduced, exhibiting a narrower kurtosis, a coarser mean grain size (1.88 Φ vs. 2.32 Φ) and better sorting.

Key words: nebkha, sand supply, Caragana tibetica, morphological characteristics, sediment grain size characteristics

CLC Number: