Distribution and Characteristics of Nitraria sphaerocarpa nebkhas in a Gobi habitat outside an oasis in Hexi Corridor region, China

Nitraria sphaerocarpa Maxim., a typical desert plant which often appears in nebkha form, is widely distributed along the periphery of oasis in arid regions of Northwest China, and plays an important role in desertification control around oases. In this paper, the characteristics and distribution patterns of N. sphaerocarpa nebkhas were investigated in a Gobi environment outside an oasis. Results shows that about 200 N. sphaerocarpa nebkhas per hectare was recorded and total sand sediments was 25 m³/ha. Nebkhas vary in size, and the mean height (H) and horizontal composition (L) were 15 cm and 80 cm, respectively. There exists a significant linear relationship between H and L, suggesting that the investigated nebkhas are mostly in the growth stage. The numbers, height and sand deposit of nebkhas decreased with increasing distance away from the oasis. Grain-size analysis indicates that the mean grain size of sediments at the crests of nebkhas increased with increasing nebkha height. Organic C and total N concentrations were related to the mean grain size. It was concluded that N. sphaerocarpa shrubs are efficient horizontal sand traps for wind-driven sediments. A better understanding of the development of nebkha can provide information for the design of biological sand control measures around oases in arid regions.