Correlation between nebkhas formation ability and silhouette layer parameters of desert plants

To determine why certain desert plants form nebkhas whereas others do not, we investigated common sand-fixing plants of the Minqin desert region, with 108 plants and nebkha samples set up at the edge of the above region. Measurement and comparative analysis of markers such as silhouette layer width, area, and center height revealed the following trends: (i) The silhouettes of nebkha-forming plants are triangular or cylindrical, i.e., the width of these silhouettes decreases with increasing height, and the silhouette centers are positioned 30 cm above the ground. Thus, these plants are shrubs. Plants that do not accumulate sand to form nebkhas are rhombus-shaped, and their silhouette centers are located more than 30 cm above the ground. (ii) Drifting sand flux and sandstorm particles are mainly concentrated in the region between 0 and 30 cm above the ground, explaining why plants with lower silhouettes can easily accumulate sand to form nebkhas. (iii) After being buried in sand, plants whose stems are capable of producing adventitious roots can form nebkhas/sand dunes dozens of times higher than the plant. Although other plants can still form nebkhas, the height of the produced dunes does not exceed the height of the plant. (iv) Silhouette area size is an important marker reflecting wind-breaking and sand-fixing ability, i.e., the ability of a plant to accumulate sand and form nebkhas. However, plants that cannot accumulate sand to form nebkhas, e.g., Haloxylon ammodendron, Calligonum mongolicum, and Artemisia desertorum also exhibit wind-breaking and sand-fixing abilities.