Nebkha development and its significance to wind erosion and land degradation in semi-arid northern China

Nebkhas (coppice dunes) are widely distributed in the agro-pastoral transitional zones of semi-arid northern China. Previous studies have suggested that they originated as a result of rapid desertification caused by extensive reclamations. However, our field investigations and analyses have shown that the origins of nebkhas are not closely associated with cultivation and land degradation, and their origin usually extend beyond the reclamation history of this region. Although the origins of nebkhas do not correlate with extensive reclamations, grassland reclamation has been found to accelerate the development and growth of nebkhas. Stratification and grain-size analyses have identified significant wind-energy fluctuations throughout the nebkha-building process, and records show that the strongest wind activities occurred between the mid-1960s and the mid-1980s. In addition, nutrient and grain-size analyses have revealed that grassland cultivation in semi-arid northern China has potential effects on regional land degradation. Nebkha formation, therefore, appears to be a good indicator of wind erosion and land degradation in semi-arid northern China. (c) 2005 Elsevier Ltd. All rights reserved.