Mu Us Desert advances

The sourthern fringe of the Mu Us Desert in Inner Mongolia has migrated some 200 km southward over the past 1,600 years with an average desertification speed of 126 meters each year. The discovery was made by a research group led by Prof. Li Chengsen from the CAS Institute of Botany in Beijing during its study on the ruins of the ancient city Tongwan in what is now Shaanxi Province. The researchers made this report in the August issue of the Journal of Palaeogeography. The ancient city of Tongwan, which was built from 413 to 418 A.D. on the north bank of Wudinghe River, used to be the capital of a Hun regime in ancient China. At present, the ruins are nesting in heartland of the Mu Su Desert with only sparse secondary shrub and grass communities. From the studies of plant remains from the walls of the ruined ancient city, the researchers found that about 1,600 years ago the Tongwan area was once a beautiful place taking shelter on the dry steppes with sparse forests. The local climate was temperate. Forests of Platycladus orientalis were distributed on the hills and uplands. Thermophilous trees grew along river banks and in gullies. Abundant aquatic plants grew in rivers, lakes and swamps while Salt-loving shrubs and herbs covered the salinized soil. However, the similar vegetative landscape endemic to the dry steppes has moved southward. In the course, the forests of Platycladus orientalis and forest steppe was forced to retreat to the southern part of the Yan'an area, which is about 200 km away. By using the co-localization analysis method, the scientists also estimate that its average annual temperature was 7.8-9.3ºC and its yearly precipitation averaged 403.4-555.0mm, roughly higher than today's corresponding figures by 0.2-0.7ºC and 60-100 mm respectively. It indicates that the climate in the Tongwan area about 1,600 years ago was slightly warmer and wetter than the present time. It is estimated that the Mu Us Desert migrated southward at a mean rate of 135 meters per year the past 1,600 years.