This can be seen, in particular, in the Huihe region of Hulun Buir steppe where the natural condition is better than other sandy areas. The desertified land has been transformed into woodland of Pinus sylvestris. The development trend of desertification according to three landuse types in north China in recent years is summed up in Figure 2 . From this analysis we can conclude that although the desertified area of some localities has been reduced since 1975, as a whole, desertification is still a spreading trend. In the rehabilitation of desertified land, protection should first be given to threatened productive desertified land, otherwise desertification will be exacerbated and will result in great economic loss.
Desertification caused by water erosion is also very severe.
Therefore it is very important to find different ways to bring the different types of desertification under control. On the basis of this work, and over many years, we have developed a model for rehabilitation of desertified land which combines experimental, demonstration and popularization processes. 2 Measures should be suited to local conditions. Protective networks should be established in oases and windbreaks of trees and shrubs should be set up around the oases. The structure of landuse in drylands should be readjusted and the carrying capacity should not be overtaxed by grazing.