SUPERFICIAL RIEW ABOUT THE DESERTIZATION IN THE NORTH ZONE OF CHINA
Wu Zheng (Geography Department, South China Normal University, Guangzhou)
Based on the research carried out by the author for many years, the opinion about the desertization of arid, semi-arid and some semi-humid areas in the north zone of China is given in paper. It is considered that desertization is environmental formation or development of sand desert, and means a deteriorative process of ecological environments while a desert is the last or terminal result caused by the process, and means substantial existance of a geographic environment. Therefore, desertization can occur not only in "unorigional sand desert areas" but also in original sand desert areas, because of the extension and intensification of sand desert conditions. It is pointed out here why the desertization and sand deserts in the north zone of China have been changing since the Quaternary. The changes in geological periods of the Quaternary were caused by the climatic changes during the glacial periods and were a kind of "pure"' natural processes, i.e. a Kind of climate geomorphy processes; but the changes in human history belong to a kind of nature-mankind processes, i. e. climate-human action ones, which are mainly controlled by climatic conditions and are partly interfered by human economic activities. The author thinks that the sand deserts in the broad semi-deserts and steppes area in the east section of the north zone of China intermittently existed in the geological stages of Quaternary before the historical times and underwent several positive and negative changes, i.e. expansive and retractive processes or reviviscent and naturally stable ones. The desertization occurring in tiie hu-man history is still a developing stage in the long process of the sand desert. Since liberation, due to the climate keeping on a dry stage for one hundred years, the sharp increasing of the population and the effects from improper action in economic development, the desertization in the north zone of China, in a general view, has been still getting worse and worse. As a result, sand deserts have been expanding.