AEOLIAN ACTIVITIES IN SEMI-ARID CHINA: COMBINING MODERN ECOLOGICAL PROCESSES WITH PALEOECOLOGICAL EVIDENCE

The frequently occurred dust storms in northern China have attracted scientists not only from China, bust also from Korea, Japan and even North America, due to their long distance transportation. The semi-arid region in northern China has been undergoing strong desertification, particularly in recent 50 years. Has vegetation degradation contributes a lot to dust storm outbreak? Under what climatic and vegetational conditions did aeolian activities occur? How to distinguish the nature processes from anthropogenic ones in desertification? In our study, we try to give answers to the above scientific problems. We first study modern ecological processes with data of vegetation survey and soil analysis. Then combining paleoecological data, such as pollen, macro-fossil, physical and chemical characteristics of four lake sediment sequences, we reconstructed the climatic changes, vegetation development and aeolian activities during Holocene in some selected key area in semi-arid China. The vegetation index (NDVI) from NOAA AVHRR data and intensity of dust storms are positively correlated, indicating that vegetation cover contributes to dust storm outbreak. 8 landscape types were further distinguished in a key study area in southeastern Inner Mongolia Plateau. In was demonstrated that the degrading typical steppe on stony mountains and cultivated land have the highest possibility of dust release. In contrary, moving dunes has low content of fine dusts and release little dusts in per unit area. The fixed sand dunes, lowland vegetation and meadow steppe also contributes little to dust storms due to their high vegetation cover. It was demonstrated that the aridity has been increased since 5900 a B.P. in semi-arid China. The transition from humid to an arid climate coincided with enhanced aeolian activity, and deciduous woodlands were replaced by pine woodlands and then by steppe in response to the climatic deterioration. Climatic changes are key driving factor for desertification and further aeolian activities in se