MIDHOLOCENE CLIMATES AND ENVIRONMENTS IN CHINA

This paper focuses mainly on the climatic and environmental variations from 8.5 to 3 ka B.P. with particular reference to one stable warmer and wetter millennium (7.2-6 ka B.P.). Some large-scale centennial war ming was accompanied by an increase in precipitation owing to the expa nsion of the monsoon circulation, e.g. rapid warming during the period from 8.5 to 8.3 ka B.P. and was reflected in the high level of some i nland lakes and the sudden expansion of vegetation in pollen diagrams. The growth of the Neolithic culture with agriculture and settlement i n the present semi-arid area of Northwest China was undoubtedly relate d to the dramatic warming and wetting before 8 ka B.P. According to th e proxy data of palynological studies, the deviation of annual mean te mperature from today's about 7-6 ka B.P. was roughly estimated at abou t 1-degrees-C in South China, 2-degrees-C in the Changjiang (Yangtze) Valley, 3-degrees-C in North China and Northeast China. The strongest warming by 4-5-degrees-C was recorded in Oinghai-Xizang (Tibet) Platea u. The winter temperature rise was much greater than the annual averag e temperature. In the eastern half of China, the vegetation zones are mainly parallel to the latitude. During the climax of the Holocene war m period, the northern limit of the tropical monsoonal rain forest shi fted less than 1-degrees of latitude northward, the subtropical broad- leaved evergreen forest about 1-degrees of latitude, the north subtrop ical deciduous and evergreen broad-leaved mixed forest about 3-degrees of latitude in the coastal area but only 1-1.5-degrees of latitude in mid-West China and the warm temperate deciduous forest moved 4-degree s of latitude northward, greatly expanding its distribution. Further n orth, the cool temperate boreal forest withdrew from its southern boun dary by about 2-degrees of latitude. Global climatic warming in the mi d-Holocene resulted in a sea-level rise. During the period from 6 to 5 ka BP. the sea-level was about 1-3 m higher than the present level. L arge area of coastal lowland was submerged by sea water and frequency of occurrence of storm surges also increased during the high sea-level period.