近2000年来长江上游荔枝分布北界的推移与气温波动

通过对近2000年来长江上游荔枝分布北界变化的讨论,说明长江上游荔枝种植北界最北可达北纬31°40’,近2000年来荔枝种植的北界总的来看是逐渐向南退缩；两晋、南北朝时期和唐后期的寒冷气候在长江上游地区反映不太明显,而南宋12世纪的寒冷气候在长江上游反映十分明显,这说明12世纪的寒冷气候是长江上游近2000年来最寒冷的时期；在12世纪中长江上游又以70年代最为寒冷。

THE MOVEMENTS OF THE NORTHERN BOUNDARY OF LITCHI DISTRIBUTION AND FLUCTUATIONS OF TEMPERATURE IN THE UPPER REACHES OF THE YANGTZE RIVER IN THE PAST 2000 YEARS

The upper reaches of the Yangtze hiver lies in the middlelow latitude ofNorthern Hemisphere. The climatic variation was not remarkable during Han Dynasty.The northeastern boundary of the type of litchi economic distribution during TangDynasty was almost 2 latitude northeastwards coamparing with that of the present. Asannual mean temperature of litchi growing requires temperature of above 18℃, so theannual mean temperatUre of Chengdu, Leshan etc, was above 18℃ at that time,which was about 1-2℃ higher than present.The distribution of litchi in the upper reaches of the Yangtze River during SongDynasty had already reached 31°N in the eastern region and about 30°N in the west.On the whole, the northern boundary of litchi planting during Tang and Song Dynastyhadn' t greatly changed in the upper reaches of the Yangtze hiver. According tohistorical materials, the cold climate during Southern Song Dynasty in the twelfthcentury was proved by the change of litchi distribution in the upper reaches of theYangtze River.The records of historical documents indicate that the Three Gorges of the Yangtzehiver experienced very cold temperature from 1170 to 1 172. But the cold climate ofSouthern Song period had a minor effect on litchi growing in the region of 29°N orlower in the upper reaches of the Yangtze River.During the Little Ice Age, the cold climate was very obvious in the upper reachesof the Yangtze caver which can be deduced from the migration of litchi distribution.During the period of Ming and Qing Dynasty, the northern boundary of litchi hadmoved southward and reached the region of 29°30' N or lower.Studies suggested that the temperature began to rise from the twentieth century.Although today the northern boundary of litchi in the upper reaches of the YangtZeRiver can reach Wuling Town in Wanxian County at 30°30’ N.Considering the migrations of litchi planting distribution in the upper reaches of theYangtze hiver in the past 2000 years, the climatic fluctuations in the upper reaches ofthe Yangtze caver reconciled with national climatic fluctuations, such as the warm andhnmid in Tang Dynasty, the cold period of Southern Song Dynasty in the twelfthcentury, the warm climate of Yuan Dynasty, and the cold climate of Ming and QingDynasty, etc.According to the changes of litchi distribution in the upper reaches of theYangtze River, 1170's was the coldest period, the colder period is the Eastern Jin,Southern and Northern Dynasty. The low temperature in the farer Tang Dynasty wasn'tremarkable in the upper reaches of the Yangtze River. The cold climate of SouthernSong Dynasty was very obvious, which indicate that the cold fluctuations of two-Jin,Southern and Northern Dynasty and the later Tang dynasty were much smaller thanthat of Southern Song Dynasty.