Tongwancheng,the capital of the Great Xia King dom during the period of Five Hu and Sixteen Kingdoms in the Chinese history，wa s situated on the north bank of Wudinghe River in the north of Jingbian County ，Sh aanxi ProvinceThe recent Tongwancheng area has a desert landscape,with only s parse secondary shrub and grass communit yHowever，about 1600 years ago the Tongwancheng area was once a beautiful plac e of dry steppes with the landscape of s parse forestThere was a temperate vegetation F orests of Platycladus orientalis were distributed on the hills and uplands Therm ophilous trees grew along river banks and in gulliesAbundant aquatic plants grew in rivers，lakes and swampsSaltloving shrubs and herbs covered the sali nized soilAt that time，the climate of the Tongwancheng area was as follows:t he annual mean temperature was 7.8℃～9.3℃，the hottest monthly mean tempe rat ure was 23.0℃～24.9℃ and  the coldest monthly mean temperature was -12.0℃ ～-5.6 ℃，the annual mean temperature difference was 28.5℃～38.2℃，the annual prec ipi tation was 403.4～550.0 mm，the monthly maximum precipitation was 83.8～123.9 mm  and the monthly minimum precipitation was 4.4～12.2 mmCompared with the pre sent c limate，the annual mean temperature and annual precipitation were respectively 0.2℃～0.7℃ and 60～100 mm higher It indicates that the clima te in the Tongwancheng area about 1600 years ago was slightly warmer and wetter th an the present timeThe similar vegetative landscape of dry steppes has moved southward  The forests of Platycladus orientalis and forest steppe have moved to the  southern part of Yan'an area It is estimated that the Mau Us Dese rt migrate d southward at a mean rate of 125 meters per year during the past 1600 yearsents in peat from Northeast China.Journal of Northeast Normal University,（4）：99～102