陕西榆林和河南洛阳地区4 ka BP前后聚落演化差异及其古气候原因

陕西榆林和河南洛阳地区44 Ka BP前后聚落密度统计表明，44 Ka BP之前的龙山时期，两地区人类文化均得到充分发展，区域聚落密度位于中国同时期前列。44 Ka BP之后的夏商时期，洛阳地区聚落密度进一步增加，而榆林地区人口和聚落密度锐减，人类文化呈现明显的衰落趋势。由于地理位置的差异，两地现代年平均降水量相差约200mm。榆林地区人类活动区域主要为黄土丘陵地貌，有限的河流水资源难以利用，旱作农业主要依赖降水。洛阳地区降水丰沛，且盆地平原区可以便利地利用河流水资源，降水波动对区域文化发展影响较小。古气候研究表明，44 Ka BP前后存在1次重要的全新世气候干凉化事件。该事件之后，洛阳地区的年平均降水量大约从650mm降至500mm，仍高于旱作农业所需最低降水量，因而人类文化仍得到进一步发展。榆林地区的年平均降水量大约从450mm降至350mm，由半湿润气候转变为半干旱气候，导致主要依赖降水的旱作农业难以为继。两地区地理位置和环境特征的差异是影响各自文化演化的基础因素，44 Ka BP前后的气候干凉化事件是导致两地文化演化产生两种不同结果的直接原因。

Difference and its palaeoclimate reason of settlement evolution between Yulin area of Shaanxi Province and Luoyang area of Henan Province around 44 Ka BP

We analyzed the change of settlement density in Yulin area of Shaanxi Province and Luoyang area of Henan Province around 44 Ka BP. The culture of these two areas were both well developed during the period of Longshan (before 44 Ka BP) and the settlement densities of the two areas were on top of the list in China at that time. The further increase of the settlement density occured in Luoyang area during the period of the Xia and Shang Dynasties (after 44 Ka BP), but the density of population and settlement declined sharply in Yulin area after 44 Ka BP，which obviously reflected the decline of the culture. According to the geographical position differences，the mean annual precipitation in Luoyang area is 200mm higher than Yulin area. The landform of the loess hills is the main human activity place in Yulin area，where the limited water resource of river is not easy to be used. The development of dry farming mainly depends on the rainfall. The rainfall is abundant in Luoyang area and human beings can conveniently use river water resources in basin plain. So the fluctuations of the rainfall cannot influence the development of dry farming. The study of palaeoclimate showed that there was a significant climate event around 44 Ka BP. After this climate event，the mean annual precipitation declined approximately from 650mm to 500mm in Luoyang area. But it was still higher than the minimum precipitation that dryland farming needed. So the human culture could develop much further. The mean annual precipitation declined approximately from 450mm to 350mm in Yulin area，which made the climate change from sub-humid to semi-arid. The climate change made dryland farming cannot develop further. This study proves that the differences of the geographical setting and environmental characteristics between the two areas are the basic factors that affect their respective cultural evolution. The climate event around 44 Ka BP is the direct driving factor that leads to two different results．