Research On The Influence Of Sui-Tang Warm Period And Its Transition On The Rise And Fall Of The Tubo Dynasty

Tubo Dynasty or Tubo Empire is the one of most powerful governments in Tibet's history,which has had a profound impact on the entire Tibetan Plateau(TP)and its surrounding areas.Therefore,the reasons for its rise and decline have always been an important subject of widespread academic research.Traditionally,internal factors such as economic,religion,politics have been used to explain the rise and fall of this dynasty,these causes are difficult to interpret the timing of the vicissitudes of this regime.With the rapid progress of accurately-dated and highly-resolved past climate reconstruction and the observations of synchroneity between climate change and societal variations,scholars tend to invoke climate change to explain the rise and fall of ancient civilizations,empires,or dynasties,however,the possible role of climate change in the vicissitudes of Tubo Dynasty has been remained poorly investigated.This research systematically studied the reasons for the rise and fall of the Tubo dynasty from the perspective of climate change.First,the paleoclimate reconstruction in the past few decades,especially those based on historical document,was used to provide climate background across the rise and fall of Tubo dynasty;Second,the key factors affecting the growth of crops on the TP were identified,and a niche model was established;Third,the impact of climate change during the SuiTang Warm Period and its transitional interval on agricultural yields and the variations in agricultural planting areas were analyzed;In the end,on the basis of the above research,the causal paths from climate change to the economy,military,religion and politics,and to the rise and fall of the Tubo dynasty were established.The main results are as follows:(1)During the Sui-Tang Warm Period(601-820 AD),the temperature rose and precipitation increased;after the Sui-Tang Warm Period(821-920 AD),the temperature dropped and precipitation decrease.The Sui-Tang Warm Period and its transition have obvious correspondences in many parts of the world,and the motivation may be related to changes in the temporal variation of reconstruct total solar irradiance.(2)The rise and fall of the Tubo Dynasty corresponded well in timing with the Sui-Tang Warm Period and its transition to little ice age.The climatic conditions in the warm period provided favorable climate which would increase the yield per mu of highland barley,elevated the planting altitude of highland barley and thus expanded its cultivated area.In contrast,the adverse climatic conditions during the subsequent Sui-Tang transitional period would reduce yield per mu and the cultivated areas of highland barley.The niche model showed that such climate transition would reduce agricultural area by about 21.66%.(3)Although there are many factors affecting the rise and fall of this dynasty,climate change is probably one of the most important and ultimate factors that cannot be ignored.In 601-820AD,suitable climatic conditions during the Sui-Tang Warm Period increased the total output of agriculture and animal husbandry,provided manpower and material resources for the rise,development,and sustained expansion of the Tubo dynasty for more than two hundred years.In contrast,the climate deterioration after the Sui-Tang Warm Period around 820AD shook the economic foundation of the Tubo Dynasty,and then further stop military expansion,stimulated social conflicts,triggered the peasant uprisings and the Buddhism extermination,which combined to became important factors in the decline of the Tubo dynasty.This study tried to introduce the niche model to establish the intermediate link between the climate change impact and the vicissitudes of Tubo Dynasty,and then proposed alternative explanation for the sudden rise and fall of the Tubo dynasty.The results of this study are helpful to provide an insight into the causes and mechanisms behind the rise and fall of the Tubo dynasty;Since the Sui-Tang Warm Period has been regarded as an important historical analog for the 20th century and future warm period,the results of this study can also provide useful reference for human to adapt to future warming climate.