Evolution Of Human Activity Intensity In Hehuang Valley In The Past 2000 Years And Analysis Of Influencing Factors

The intensity of human activity is the result of the comprehensive action of natural environmental conditions and human social and economic activities.Since humans entered the agricultural society,agricultural utilization activities have led to local and even global environmental changes by changing the original land cover,and this influence will continue to expand and strengthen with the development of the society.The impact of human activities on the earth system has a cumulative effect.Therefore,exploring the change in the intensity of human activities is helpful to deepen the understanding of the core proposition of geography--the relationship between man and earth.Hehuang Valley is located in the northeast of Qinghai-Tibet Plateau.Because of its superior natural environment,Hehuang Valley has become one of th-e areas with high concentration of population,cultivated land,settlements and t-raffic routes.In addition,this region is a transitional region between Qinghai-Tibet Plateau and Loess Plateau,agricultural and pastoral areas,monsoon and non-monsoon areas,and human activities are significantly affected by climate c-hange.Therefore,it is a typical case area for human activities research in a l-ong time scale.Taking Hehuang Valley as the research area,the population,c-ultivated land,total settlement and traffic information were estimated and revise-d by collecting and sorting historical documents.The population,cultivated lan-d,settlement and traffic distribution of five periods in Hehuang Valley during the historical period were reconstructed.Based on the reconstructed indexes of population,cultivated land,settlement and traffic,the human footprint model was constructed to estimate and deduce the intensity of human activities in He-huang Valley in the past 2000 years.The main conclusions are as follows:(1)In the past 2000 years,the cultivated land,population,settlements and roads in the Huangshui Valley were mainly distributed in the lower elevation areas near water sources along the Huangshui River and the Yellow River.The distribution of population and cultivated land in Huangshui Valley is dense,while the Yellow River Valley is sparse.The intensity of human activities in Huangs-hui Valley is greater than that in Yellow River Valley.(2)In the past 2000 years,human activities were stronger in Xining Basin,Le-du Basin,Minhe Basin,and GUI De Basin,Xunhua Basin and Hualong Basin in the Huangshui Valley.These areas are relatively flat,soil fertility and wate-r storage is good,suitable for agricultural production,human activity intensity is greater;At the same time,the intensity of human activities experienced the process of expanding from Huangshui Valley to Yellow River Valley.(3)In the past 2000 years,the intensity of human activities in Hehuang Valley has experienced a change from weak to strong.Due to the low proportion of agricultural economy and limited population,the intensity of human activities was the weakest in the Han Dynasty.After that,it went through operation and development in the Tang,Song and Ming dynasties,and until the Qing Dyna-sty,the scale of cultivated land reclamation,the degree of population gathering and frequent human interaction in Hehuang Valley.It was the strongest in history.(4)In the past 2000 years,human activities in Hehuang Valley have been grea-tly affected by climate change,natural disasters,wars,policies and other facto-rs.There is a significant correlation between the cold and warm fluctuations of climate and the intensity of human activities.The intensity of human activit-ies increases in the warm period and vice versa in the cold period.Natural di-sasters indirectly affect the intensity of human activities in the region,and lea-d to the change of the intensity of human activities through the influence of r-egional population and cultivated land area.The immigration policies of the g-overnments in different periods are the main external driving force for the inte-nsification of human activities in Hehuang Valley.The population and agricult-ural technology brought by the long-term immigration policy in the history ha-ve greatly promoted the intensification of human activities in Hehuang Valley.