Sandy Desertification For Sandy Lands In Northeast China Throughout The Last 2000 Years

In this study,we compiled a large number of aeolian sand and paleosoil ages from stratigraphic sections and synthesized the data in order to reveal sandy desertification(SDN)processes in sandy lands of northeast China throughout the last 2000 years.Based on this,the relationship between SDN processes and climate change and human activities was analyzed,and the causes of modern SDN reversal and future trends were discussed.(1)SDN in sandy lands of northeast China has experienced three reversals and three expansions since the last 2000.Our results indicated that from 0 to 210 CE,from 770 to 1050 CE,and from 1170 to 1440 CE,three SDN reversals took place in these deserts,whereas three SDN expansions were found from 210 to 770 CE,from 1050 to 1170 CE,and since 1440 CE.The first and third SDN reversals caused considerable paleosoil development in these deserts from 0 to 350 CE and from 1230 to 1660 CE,respectively.However,extensive aeolian sand accumulation has taken place from 350 to1230 CE and since 1660 CE due to the first and third SDN expansions,respectively.Therefore,the modern landscape for sandy lands of northeast China formed over the last 300 years.(2)Since the last 2000 years,the first,second and third SDN reversals in sandy lands of northeast China have all been caused by warm and humid climate;the first and second expansions were all caused by cold and dry climate;the early third expansion is controlled by cold dry climate;the middle term was caused by cold and wet climate and irrational human activities;the later period was entirely attributed to irrational human activities.(3)Under the warm and humid climate background,as long as the human activities reduced,the vegetation in the sandy lands of northeast China can restore naturally.Therefore,it is not reasonable for the SDN reversal in sandy lands of northeast China since 1980 s has been entirelyattributed to the artificial vegetation restoration project.Under the background of continuous warm and humid in twenty-first century,SDN will continue to reverse in sandy lands of northeast China and even the whole northern China as long as human activities reduced moderately.