51.91～37.96 Ka BP Vegetation Evolution Derived From A Peat Record In The Northwest Of Guizhou Province

The northwestern Guizhou is sensitive to climate change and has a fragile ecological environment.It is important for protecting vegetation in the area to explore and understand the vegetation evolution and climate change.In this study,350-cm of DF-2 core from Dafang peatland in northwestern Guizhou was selected as the research material.Based on AMS ¹⁴C dating results and sporopollen charcoal analysis,the analysis of water content,dry bulk density,loss on ignition,carbonate content and humification.The paleoecology evolutionary of the MIS3 stage（51.91～37.96 cal.ka BP）was reconstructed in Dafang region.Combined with the power spectrum analysis,wavelet analysis of the pollen time sequence and the results of the previous results,the driving mechanism of the MIS3 stage climate and environmental change in northwestern Guizhou is explored,and the response process of vegetation to paleoclimate change is clarified.The main findings are as following:（1）The evolution history of vegetation in the MIS3 stage of the Dafang area is:51.91～47.78 cal.ka BP,the deciduous and evergreen broad-leaved forest mainly based on Fagus,Deciduous-Quercus,Evergreen-Quercus,and Carpinus;47.78～44.89 cal.ka BP,the deciduous and evergreen broadleaved forest dominated by Cyclobalanopsis,Evergreen-Quercus,Deciduous-Quercus and Fagus;44.89～44.18 cal.ka BP,the shrub tussock with sparce trees,such as Deciduous-Quercus,Corylus,Ericaceae and Gramineae;44.18～39.07 cal.ka BP,the evergreen and deciduous broadleaved forest dominated by Cyclobalanopsis,Evergreen-Quercus,Deciduous-Quercus and Fagus;39.07～37.96 cal.ka BP,the shrub tussock with sparce trees,mainly based on Corylus,Ericaceae and Gramineae,etc.（2）The climate change in the MIS3 stage of Dafang area experienced 5 stages:51.91～47.78 cal.ka BP,in this period,the climate of Dafang experienced a transition from slightly warm and wet to warm and humid;47.78～44.89 cal.ka BP,the climate was cooler and more humid;44.89～44.18 cal.ka BP,it was Heinrich 5,the climate is cold and slightly dry in Dafang area;44.18～39.07 cal.ka BP,the climate in the Dafang area is restored to warm and humid;During Heinrich 4 at 39.07～37.96 cal.ka BP,the temperature decreased,and the humidity also decreased,the climate was cold and dry.（3）Through the power spectrum analysis and wavelet analysis of PCA1 and PCA2,indicated that the climate change of Dafang area was mainly controled by the amount of ice and solar insolation in the northern hemisphere.At the same time,it can be found that the Dafang has the similar cycles with other area,they have the same climate condition.（4）The evolution of vegetation in Dafang areas during MIS3 stage is closely related to climate change.Influenced by climate change,vegetation in Dafang region is mainly manifested as the alternate evolution of the evergreen and deciduous broadleaved forest and shrub-grass.