11.4~3.5 Ka BP Vegetation And Climate Dynamics Derived From A Peat Record In The Southwest Of Guizhou Province

Guizhou Province is located in the hinterland of Yunnan-Kweichow Plateau,with widespread karst landforms and fragile ecological environment.It is very sensitive to climate and environmental changes.Therefore,Guizhou Province is an important area to study paleoclimate and paleoenvironment conditions.In this paper,350 cm of AL18core are selected as the research material,the main components of the borehole are bluish gray lacustrine sediments and near black peat.Based on high-resolution AMS¹⁴C dating and sporopollen charcoal analysis,the detemination of TOC,TN,water content,dry bulk density,and the geochemical element content and chroma,the evolution history of 11.4?3.5 cal.ka BP was reconstructed in Anlong area.Based on the results of wavelet analysis and power spectrum analysis,the driving mechanism of paleoclimate and paleoecology changes were explored.The main results are as following:(1)Stage I,11410?10580 cal.a BP,the thick growth of grass with sparse forest dominated by Polypodiaceae,Osmunda and Pinus;Stage II,10580?10030 cal.a BP,the coniferous and broad-leaved mixed forest dominated by Pinus,Cyclobalanopsis,Quercus,Castanopsis,with a lot of grass;Stage III,10030?8680 cal.a BP,the coniferous and broad-leaved mixed forest dominated by Pinus,Cyclobalanopsis,Quercus and Castanopsis;Stage IV,8680?4830 cal.a BP,a mixed forest dominated by evergreen broad-leaved trees such as Cyclobalanopsis and Castanopsis;Stage V,4830?3500 cal.a BP,the coniferous and broad-leaved mixed forest dominated by Pinus,Cyclobalanopsis,Quercus,Castanopsis.(2)11410?10580 cal.a BP,the Anlong area was in the transition stage from the Younger Dryas event(YD)to the early Holocene,the climate was cold and dry;10580?10030 cal.a BP,it has entered the early Holocene,but it is still relatively cold and dry;10030?8680 cal.a BP is in the late interval of early Holocene,the climate has become warmer and humid,it is the wettest period of the study;8680?4830 cal.a BP was during the middle Holocene warm period,the temperature was at the highest stage of the study period,the climate was warm and humid;4830?3500 cal.a BP was the late Holocene,the climate changed from warm and wet to cold and dry.In addition,cold events of 11 ka BP,10.3 ka BP,9.5 ka BP,8.1?8 ka BP,7.2 ka BP,6.5 ka BP,5.6 ka BP,4.1 ka BP can be clearly recorded in Anlong peat.The above results were similar to many records from the Indian monsoon region in southwestern China.(3)Through wavelet analysis and power spectrum analysis of PCA1 and PCA2,indicated that the climate change of Anlong area were affected by atmosphere-ocean system of the earth and the solar activity outside the earth.At the same time,it can be found that the Yunnan-Kweichow Plateau was significantly affected by the Indian monsoon,and the driving mechanism of its climate evolution was similar in Indian monsoon-dominated area,and similar cycles can be found in the records from this area.(4)The process of vegetation evolution was closely related to climate change.Across compared the reconstruction results of vegetation dynamics in many areas of the Yunnan-Kweichow Plateau,it is found that the response relationship of vegetation to climate changes was generally reflected in the thermal conditions in large areas.With the climate variations,the vegetation successions in Anlong area mainly manifested by the distribution scope and area of Pinus forest and evergreen broad-leaved forest,and the vegetation species show the alternation of cold-loving and warm-loving plants.