Phytolith Record Of High Resolution Climate Change In Gushantun Peatland Since Late Glacial Age

The Northeast China is located in the eastern edge of the Eurasia and close to the Pacific Ocean.The NE is a sensitive area reflecting climate change which belongs to the EASM?East Asian Summer Monsoon?affected area.Peatland was widely development because of cold-wet climate in NE.The peatland contains abundant paleoenvironment information,providing a reliable high-resolution paleoenvironment record.In this paper,we sampled the7.5m Gushantun peatland profile with 1cm segmentation,and AMS¹⁴C dating and phytolith analysis were performed to obtain phytolith sequences since 13.0 cal ka BP.The MAT?Mean Annual Temperature?and MAP?Mean Annual Precipitation?sequences of the Gushantun peatland were reconstructed by the qualitative,semi-quantitative and quantitative reconstruction of phytolith,and the climate cycle of MAT and MAP in Gushantun peatland was discussed through spectrum analysis.On the basis of the previous research about the EASM,we discussed the reliability of reconstruction of the EASM evolution by using the phytolith since 13.0 cal ka BP.The main conclusions are as follow:1.32 types of phytoliths are observed in Gushantun peatland profile.Some sponge spicules and diatoms are also founded.The phytolith analysis result shows that the phytoliths are mainly from herbaceous and woody plants.The grass phytolith are mainly from Pooideae,Chloridoideae,Panicoideae.The result of phytolith assemblages,warmth index and PCA-F1scores show that the paleoenvironment was cold and wet during 13.0-11.1 cal ka BP,then turned warm and wet during 11.1-6.5 cal ka BP,the climate turned dry during 6.5-2.1 cal ka BP and turned dry and cool from 2.1 cal ka BP to present.2.The MAT and MAP variation of Gushantun peatland were reconstructed by phytolith-temperature index function and the phytolith-precipitation transfer function in NE.The results comprehensively show the millennial to centennial climate change processes and events recorded by the GISP2 ice core?¹⁸O and the North Atlantic ice records,including the YD,the transition from the Late glacial to the Holocene,8.2 ka and 4.2 ka event and the MWP and LIA are also reflected.3.The spectral analysis of MAT and MAP sequence of the reconstruction shows that the climate change in Gushantun peatland has 6.5 ka,1.6 ka,1.2 ka millennial,and 700 a,495 a,307 a and 105 a centennial scales.The 1.6 ka and 1.2 ka cycle may be related to earth orbit factors.495 a cycle may be associated with ENSO or solar activity.4.The MAP and PCA-F1scores could reconstruct the revolution of EASM specifically since 13.0 cal ka BP:during the YD period,the amount of precipitation was less;the precipitation increased from the Late Glacial Age to the Holocene,and the EASM increased obviously.The climate was wet at 11-6.5 cal ka BP and the EASM was the strong,and since3.0 cal ka BP,the precipitation decreased,and the EASM continued weak.The results show that phytolith can be used as a as reliable proxy for EASM reconstruction.