Pollen analysis of sediment core NQ-1

A total of six samples from core NQ-1 are collected to identify pollen assemblage (Table S3). These samples are pre-treated to remove carbonates, silicates, and humic acid with HCL (30%) and HF (40%). Pollen counts are performed on glycerin jelly slides using a Leica DM4000 B microscope at 400× magnification (Leica Microsystems) at Guangxi Normal University, China. The relative proportion of pollen species is calculated based on total terrestrial pollen (not all palynomorphs), while the species percentage of spores and algae was based on the sum of all palynomorphs (Hao et al., 2021). The pollen was identified following the procedures of Tang et al. (2018).