Holocene pollen record from Lake Gahai, NE Tibetan Plateau and its implications for quantitative reconstruction of regional precipitation

Located in the northwestern edge of the modern Asian summer monsoon (ASM), the northeastern Tibetan Plateau (NETP) is sensitive to changes of the ASM climate. However, variations of climate and vegetation during the Holocene remain unclear in this marginal region of the monsoon climate. Here we present a Holocene highresolution pollen record from Lake Gahai in the NETP since 11.4 (+/- 0.3) ka BP to reconstruct regional vegetation history. A quantitative reconstruction of precipitation is also tried using fossil pollen assemblages. Results suggested that before 10.2 (+/- 0.4) ka BP in the early Holocene, the vegetation cover was low and the climate was arid. A relatively wet climate indicated by high A/C ratio values occurred between 10.2 (+/- 0.4) and 7.4 (+/- 0.2) ka BP. After 7.4 (+/- 0.2) ka BP, the A/C ratio decreased, indicating that the climate was getting drier. The overall environment of the basin has become similar to modern conditions since 5.4 (+/- 0.1) ka BP. The reconstructed precipitation is not comparable with the tree-ring-based reconstruction from the Delingha region, although the reconstruction processes passed significance tests statistically. In addition to abundant surface pollen data and gradually improved quantitative reconstruction techniques, other factors such as the environmental settings and vegetation dynamics also affect the reliability of the pollen-based quantitative reconstruction of regional precipitation. Therefore, the applicability of pollen data for quantitative precipitation reconstruction in arid regions should be assessed and the results should be treated cautiously.