Airborne pollen in the Nam Co Basin and its implication for palaeoenvironmental reconstruction

While pollen is used as a palaeoenvironmental proxy, as of now there are no continuous in situ airborne pollen observations in the Tibetan Plateau. Here we present the first data of airborne pollen collected from September 2005 to August 2006 using a Burkard trap in the Nam Co Basin in central Tibet. The airborne pollen assemblage is dominated by local herbaceous Cyperaceae and Artemisia pollen, and Sabina pollen is the major arboreal taxon. Betulaceae, particularly Alnus, and Pinaceae were the dominant wind-transported pollen over long distances. Seasonal variations in the differences in amounts and taxa over time are evident. There are three clear pollen concentration peaks, in spring, summer, and early autumn, dominated by Sabina, Cyperaceae, and Artemisia, respectively. Consequently the record of pollen deposition is consistent with respective flowering periods, which are mainly a function of climate factors, especially air temperature. Backward air mass trajectory analysis suggests that non-native Alnus pollen may originate in southwestern Tibet or nearby areas. Airborne pollen data will contribute to the knowledge of modern pollen distribution and its relationship to vegetation and climate, and are useful for interpreting fossil pollen records and understanding vegetation response to climate change in the Tibetan Plateau.