As the Earth’s “Third Pole”, the Tibetan Plateau is a sensitive indicator for the global environmental change. Moreover, the Asian Summer monsoon, which nourishes about half of the world’s population, is also strongly affected and restricted by the plateau, making the region important in global climate change research worldwide and therefore have been a focus of numerous global climate change studies in recent years.
Recently, Dr. Jin-Feng Li, a member of the “Spatialtemporal Three-Pole Environment” project of CASEarth, published a paper in the journal “Earth-Science Reviews”. The work focuses on systematic analysis of the correlation mechanism between the pollen deposition patterns in the surface soil samples and the wind direction and intensity of the Asian Summer Monsoon over the Tibetan Plateau.
The research discovered:
1) the surface pollen assemblage can reflect the alpine meadows, steppe and desert vegetation which means that surface pollen data can be used to assess the deep-time vegetation;
2) most of the exotic pollen are from trees, the spatial distribution of these tree and the pollen’s relative abundance is strongly coupled with the path of the Asian Summer Monsoon and the extent to which it encroached on the Tibetan Plateau.
These results demonstrated that tree pollen deposition on the Tibetan Plateau is dominated by the Asian Summer Monsoon, i.e., the upslope movement of the modern Asian Summer Monsoon drives the spread of pollen rain from low-altitude vegetation to high-altitude areas. If a similar scenario had happened previously at different stages of the Asian Summer Monsoon evolution and the Tibetan Plateau uplift, the pollen buried in the sediments have the potential to reflect the current direction and intensity of the Asian Summer Monsoon at that time. Moreover, it would provide a simple and potentially practical proxy for the study of the evolutionary history of the Asian Summer Monsoon.
For the first time, by applying the pollen relative abundance contour, this work quantitatively illustrated the process of the tree pollen produced in the surrounding area of the plateau carried up to the Tibetan Plateau by the current of the Asian Summer Monsoon. It provided a new proxy index and research idea for evaluating the evolution of the Asian Summer Monsoon during the Tibetan Plateau uplift.
The coupling of tree pollen relative abundance contour and the isohyet on the Tibetan Plateau.
A, B and C on the figure are the tree pollen deposition centers on and surrounding the Tibetan Plateau
Li, J.-F., Xie, G., Yang, J., Ferguson, D. K., Liu, X.-D., Liu, H., & Wang, Y.-F. (2020). Asian Summer Monsoon changes the pollen flow on the Tibetan Plateau. Earth-Science Reviews, 103114. doi:10.1016/j.earscirev.2020.103114.