Representation of vegetation and climate by modern pollen assemblages on the south-eastern Tibetan Plateau

Abstract

Modern pollen distribution and how it relates to vegetation and climate along elevational gradients is crucial information when reconstructing past vegetation and climate from fossil pollen assemblages. In this study, sixty-five samples of moss polsters were collected from an elevation range of 1069–5056 m a.s.l. on the south-eastern Tibetan Plateau (TP) and the relationships between their pollen assemblages and vertical variations in vegetation and climate are investigated. Our results indicate that variations in the pollen assemblages along the elevational gradient reflect the vertical distribution of vegetation. Arboreal pollen grains (predominantly Pinus, Quercus-evergreen, and Betula) can be transported by the wind to high-elevation areas, but percentages of Quercus-evergreen pollen > 10% likely indicate a local source. Thus, interpreting local vegetation from low arboreal pollen percentages can be challenging for stratigraphic pollen assemblages in the south-eastern TP. A redundancy analysis and a boosted regression tree analysis both find that mean temperature of the coldest month (Mt_co) explains more of the pollen assemblage variance and the arboreal pollen to non-arboreal pollen (AP/NAP) ratio, accounting for 7.07% and 43.11% respectively. Therefore, Mt_co is the most important climatic factor influencing pollen distribution on the south-eastern TP.