Modern pollen-vegetation relationships and two new pollen-climate indices in the Yarlung Zangbo River basin in southern Tibetan Plateau

Abstract

This study collected 70 pollen surface samples along an east-west transection in the Yarlung Zangbo River (YLZR) basin in the southern Tibetan Plateau. Pollen assemblage and principle components analysis results show that each vegetation zone along the transection is characterized by distinctive modern pollen assemblages as follows:1) pine forest zone:Pinus pollen assemblage; 2) fir and spruce forest zone:Abies-Pinus-Picea pollen assemblage; 3) broadleaved forest/shrubland zone:Quercus-Betula-Pinus pollen assemblage; 4) alpine meadow zone:Cyperaceae-Artemisia-Compositae pollen assemblage; and 5) alpine steppe zone:Artemisia-Cyperaceae-Poaceae pollen assemblage. We use the data to define two new pollen-climate indices, (Pi, Ti), based on the ratio between major pollen taxon groups and subgroups. The indices represent the mean annual precipitation (MAP) and mean annual temperature (MAT) of the study area, and they closely track the regional west-east gradients in precipitation and temperature across the YLZR basin. We suggest that the pollen-vegetation-climate indices may be useful for future palaeoclimatic reconstructions using fossil pollen data.