Surface pollen distribution in alpine zone of the higher Himalaya: a case study from the Kalla glacier valley, India

In order to understand the relationship between modern pollen spectra and vegetation, we analysed 20 surface sediment samples collected from the alpine zone of Kalla Bank glacier valley, Dhauliganga Basin, India covering an elevational stretch of c. 3600 to 5000 m asl and vegetation zones like the alpine scrub, alpine meadow and alpine barren. This study also provides insights into the vertical pollen transport along the elevational gradient of the glacier valley. Numerical analyses such as cluster analysis (CA), discriminant analysis (DA) and detrended correspondence analysis (DCA) are used to explore and discuss the modern pollen deposition patterns in the alpine settings. Despite the inconsistencies observed between modern vegetation and surface palynoassemblages, a good agreement is noticed between CA and DA classifications and DCA ordination results which reveal signature of upslope wind transport. High percentages of pine, cedar, alder and birch pollen grains in the above tree-line surface pollen assemblages are indicative of their upslope wind transport from a lower elevation. The inconsistencies may be attributed to the differential pollen representation between species, differential flowering and pollination of herbaceous taxa. The present study suggests altitude and monsoonal winds might be the two most influential factors that attributed changes in the surface palynoassemblages of the alpine vegetation in the Kalla Bank glacier (Kunti-Banar) valley. Therefore, while interpreting the fossil pollen spectra from any high altitude mountainous zone, long-distance pollen transport should always be taken into account, especially for anemophilous plant taxa.