Modern pollen assemblages from Hamtah and Chhatru glaciers, Lahaul-Spiti, India: Implications for pollen–vegetation relationship in an alpine arid region of western Himalaya

The present study deals with the pollen analysis of 25 surface samples, 15 from the outwash plain of the Hamtah Glacier and 10 from the Chhatru glacial valley, Lahaul-Spiti, Himachal Pradesh, India. The samples were collected in a linear transect from the respective sites at an altitudinal range of ∼3200 masl to ∼4000 masl. The area is a high altitude cold desert in the western Himalaya, characterised by scrub type of vegetation. The pollen assemblages reveal an overall dominance of extra local arboreals (conifers) over the local non-arboreals. Though it is a vegetation sparse area, the alpine meadow is well represented by the presence of non-arboreal elements, such as Rosaceae, Asteraceae, Artemisia, Lamiaceae, Poaceae, Apiaceae and Chenopodiaceae/Amaranthaceae. However, predominance of Pinus has been observed along with moderate values of Abies and Picea. The overwhelming values of Pinus pollen can be attributed to its profuse production and efficient dispersal through wind currents from the temperate forests and eventual deposition around the study sites. Temperate broad-leaved taxa including Alnus, Ulmus, Betula and Corylus are present in low abundance. The consistent low frequencies of fern spores, algal and fungal elements, and absence of aquatic and marshy taxa reflect the dry climatic conditions in the region. Impact of anthropogenic activities can be observed in the form of degraded patches of tree-line and evidence of extensive grazing. Palynological data from the surface samples is not coherent with the actual vegetation around the study area due to the prolific over-representation of extra local pollen over the local herbaceous taxa. Palynological studies have been initiated in the vicinity of Hamtah and Chhatru glaciers on sub-surface sediment profiles, and this data will be helpful in developing modern analogues for understanding the past vegetational changes with respect to palaeoclimatic conditions in and around the study area.