Palaeoclimatic oscillations since last deglaciation in western Himalaya: a palynological assay

Abstract

The paper embodies the palaeovegetational and palaeoclimatic inferences deduced from the pollen analytical study of lake sediments from Khajiar, Rewalsar, Parasram Tal in Himachal Pradesh and Naukuchia Tal, Sat Tal and Tarag Tal in Kumaon Himalaya. Pollen diagrams from Himachal Pradesh (¹⁴C dated to past 3,000 yrs or so) mainly cover later part of the post-glacial climatic optimum, depicting two-fold vegetation change, i.e., oak-chirpine mixed forests to chirpine or deodar forests, reflecting the period of maximum and decreasing warmth respectively in the region. Occurrence of cerealia type pollen together with some other associated elements suggests the existence of agricultural practices in the region.

Similarly, the pollen diagrams from Kumaon Himalaya covering several lakes in Naini Tal District, depict vegetation history during Holocene. At Naukuchia Tal, it commences with chirpine woods, subsequently replaced by broad-leaved forests and then once again it reverts back to chirpine forests. Thus the changing palaeovegetation pattern in the area reflects three-fold climatic fluctuations, viz., cold to warm and again cold. Recently constructed four pollen diagrams from Sat Tal and one from Tarag Tal have revealed the dominance of chirpine-oak mixed forests around 1,000 yrs B.P. as is seen today. The vegetation pattern throughout the sequence remains more or less uniform except for the upper part of lithocolumn depicting a slight decline in the arboreal forest components around 500 yrs B.P. or so with simultaneous increase in grasses, sedges and culture pollen which reflect to the anthropogenic activity in this region also.