Late Holocene vegetation and climate change in Loktak Lake region, Manipur, based on pollen and chemical evidence

Abstract

The pollen and elemental analyses from a 73 cm deep sediment profile from Loktak Lake region, Manipur have provided insight into the changing vegetation and climatic scenario in the region during the Late Holocene. The investigation has revealed that between 1650 and 600 yr B.P., open vegetation comprising largely grasses and heathland taxa Asteraceae, Chenopodiaceae/Amaranthaceae, etc. with sprinkle of trees viz., Holoptelea, Symplocos, Acacia, etc. occurred in the region adjoining to the lake. The good profusion of ferns, fungal and algal remains as well as presence of aquatics implies that a humid climate prevailed in the region. The low C/N ratio also corroborates such climatic condition. The retrieval of Cerealia and other cultural pollen taxa denotes some sort of agricultural practice in the vicinity of the lake. From 600 yr B.P. to Present the expansion of open vegetation and a contemporary reduction of trees infer the inception of a less humid climate probably owing to reduction in monsoon precipitation. This is also evidenced by a sharp decline in ferns, fungal and aquatic elements. However, the agricultural practice continued with same pace, as before since the culture pollen taxa do not show any distinct alteration.