Late Quaternary vegetation history, climatic variability and human activity in the Central Ganga Plain, deduced by pollen proxy records from Karela Jheel, India

Abstract

Pollen analysis of a 2.6 m thick sediment profile from Karela Jheel has indicated that between 14,000 and 12,500 cal BP, open grassland with sparingly distributed trees such as Holoptelea integrifolia and Oroxylum occurred in the region under a cool and dry climate. The meager presence of aquatic elements viz., Potamogeton, Typha and fresh-water alga Botryococcus suggests the existence of the lake. Around 12,500 to 8700 cal BP, the forest groves dominated by Oroxylum together with H. integrifolia, and Madhuca indica were established, interspersed with open grasslands under a warm and humid climate in response to increased monsoon precipitation. The debut of Cerealia ∼9000 cal BP along with cropland weeds viz., Cheno/Am, Artemisia and Rumex implies the initiation of cereal-based agrarian practice. However, an abrupt decline in Oroxylum and other associated trees, except for M. indica and Acacia, which increased slightly, ∼8700 to 4800 cal BP, indicates that the forest groves became less varied in response to a warm and less humid climate, because of decreased monsoon precipitation. Between 4800 and 2000 cal BP, maximum expansion of forest groves occurred as evident by the improvement in M. indica, Acacia, H. integrifolia, etc. and invasion of more trees. The proliferation of the overall vegetation envisages the onset of a warm and more humid climate, attributed to intensification of SW monsoon. The augmentation of agricultural practice is confirmed by the steady presence of Cerealia and other cropland weeds. Since 2000 cal BP, the depletion in the arboreals suggests that the region supported open grasslands with scattered trees, depicting the deterioration of climate due to reduced monsoon precipitation.