Vegetation vis á vis climate change around Bhogdoi swamp in lower Brahmaputra flood plain of Assam, Northeast India since Late Holocene

Abstract

Pollen records from 1.8 m deep sedimentary profile cored from Bhogdoi swamp, Kamrup District, lower Brahmaputra flood plain of Assam, Northeast India have revealed enrichment of tropical mixed deciduous forest elements including Shorea robusta, Syzygium cumini, Dillenia pentagyna and Acacia catechu indicating warm and humid climatic regime during 3,795–2,530 years BP. Subsequently during 2,530–680 years BP relative increment in proliferation of tropical mixed deciduous elements namely Lagerstroemia parviflora, Lannea coromandelica, Terminalia bellirica, Sapotaceae and Emblica officinalis occurred resulting into final settlement of tropical mixed deciduous forest under increased warm and humid climatic regime attributable to active Southwest Monsoon. However, from 680 years BP onward gradual deterioration of mixed deciduous forest occurred as evidenced by sudden decline in Sal and its associates under warm and relatively drier climate. Drastic increment in Melastoma, Ziziphus and Areca implying forest clearance at this phase. The occurrence of degraded pollen–spore along with adequate fungal remains especially Xylaria, Diplodia, Nigrospora and Microthyriaceous fruiting body is suggestive of aerobic microbial digenesis of rich organic debris during sedimentation.