Modern Pollen Assemblages of Surface Samples from Tropical Deciduous Forest of Assam, Northeast India: A Window to Palaeoclimatic Interpretation

Palynological assessment of 20 surface samples from the Panchratna reserve forest of Goalpara District, western Assam has been carried out to explore the relationship between modern pollen assemblages and contemporary vegetation patterns. Seven spider web samples have also been examined in order to conceive air pollen-spore and its relation to soil/moss pollen data. The surface samples have depicted the occurrence of mixed pollen assemblage comprising Angiosperms, Gymnosperms and Pteridophytes among which non-arboreals (terrestrial herbs and marshy/aquatic taxa) dominate over arboreals (trees and shrubs). The comparison between pollen spectra and vegetation reflects site to site variation in pollen assemblage in relation to heterogeneity of the forest. The occurrence of highland plants is suggestive of long distance transportation of pollen from higher elevation. The affluence of both monolete and trilete fern spores indicate humid climatic condition. Pollen frequencies of surface samples somehow portray the extant floral distribution in and around the reserve forest which is well evidenced from our palynological data where relative frequency of the assemblage includes local arboreals at the average values of 33.91%, 22.88% and 11.33% at centre, margin and open-land area of the forest respectively. Thus, the surface samples from near proximity of the woods dominate in the arboreal pollen frequencies which are quite relevant to extant floral composition. The representation of fungal elements belongs to Deuteromycetes and Ascomycetes (grass pathogen) as evidenced by degraded pollen and spores which are suggestive of biological degradation in sediments. Therefore, there is a need to precisely observe the behavioural pattern of modern pollen deposition which could be helpful in deciphering past climate and vegetation in and around the pristine floodplain ecosystem of Northeast India which is at the verge of deterioration.