Modern vegetational distribution and pollen dispersal study within Gangotri glacier valley, Garhwal Himalaya

Modern pollen-vegetation relationship has been analyzed in respect to vegetational distribution and pollen dispersal from sub-alpine and alpine ecological regimes within the higher reaches of the Gangotri glacier valley. The results in general cope with the local ecological conditions of the sites within the valley. Above the tree line limits, the pollen frequency of arboreal taxa is found lower than those of non-arboreal taxa. In contrast the pine-birch forest area at Chirbasa represented the frequency of arboreal pollen (AP) more than that of non-arboreal pollen (NAP) due to over representation of Pinus wallichiana (conifer). Pollen grains of extra-local arboreal elements, mostly conifers have also been recorded here with fair amount of temperate broad-leaved arboreal taxa viz. Quercus, Alnus, Corylus, Carpinus, Ulmus, Juglans etc. that have been transported by the upthermic winds from their growing limits at lower altitudes to the study sites at higher altitudes. Non-arboreal taxa viz. marshy/aquatic, steppe and of other herbaceaous taxa, represents the existing ecological regimes of their respective sites within the valley. Differential pollen preservation has been observed between the moss cushion and sediment samples from the same site that may be due to the direct exposure of moss cushions to air, thus showing more concentration of wind pollinated pollen-spores as compared to surface sediments.