The Vegetation-Climate Relationship from the sub-surface sediment of Dokriani glacier valley, Western Himalaya

The palynological analysis of a 1.25 m deep subsurface peat profile from the subalpine meadow ( 3500 m amsl) within Dokriani glacier valley reveals the vegetation and climate since early Holocene. Since 9700 to 8200 cal yrs BP higher frequency of steppe elements viz. Artemisia, Asteraceae (Liguliflorae and Tubuliflorae) and Cheno/Ams suggest dry conditions with low soil moisture, which is more prominent between 9400-9000 cal yrs BP when the frequency of these steppe elements is highest. However some high frequency of Pinus and Abies show the pollen influx by upthermic winds from the mixed conifer forest at the then lower altitudes than present. Since 8200 till 6000 cal yrs BP the climatic amelioration with good monsoon is prominent with continuous rise of broad-leaved arboreal taxa (Quercus, Alnus, Betula, Rhododendron etc.) and conifers. Also the dominance of Polygonaceae, Cyperaceae, presence of Impatiens, Thalictrum etc. suggests good soil moisture. The profuse ground cover is also indicative of low XLF value. Also there is a continuous shift of tree-line from lower to higher altitude but with episodes of contraction and expansion of conifer-broadleaved forests. Between 6000 to 4600 cal yrs BP the high pollen frequency of Betula and Rhododendron can be linked with presence of tree-line near the sampling location suggesting the glacier snout to be at lower altitude than present. At 4600 to 3700 cal yrs BP the dominance of Quercus pollen and low frequency of steppe elements suggest moist conditions. However since 3700 till 2000 cal yrs BP the pollen frequency of Pinus increased with decline of Quercus. The prevailing conditions can be taken as dry with the reduction in south-west monsoon. Subsequently from 2000 till 1175 cal yrs BP the climate again reverted to moist with increase of Quercus pollen with relative decline in Pinus and Abies. Betula declined to its lowest values and even not recovered in some samples of this time frame. Steppe elements show small decline. Since 1175 cal yrs BP (825 AD) the pollen frequency of Quercus and Pinus again reversed with increase in later one. The impact of anthropogenic forcing in vegetation change since 2500 cal yrs BP ( 500 BC) also cannot be ruled out. The absence of Betula pollen and decline of Quercus can be considered as an effect of human forcing as these are used as fire-woods.