Studies in the late quaternary vegetational history in Himachal Pradesh- 2. Rewalsar lake

Abstract

The paper embodies the results of pollen analytical investigations carried out at Rewalsar lake in Himachal Pradesh. The whole pollen sequence has been divided into several stages (a-e) as to facilitate the description of the pollen diagram. The Rewalsar lake is nearly 800 cm deep and is C-14 dated at two levels, i.e., 170 and 290 cm to 520 ± 55 and 1410 ± 60 years B.P. respectively. The date for bottom portion of the profile can be extrapolated to about 4000 years B.P. and thus whole sequence belongs to the "Post-glacial period ".

The vegetational stages as marked in the pollen diagrams to show the vegetational changes. The ‘Stage a’ the lowermost part of the lake basin is comprised of the forest in which oak appears to be the most dominant element followed by Pinus and Corylus with an undergrowth of grasses together with Artemisia and Cheno-Amarant. The succeeding ‘Stage b’ is almost in accordance with the preceding ‘Stage a’ except for a little rise in Quercus. ‘Stage c’ is differentiated from the preceding stages by the consistent rise in the values of Corylus and corresponding fall in the values of Quercus. The high altitude elements such as Pinus wallichiana, Abies, Picea and Cedrus have either gained or emerged during this stage. The ground flora except for minor fluctuations remains the same. ‘Stage d’ is marked by the tremendous decline in oaks and Corylus corresponding with a sudden rise in the values of Pinus roxburghii from the beginning of this stage. ‘Stage e’ is characterized by tremendous fall of Quercus giving pace to the grasslands comprising Gramineae Cyperaceae, Compositae, Artemisia, Cheno-Amarant type and Cerealia type.