LATE QUATERNARY VEGETATIONAL AND CLIMATIC CHANGES FROM TROPICAL PEATSIN SOUTHERN INDIA - AN EXTENDED RECORD UP TO 40,000 YEARS BP

Stable carbon isotope ratios of peats dated (by C-14) back to 40 kyr B P from the montane region (> 1800 m asl) of the Nilgiris, southern Ind ia, reflect changes in the relative proportions of C3 and C4 plant typ es, which are influenced by soil moisture (and hence monsoonal precipi tation), From prior to 40 kyr BP until 28 kyr BP, a general decline in delta(13)C values from about - 14 per mil to - 19 per mil suggests in creased dominance of C3 plants concurrent with increasingly moist cond itions, During 28-18 kyr BP there seems relatively little change with delta(13) C of - 19 to - 18 per mil, At about 16 kyr BP a sharp revers al in delta(13)C to a peak of - 14.7 per mil indicates a clear predomi nance of C4 vegetation associated with arid conditions, possibly durin g or just after the Last Glacial Maximum, A moist phase at about 9 kyr BP (the Holocene Optimum) with dominance of C3 vegetation type is obs erved, while arid conditions are re-established during 5-2 kyr BP with an overall dominance of C4 vegetation, New data do not support the oc currence of a moist phase coinciding with the Mediaeval Warm Period (a t 0.6 kyr BP) as suggested earlier, Overall, the climate and vegetatio n in the high altitude regions of the southern Indian tropics seem to have responded to past global climatic changes, and this is consistent with other evidences from India and other tropical regions.