Late Quaternary Vegetation, Climate and Land-use History of the Horton Plains, Central Sri Lanka

Abstract

Two peat sequences from the Horton Plains, an elevated area lying at 2300 m above present sea level (a.s.l.) in central Sri Lanka, are analyzed in terms of pollen content and mineral magnetic properties. Radiocarbon dates indicate that the sequences provide an almost continuous succession of vegetation, climate and land-use history since 18,000 BP. A regional amelioration of the arid Late Pleistocene environment is indicated by the occurrence of herbaceous and summer forest communities. Xerophytic woodlands predominated at the termination of the Pleistocene, about 13,000 BP. At the very end of the Pleistocene an increase in precipitation is identified by the predominance of a montane rain forest (12,00- 11,00 BP) Changes in the Holocene vegetation are reflected in two significant rain forest expansion and diversification phases suggesting an increase in precipitation, in. the intervals 8000-7000 and 4000-3000 BP. In addition, an arid climate phase occurred from 6000 to 5000 BP and a short wet phase around 600 Bp. The first indications of human impact in the pollen diagram are dated to around 14,000 BP and may be a result of severe deforestation, forest clearance and grazing. The area may have been one of the ancestral homelands for cereal plants. A pre-farming/pastoral culture probably occurred from 14,000 to 10,000 BP, and changes in both human subsistence strategies arid the climate, with the start of agricultural land use, are reflected in the presence of pollen of Hordeum sp. and Avena sp. from 9000 to 6500 BP. Only limited agricultural activity can be identified after this time. From around 3000 BP onwards the area was abandoned, until small-scale Tritiicum cultivation took place between approximately 800 and 200 BP.