TRANS-GLACIAL VEGETATION HISTORY OF LAKE TITICACA (BOLIVIA/PERU)

Lake Titicaca (16° to 17.50° S, 68.5° to 70° W; 3810m) is the highest great lake in the world, and its sediments provide an opportunity to investigate long-term climate change across glacial cycles. Analysis of fossil pollen and spores of a 136-m core from the main basin and a 119-m core from the sub-basin Huinaimarka revealed significant changes in community composition from glacial to interglacial cycles. Increases in the fossil pollen concentrations of Polylepis, Chenopodiaceae and Poaceae signal not only temperature increases, but precipitation shifts within the Altiplano. Strong similiarities are evident between the pollen concentration record from Titicaca and the methane record from Vostok. The pollen data reveal distinct differences between the last four interglacials. Community composition changes are unique between and within the Holocene, MIS 5e, MIS 7, and MIS 9. MIS 5e stands out as being a more extreme event than any of the other interglacials.

High-resolution sampling revealed shifts in pollen concentration and charcoal on a sub-millenial time scale. Fire is demonstrated to be a natural component of high Andean interglacial ecosystems. During glacial episodes, low productivity leads to insufficient biomass to carry a fire. Pollen concentration in these high Andean lakes appears to be strongly correlated with the productivity of the regional vegetation. Sub-millennial variations in pollen concentration between 30-70 ka BP are seemingly co-incident with the Dansgaard-Oeschger cycles identified in the North Atlantic, suggesting an interhemispheric teleconnection.