LATE QUATERNARY VEGETATIONAL CHANGE IN THE CENTRAL PERUVIAN ANDES

New fossil pollen records from the central Peruvian Andes at elevations above 4000 m including pollen-concentration data and additional radiocarbon dates, provide information on late Quaternary vegetation change for the region. A pollen assemblage typical of superpuna plus low pollen concentrations, and % organics in the late glacial section of Laguna Tuctua indicate a cold/dry climate, but strong evidence for a late glacial climate reversal, i.e., the Younger Dryas, is not presently confirmed. An abrupt increase in Urticales pollen as Compositae and Polylepis-Acaena type pollen decline signals the beginning of the Holocene. Subsequent increases in Urticales and Plantago rigida type pollen point to increased moisture as well as higher temperatures from about 11,000 to 7000 yr B.P. A possible correlation exists between the rapid expansion of puna and closed continuous forest and the rise in importance of camelids in the early Holocene. In the mid-Holocene Plantago rigida cushion bogs and continuous montane forest elements decline, suggesting a drier climate. Grasses and Cheno-Ams then increase, reaching maxima about 4000 yr B.P. Pastoralism and agriculture are thought to have developed at this time, according to ethnobotanical studies from this area, and pollen evidence seems to support these findings. Between 3000 and 2000 yr B.P. pollen percentages of Poaceae, Plantago rigida type, and other local taxa decline as glacial activity was renewed in the higher mountains. Zea mays is present by 2000 yr B.P., and pollen of weeds and secondary successional plants associated with increasing agricultural disturbance are evident.