PARENT SESSION
Tuesday, August 8, 5:00-6:30 pm
Poster Session 10 - Genetics, evolution, and paleoecology
Exhibit Hall, Ballroom Level, Cook Convention Center
A 20,000 year paleoecological history of a Peruvian montane forest.
Valencia, Bryan1, Bush, Mark1, Hillyer , Rachel1, 1 Florida Institute of Technology, Melbourne, Fl
ABSTRACT- We present the first multiproxy paleoecological record from within the elevation of cloud forest in Peru (3050 m elevation). The record, from Lake Pacucha (13° 36′ 30′′S; 73°19′ 50′′W) spans the last 20,000 years and provides the most detailed view yet available for a site close to tree-line. The transition from full glacial to Holocene conditions is evident as a change from grassland, through Polylepis woodland to mixed evergreen montane forest. The deglaciational period appears to have been one of relatively high moisture availability. About 11,000 years ago, increased temperatures and falling precipitation combine to cause a drop in lake level. Deposits of gypsum between c. 10,000 and 8000 cal. yr BP indicate a lowstand event. Laminations in these sediments suggest strong seasonality, i.e. dry season drawdowns of lake level. A wetter oscillation is evident between c. 8500 and 6500 cal. yr BP, prior to a further dry episode at c. 6300 cal. yr BP. Prior records from the central Andes have suggested either an early Holocene dry event, c. 10,500 cal. yr BP at sites at 7-9 oS, or a mid-Holocene dry event, c. 9000-4200 cal. yr BP at sites at 16-18 oS. While the overall trajectory of lowered lake level between c. 11,000 and 5,500 cal. yr BP matches the reduction in January (wet season) insolation as suggested in these other studies, Pacucha offers the first record from the Andes that so clearly shows two cycles of low lake level, suggesting two processes.
Key words: montane forest, paleoecology, central Andes