A HOLOCENE VEGETATION HISTORY FROM LOWLAND GUATEMALA

A 5.45-m core from Lake Peten-Irza, lowland Guatemala, contains a near -complete record of Holocene sedimentation. The age-depth relationship for the core is based on AMS C-14 dating of terrestrial wood fragment s and provides a reliable chronology in this karst region where hard-w ater lake error has typically confounded sediment geochronology. In th e basal part of the sequence, pollen of the Moraceae-Urticaceae group dominate, indicating the presence of widespread tropical forest during the early Holocene (c. 8600-5600 yr BP). Relative abundance of pollen of high forest taxa declined beginning as early as 5600 yr BP, indica ting climatic drying or perhaps initial land clearance. Deforestation by prehistoric Mayan inhabitants is documented clearly in the pollen r ecord beginning about 2000 pr BP (106 cal BC-122 cal Ao, 95.4%, 2 sigm as) by the appearance of disturbance taxa (e.g. Ambrosia and Poaceae) and presence of Zea. Forest regrowth occurred following the Classic Ma ya collapse, c. AD 900, as reflected by a relative increase in Moracea e-Urticaceae pollen.