Abstract
Pollen and charcoal analysis of a 5.6-m sediment core from Lago de las Morrenas (9°29′N, 83°29′W; 3480 m) provides evidence of postglacial vegetation and fire history in the highlands of the Cordillera de Talamanca, Costa Rica. The site is presently surrounded by treeless páramo vegetation and apparently has been so since deglaciation about 10,000 yr B.P. Pollen spectra suggest no pronounced changes in vegetation since ice retreat. Fires set by people or lightning have burned the páramo repeatedly, with fire activity probably highest during the late Holocene, but these fires have not carved páramo from forest. Pollen percentages for Gramineae and other páramo taxa decline upward, whereas percentages for certain subalpine, lower montane, and lowland forest taxa increase slightly; these changes may reflect the impact of prehistoric human activity or slight upslope migrations of forest taxa owing to climatic warming. There is no clear evidence of higher timberlines during the mid-Holocene.
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