A Late Holocene Pollen and Charcoal Record from La Selva Biological Station, Costa Rica

Pollen and charcoal analysis of a 5.9-m-long sediment profile from a swamp on an alluvial terrace on the edge of La Selva biological station, Costa Rica (10°26'23" N, 84°00'24" W, 36 m asl), documents three millennia of human and natural disturbance within a lowland tropical rain forest. The record indicates that the highly diverse rain forest that presently surrounds the Cantarrana swamp regrew following forest clearing and maize agriculture that ended only a few centuries ago. The first maize pollen appears in sediments deposited ∼1070 calendar-year BP. Older sediments below the 'maize zone' contain macroscopic charcoal, abundant microscopic charcoal, and possible pollen indicators of forest clearance, perhaps signaling local cultivation of root crops that left no pollen in the sediments. Interpretation of local archaeology indicates that La Selva reserve may have been most heavily populated during the El Bosque and La Selva regional archaeological phases from 2250–950 yr BP. However, the distribution of maize pollen in the sediments is clear evidence that the reserve was also occupied during the later La Cabaña phase (950–400 yr BP), from which few artifacts have yet surfaced. Natural forest disturbance from treefalls and stream dynamics, and hydrological shifts associated with late-Holocene climate variability, form a backdrop to the human land-use history preserved in the Cantarrana sediment profile.