PARENT SESSION
Poster Session #22: Paleoecology.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Landuse signatures by prehistoric human populations in an old growth rainforest.

Malone, Christopher¹, Sanford, Robert¹, ¹

ABSTRACT- Prehistoric human uses of neotropical rainforest in Costa Rica have left telling changes that still remain in forest soils. The primary objective of this study is to quantify these changes by looking at the distribution of soil charcoal and levels of soil phosphorus (P) in relation to areas of concentrated human activity. Soil cores, two meters in depth, were taken every 30 m along topographical transects radiating away from known archaeological sites under old growth forest at La Selva Biological Station, Costa Rica. Soil charcoal was removed by sieving and sorting at 10 cm intervals. The phosphorus levels at 0-10 cm, 50-60 cm and 90-100 cm were determined using the Hedley fractionation procedure. 22% of the cores contained charcoal in samples deeper than 1 m. One site contained 0.80g/m² and 3.95g/m² of charcoal(0-100 cm and 100-200cm respectively), while another had 405.06g/m² and 26.98g/m². Hedley fractions indicate that biological P at the surface changes from 12%(68gP/g soil) of total P to 23%(39gP/g soil) of total P at depth. In contrast at another site, biological P changes from 38%(226gP/g soil) at 0-10 cm to 28%(59gP/g soil) of total P at 90-10 cm. These data are important in explaining the results of prehistoric human effects on neotropical rainforest.

KEY WORDS: soil charcoal, soil phosphorus, neotropical rainforest, human activity