Terrestrial soil profiles provide local, fine-scale resolution evidence of vegetation and fire history as well as evidence for human modification. In each of the study areas we open test units to collect samples for phytolith, charcoal and soil organic matter analysis, and for the analysis of carbon isotopes and soil geochemistry. We use the column sampling method to collect samples at 5 cm intervals from the soil profiles.

Because of the lack of nearby lakes in many ‘terra firme’ settings, such as the geoglyphs region, these soil profiles often provide the only evidence of human disturbance outside of the archaeological sites. When lakes are present, however, the higher temporal resolution of lake sediments, with their more regional signature, can be used to complement the local data from the test units.