Late-Holocene maize cultivation, fire, and forest change at Lake Ayauchi, Amazonian Ecuador

Abstract

A high-resolution paleoecological record provides a 2690 year-long fossil pollen and charcoal history from Lake Ayauchi, Ecuador, in lowland Amazonia. The record begins with a landscape that is already partially deforested and in which maize is being grown. Dated charcoal fragments from local soils coincide with fire events and peaks of land clearance seen in the lake sediment record. After c. AD 550 grass pollen becomes less abundant, as a broad array of forest types show small increases in abundance. Between c. AD 750 and 1280, Zea mays pollen was at its most abundant. Although maize cultivation continued until the AD 1700s, forest pollen abundance showed a significant increase at c. AD 1260. Another transition at c. AD 1420, which saw a transition from dominance by early successional taxa and an increase in mid-successional elements, suggests the onset of reduced human activity at the site. Fossil maize is found in a lower proportion of samples, disappearing altogether for a century in the late 1700s. Forest taxa increase in abundance and charcoal disappears from the record at c. AD 1790. These data suggest a complex social history prior to and following European arrival with phases of forest clearing and episodes of apparent regrowth at c. AD 500, 950, and 1260. Increased forest pollen after c. AD 1260 and a reduction in maize pollen abundance suggests some abandonment, with a second, relatively late, depopulation following European Conquest (c. AD 1790). Evidence is not found supporting reforestation associated with European arrival.