Soil properties and stable carbon isotope analysis of landscape features in the Petexbatún region of Guatemala

Soil properties and stable carbon isotope ratios contained in the soil organic matter (SOM) were used to investigate the change in vegetative history of land cleared anciently for maize (Zea mays L.) agriculture in the Petexbatun region of Guatemala. Maize and other C4 plants associated with land clearance leave a carbon isotopic signature in the SOM different from the C3 plants of native forest vegetation. Soil profiles were collected from various landscape features around the Classic Maya site of Aguateca: control locations (areas likely not used in ancient agriculture), defensible locations (areas near defensive walls), rejolladas (natural karst depressions), upland locations (well-drained soils atop the Aguateca escarpment), and bajos (seasonal and perennial wetlands). The chemical and physical properties of the profiles were examined and the soils were taxonomically classified to the great group level. The changes in d13C with soil depth were determined and compared statistically. The 13C enrichment of the SOM in bajo and rejollada profiles were similar and were significantly (p < 0.05) greater than the control, defensible, and upland soils. This isotopic signature of sustained C4 vegetation was likely associated with forest clearance and ancient Maya agriculture. Both the bajo and rejollada landscape features appear to have been valuable agricultural resources for ancient Maya. © 2009 Wiley Periodicals, Inc.