Soil resources of the ancient Maya at Piedras Negras, Guatemala

The ancient Maya thrived for centuries in the Petén rain forest of Guatemala. Their impressive architecture and the evidence of highly populated centers attest that the Maya farmers were capable of producing food surpluses. In the eighth to ninth centuries CE the Classic Maya civilization collapsed. The processes leading to its decline are still debated, but unsustainable agricultural practices and exhaustion of natural resources may have contributed. This paper reports on soil formation rates, soil taxonomy, phytolith analysis, and δ¹³C values of soil organic matter in a rural area near the ancient city of Piedras Negras. Our objective was to understand ancient Maya rural life by linking soil characteristics to ancient agricultural resources and anthropogenic activities. We found that these soils formed at a rate of approximately 0.09 mm yr^-1. All 15 soil profiles belonged to the order Mollisols. The soils of the back-slope locations were shallow (<25 cm) and were probably severely eroded at the time of abandonment (ninth century CE). The soils located at the valley's floor were deep, well developed, and potentially good for sustainable agriculture. Phytolith analysis indicated that in ancient times panacoid grasses were dominant in these soils and provided evidence that the forest was cleared for maize (Zea mays L.) agriculture. Stable C isotopes provided evidence that the vegetation shifted from forest (C ₃) to C₄ vegetation during the time of Maya occupation. The toe-slope soils were observed to be less enriched in ¹³C in profiles closer to Piedras Negras than in those farther away.