INTERPRETING δ13C ENRICHMENT OF SOM FROM MAIZE AGRICULTURE ON ANCIENT MAYA SITES

Enrichment of δ¹³C values for SOM from maize agriculture is non-linear and appears to reach a plateau or falloff within a period of two decades. Consequently, it is possible that our interpretations of ancient Maya economies based on the stable carbon isotope analysis of SOM underestimate local maize production. Models of C4 maize ecosystems overestimate the δ¹³C enrichment of SOM from maize agriculture because they are based on δ¹³C values on maize kernels rather than from roots or other parts of the plant. After more than a century of maize cultivation, δ¹³C values of SOM increase only ~2‰.