VERIFICATION OF AGRICULTURAL PRACTICES THROUGH REMOTE SENSING AND STABLE ISOTOPE ANALYSES OF CROPLANDS IN THE YUCATAN, MEXICO

This study seeks to document a history of land use change through the use of remotely sensed information, ground-truthed by stable isotope analysis of soils. Using soils collected from agricultural fields in the Southern Yucatan Peninsular Region of Mexico, the history of land use practices has been characterized. In these areas, substantial amounts of tropical dry forests have been cut down and cleared for agriculture since the late 1960's. The removal of old growth deciduous forests along with a conversion to croplands is recorded in the 13C compositions of the soils, as well as remotely sensed observations over the sites. Typical cultivation practices consist of relatively small (1 to 2 ha) plots being cleared and used to cultivated Zea mays for periods from two to three years, followed by ten to twenty years of a fallow period, before being cultivated again. Recently, as transporting the crops has become easier, a greater portion of farmers have shifted to cultivating the more profitable jalapeno chile. Soil cores from thirty-six locations are compared at multiple depths and analyzed for organic carbon and total nitrogen contents, as well as δ13C and δ15N; the results document the change from forest to corn to chile agriculture and the 15N compositions record the introduction of Haber process fertilizers.