Peter Douglas

There is evidence from lake and cave records in Mexico suggesting that the Terminal Classic decline of the Maya civilization coincided with a series of major multi-decadal droughts.  However there are few paleoclimate records from the Peten region of Guatemala, which was the political and population center of the Classic Maya civilization.  I am applying leaf-wax hydrogen and carbon isotope measurements to lake sediment cores from Mexico and Guatemala to help resolve the impact of drought on the Classic Maya across this region.  I am also exploring the potential for compound specific radiocarbon measurements of leaf waxes in lake sediment cores to constrain long-term changes in soil organic carbon reservoirs in the Maya lowlands.  I am working to created records of the mean soil residence time of leaf waxes for the past 3000 years in lake sediment cores across the Maya lowlands, and to examine how climatic and anthropogenic drivers affected soil storage of leaf waxes through this interval.I have been analyzing leaf-wax isotope values in lake sediments, soils and plant tissue from a large aridity gradient across southeastern Mexico, Guatemala and Honduras to better constrain leaf-wax isotopic variability in the tropics.  This research highlights the important influence that variability in aridity and vegetation can have on leaf-wax hydrogen isotopes. In addition, I have been analyzing the compound specific radiocarbon content of leaf waxes from lake sediments from this study area.  These measurements indicate that the mean age of sedimentary leaf wax lipids is significantly older than the age of sediment deposition, suggesting that a large component of leaf waxes are stored for long periods of time in soil organic carbon reservoirs.  I am exploring the environmental factors controlling soil storage of leaf waxes and the implications of this storage for leaf-wax stable isotope paleoclimate studies.