Macroscopic Charcoal as Evidence of Long-Term Fire History in the Cuatro Cienegas Valley, Mexico

In this study, I present a high-resolution sedimentary charcoal record of fire for a freshwater marsh in the Cuatro Ciénegas Basin of Mexico. The basin lies within the grasslands of the Chihuahuan Desert ecoregion where opportunities for fire history studies are exceptionally rare. In this arid environment, fire-scarred trees are restricted to montane forests, and depositional environments conducive to the preservation of charcoal are uncommon. The charcoal record comes from a 12.3 m sediment core that extends to the late Pleistocene and includes various sediment types. Sediment typed proved to be a major influence on charcoal concentration. During dry times, burning of the sediments themselves caused exceptionally high charcoal concentrations for peat intervals of the core. Charcoal was sparse during the late glacial period, but increased dramatically in the Holocene. An age reversal in the sediments between 1092 cm and 930 cm complicated the record for the early Holocene, but the middle Holocene was characterized by abundant charcoal and by what appears to be a drier climate around the study site. The late Holocene contained some of the largest charcoal peaks in the core, and includes elevated charcoal production in the Medieval Warm Period and a marked decrease at the onset of the Little Ice Age. The most recent few centuries are missing from the sediment record, but included are key intervals of the Holocene and Late Pleistocene. The abundance of charcoal demonstrates that fires have been an integral part of the Cuatro Ciénegas ecosystem and must be better understood to properly manage this sanctuary of biodiversity in the future.