Paleoenvironmental Change in Central California in the Late Pleistocene and Holocene: Impacts of Climate Change and Human Land Use on Vegetation and Fire Regimes

Dramatic environmental changes have occurred in the last 50,000 years in California due both to changes in climate and anthropogenic impacts. Analyses of pollen and microscopic charcoal from sediment cores from three wetland sites in central California record changes in vegetation and fire frequencies during the late Pleistocene and Holocene at different temporal resolutions. A long-term record with a basal date of ca. 50,000 cal yrs BP from a coastal wetland north of Santa Cruz shows important vegetation shifts between the Last Glacial Maximum, the glacial-interglacial transition, and the mid- to late-Holocene, as well as the introduction of a frequent fire regime in the Holocene. A 3,000-year record from a wetland near Año Nuevo State Park provides evidence of an increase in fire frequency in coastal California from the fifteenth century to the present, and vegetation changes associated with logging after Euro-American settlement. A core that spans the last ca. 700 years from an oxbow lake in the Sacramento Valley records the introduction of non-native plants into the area after European arrival. Together, these records help place the magnitude of anthropogenic impacts in the context of long-term environmental change due to regional or global climatic forcing