A 14 000 year sedimentary charcoal record of fire from the northern Sierra Nevada, Lake Tahoe Basin, California, USA

This research examines how the controls of fire episode frequency in the northern Sierra Nevada have varied at different temporal scales through the Holocene. A 5.5 m long sediment core was collected from Lily Pond, a ~2.5 ha lake in the General Creek Watershed on the west shore of Lake Tahoe in the northern Sierra Nevada in California, USA. Dendrochronology was used to reconstruct the recent history of fire, and high-resolution charcoal analysis was used to reconstruct fire episodes for the last 14 000 cal. yr BP. Fire episode frequency was low during the Lateglacial period but increased through the middle Holocene to a maximum frequency around 6500 cal. yr BP. During the late Holocene fire episode frequency generally declined except for noted peaks around 3000 cal. yr BP and 1000—800 cal. yr BP. These variations track major climatic and vegetation changes driven by millennial-timescale variation in the seasonal cycle of insolation and regional decadal- and centennial-scale variation in effective moisture in the mid and late Holocene in the Sierra Nevada. Fire episode frequency during the Holocene in the Lake Tahoe Basin varied in response to decadal-, centennial-and millennial-scale climatic variability. Current fire episode frequency on the west shore of Lake Tahoe is at one of its lowest points in at least the last 14 000 years. Given the strong relationship between climate and fire episode frequency, warming due to increased levels of greenhouse gases in the atmosphere may increase fire episode frequency to levels experienced during the `Mediaeval Warm Period' or the early-Holocene summer insolation maximum as periods of drought intensify.