Sedimentary charcoal as an indicator of late-Holocene drought in the Sierra Nevada, California, and its relevance to the future.

A Holocene record of climate, fire and vegetation regimes was reconstructed for Siesta Lake, Yosemite National Park, California, using fossil pollen and charcoal from lake sediments. These reconstructions were generated to provide a long-term perspective on drought in the Sierra Nevada. The sedimentary record is in agreement with other long-term records of climate and vegetation from the Sierra Nevada, and the records of climate and fire for the last c. 1000 years are in agreement with tree-ring and hydrological studies. This correspondence suggests that sedimentary charcoal and pollen are reliable indicators of change in climate, vegetation and fire frequency through time. The fire frequencies associated with the droughts of the 'Mediaeval Warm Period' are only half as great as those recorded during the early-Holocene insolation maximum. Model results suggest that the temperature increases associated with the insolation maximum are a good analogue for those expected with global warming. If this is the case, future droughts may be more severe than any experienced in the last several thousand years, and these data should be considered in planning for future change. [ABSTRACT FROM AUTHOR]