Sensing plant community and climate change by charcoal-carbon isotope analysis

Abstract

AbstractMass spectrometric carbon isotope (δ13C) analyses of charcoal-carbon found in lake sediments provide evidence of paleoclimate and paleovegetation independent of pollen. By chemically separating the microscopic charcoal-carbon, which originates from upland fires, from total carbon in lake, ocean, or ice cores, changes in C3/C4 biomass of upland plant communities can be measured, wet or dry climates identified, and the evolution of specific plant assemblages traced. In the North American Midwest, δ13C values of lake sediment charcoal-carbon from Lake Mendota, Wisconsin, U.S.A., document two shifts from C3 (forests) to C4 (prairie grasses) plants since deglaciation: an abrupt change at about 8.5 ka (8 500 years BP) and a longer duration change between 6 and 3 ka. A pine-savannah is interpreted for the earlier date while oak-savannah dominated the landscape between 6 and 3 ka. C4 biomass, which was almost non-existent in the region before 8.5 ka, increased to more than 50% between 6 and 3 ka. Spruce-t...