A Holocene CO2 record from the stomatal index of subfossil Salix herbacea L. leaves from northern Sweden

A stomatal-based method of palaeo-CO2 estimation has been applied to a temporally detailed sequence of leaves from a high-latitude lake (68 degrees N) in northern Sweden spanning the last 9000 years. The resulting atmospheric CO2 reconstruction documents the onset of a gradual increase c. 5000 years before present indicating that the carbon cycle has not been in steady state over this time. Stable carbon isotope (delta(13)C) measurements of the subfossil leaves constrain the interpretation of the inferred changes in the operation of the global carbon cycle. The delta(13)C data reveal no marked or systematic shifts towards more negative values indicating that the CO2 addition to the atmosphere 5000-1000 yr BP may have been predominantly of oceanic origin.