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°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 (δ¹³C) measurements of the subfossil leaves constrain the interpretation of the inferred changes in the operation of the global carbon cycle. The δ¹³C 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.