Rapid response of tree cellulose radiocarbon content to changes in atmospheric ¹⁴;CO₂ concentration

Abstract

A detailed radial profile for the 14C concentration in tree stem cellulose, covering growth rings for the years 1962—1964, was obtained for a Sitka spruce of the US Pacific Coast using accelerator mass spectrometry. The tree cellulose 14C closely follows atmospheric 14CO₂ concentrations, responding to changes with an apparent delay of 5 to 6 weeks. The delay in response is mostly due to the addition of between 13% and 28% of biospheric CO₂ to the canopy-air CO₂ used by the tree for stem cellulose. Delayed incorporation and the use of stored photosynthate of the previous fall appear less important.