Laser Photoacoustic Detection of CO(2) in Old Disc Tree-Rings

A homemade CO(2)–laser photoacoustic spectrometer has been used for monitoring CO(2) in gas samples extracted under vacuum from the wood of old spruce disc tree-rings for a ∼60 year series. The experimental results show that (1) the CO(2) concentration exhibits annual trends correlated with an increase in atmospheric CO(2) in a number of cases; (2) at the time when the annual CO(2) trend changes from positive to negative, the annual tree-ring stable carbon isotope ratios (δ(13)C) of CO(2) change as well; (3) the disc tree-ring widths are observed to decrease in most cases where the annual CO(2) increased; (4) simultaneously with the annual CO(2) variation, annual H(2)O distribution was detected in gas samples of the wood tree-rings of one spruce disc. The observed patterns of the annual CO(2) distribution in the disc tree-rings are assumed to be the evidence of the impact of the atmospheric CO(2) increase. In other words, a change in the concentration gradient between the stem and the atmospheric CO(2) may lead to a gradual CO(2) accumulation in the stem because of a decrease in the diffusion rate and to a change in the tree parameters.