C-13 IN TREE-RINGS ALONG AN AIR-POLLUTION GRADIENT IN THE KARELIAN ISTHMUS, NORTHWEST RUSSIA AND SOUTHEAST FINLAND

We measured delta(13)C in the annual rings (years:1954-1992) of Scots pine (Pinus sylvestris L.) trees in nine sample plots of an air pollut ion monitoring network in northwest Russia and southeast Finland. Tree s in plots closer to the pollution sources tended to have less negativ e delta(13)C values (>C-13 in their wood) than those in more distant, northern plots. Moreover, between about 1960 and 1992, there was a ten dency for delta(13)C to become increasingly negative (i.e., <C-13) in five of the plots. In four plots delta(13)C values fluctuated about th eir mean without any time trend. The results suggest that the forests nearest the pollution sources were mon severely stressed during the fi rst 3 decades than final 1 of the sample period, probably because of t he heavy, chronic S and N emissions originating from the St. Petersbur g region and northeast Estonia, and probably also Central Europe.