Controls on sulfur content in tree rings of Norway spruce and European beech at a heavily polluted site

Search for a biogeochemical archive of past sulfur pollution is motivated by the need to predict ecosystem health. Sofar, no indicator of local-scale S pollution has existed, while long-range transport of S can already be studied using polar ice records. One archive of S pollution in temperate climate zones could be annual growth rings of trees. However, S concentration patterns in tree rings of most species have been unknown because of negligible S accumulation in wood. We modified a wet chemistry procedure to increase the recovery of S from tree rings, and report time series of S concentrations in six trees from an acidified, spruce die-back affected area of Central Europe. Beech tree rings, despite 4 times lower atmospheric S inputs, exhibited twice higher S concentration in wood than spruce. The period of peak industrial S pollution of the 1980s did not result in enhanced S accumulation in tree rings of either species. Physiological processes rather than S abundance in the ecosystem regulate S storage in tree rings.