Role for heavy metals in forest decline indicated by phytochelatin measurements

FOREST decline in the United States and Europe has been documented for a number of tree species(1,2) and atmospheric pollutants from industrial sources, such as acids or oxidants, are thought to be partly responsible(1-4). Heavy metals hare also been implicated because their deposition pattern is correlated with forest decline(5-11), but so far there has been no direct evidence for a physiological link between tree damage and exposure to metals, Here we use the concentrations of phytochelatins, which are intracellular metal-binding peptides that act as specific indicators of metal stress(12,13), to show that metals are indeed likely to be a contributing factor in the decline of forests in the northeastern United States, Phytochelatin concentrations in red spruce, a species in decline, are higher than in balsam fir, a species which is not, Concentrations increase with altitude, as does forest decline, and they also increase across the region in forest stands that show increasing levels of tree damage.