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Recent studies suggest that anthropogenic nitrogen and sulfur deposition may be an important control on tree carbon assimilation and stomatal conductance. Temperate deciduous forests in the eastern United States have been subjected to high levels of acid deposition in the past century, but few studies have addressed the impacts of deposition on forest carbon and water cycles in these systems. We investigated the influence of climate and atmospheric deposition on tree productivity and water-use efficiency at the Fernow Experimental Forest in West Virginia. Tree core samples from four deciduous species were collected in Fernow Watershed 3, which has received ammonium sulfate treatments three times annually since 1989, and Watershed 7, an adjacent control catchment. Tree cores were analyzed for annual growth increment as well as stable carbon isotope ratios. We found that tree growth response to …