Impacts of Ammonium Sulfate Treatment on the Foliar Chemistry of Forest Trees at the Bear Brook Watershed in Maine

Abstract

Foliar chemistry was examined in mature sugar maple (Acer saccharum Marsh), red maple (Acer rubrum L.), American beech (Fagus grandifolia Ehrh.), and red spruce (Picea rubens Sarg.) in response to chronic, watershed-level additions of ammonium sulfate [(NH4)2SO4]. Following four years of treatment, N concentrations were significantly higher in foliage from the treated watershed for all four species, with increases ranging from 6% in American beech to 33% in sugar maple. Sugar maple foliage from the treated watershed had significantly lower Ca concentrations (18%). Concentrations of K were significantly lower in beech (13%) and red spruce (9%) from the treated watershed. Foliar Mg was not different between watersheds. Aluminum concentrations were significantly higher in the foliage from the treated watershed for beech (18%), red maple (33%), and sugar maple (65%), but no differences in Al concentration occurred in current year red spruce foliage. Red spruce foliage resampled following a fifth year of treatment contained higher concentrations of N and Al and lower concentrations of Ca and Mg in the treated watershed. Despite these differences in red spruce foliar chemistry, wood production and density did not appear to be affected by the treatment.