Seedling growth and nutrient relationships in a New Jersey Pine Barrens soil treated with "acid rain"

Abstract

The effects of simulated acid rain solutions on growth of pitch pine (Pinusrigida Mill.) seedlings in undisturbed soil cores from the New Jersey Pine Barrens were examined. Solutions of pH 5.6, 4.0, and 3.0 (SO42−–Cl−–NO3−, 4:2:1), totaling 1.4 times annual ambient precipitation, were applied directly to soil cores from the A horizon during a 1-year period. By varying photoperiod and diurnal temperature, two growing "seasons" with an intervening dormant period were simulated. Soil chemistry, soil leachate chemistry, seedling nutrition, and seedling growth were monitored. Seedling dry weight was significantly greater at pH 3.0 than at the less acid treatments. Foliar nutrient contents indicated that growth stimulation at pH 3.0 probably resulted because of increased availability of nitrogen and input of nutrient cations from acid-induced weathering of soil minerals. There were sharp increases in Ca and Mg leaching when the pH of the irrigating solution was lowered, but solution acidity had little effect on depletion of K. Declines in nutrient leaching during the experiment indicated that weatherable cations were becoming depleted. Although Al mobility was greatly accelerated by an increase in acid inputs, Al toxicity symptoms were not observed.