Phytotoxicity of American beech leaf leachate to sugar maple seedlings in a greenhouse experiment

In an effort to reexamine the factors that affect codominance of American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marsh.), a greenhouse experiment was conducted to test the potential phytotoxic effects of American beech leaf leachate on sugar maple seedlings. We utilized an experimental protocol that addressed phytotoxic, nutrient, and pH effects by watering seedlings with seven treatment solutions: simulated throughfall water, average and dilute concentrations of beech leachate, average and dilute concentrations of maple leachate, and average and dilute concentrations of nutrient solutions. Sugar maple leachate had no effect on sugar maple seedling development, chemistry, or physiology. However, sugar maple seedlings exposed to average levels of beech leachate had significantly lower leaf area, fewer nodes, lower biomass, higher carbon assimilation rates, and higher stomatal conductance than seedlings exposed to the control solution. Results suggest that secondary compounds in beech leaf leachate are suppressing sugar maple seedling development and that field experiments are needed to explore the potential allelopathic relationship between these species.