Magnesium deficiency symptoms associated with sugar maple dieback in a Lower Laurentians site in southeastern Quebec

Observations made in 1987 on sugar maple (Acersaccharum Marsh.) dieback in the deciduous forest of the Lower Laurentians, northwest of Quebec City, revealed the occurrence of magnesium deficiency in various sites. Visual foliar symptoms observed on sugar maple in a severely declining stand growing on well-drained, stony, loamy-sand soil of granitic origin are briefly described and illustrated. Magnesium concentrations in the foliage of both trees and regeneration in early August averaged 0.06% (range 0.03–0.09%). Other tree or plant species present also exhibited conspicuous magnesium deficiency symptoms. The occurrence of magnesium deficiency in this and other sites of the deciduous forest in the Lower Laurentians contrasts with the general absence of this deficiency in a previously studied large section of forest in the Quebec Appalachians, where soils are derived from other rock formations.