Health of Eastern North American Sugar Maple Forests and Factors Affecting Decline

Abstract Sugar maple (Acer saccharum) is a keystone species in the forests of the northeastern and midwestern United States and eastern Canada. Its sustained health is an important issue in both managed and unmanaged forests. While sugar maple generally is healthy throughout its range, decline disease of sugar maple has occurred sporadically during the past four decades; thus, it is important to understand the abiotic and biotic factors contributing to sugar maple health. Soil moisture deficiency or excess, highway deicing salts, and extreme weather events including late spring frosts, midwinter thaw/freeze cycles, glaze damage, and atmospheric deposition are the most important abiotic agents. Defoliating insects, sugar maple borer (Glycobius speciosus), Armillaria root disease, and injury from management activities represent important biotic factors. Studies of sugar maple declines over the past four decades reveal that nutrient deficiencies of magnesium, calcium, and potassium; insect defoliation; drought; and Armillaria were important predisposing, inciting, and contributing factors in sugar maple declines. Forestland managers can contribute to sustained health of sugar maple by choosing appropriate sites for its culture, monitoring stress events, and examining soil nutrition.