Why are sugar maple trees affected by high aluminum and low calcium in soil?

Sugar maple populations in the northeastern United States and eastern Canada are declining due to the detrimental effects of acid rain on soil chemistry.

The process affects these trees through two primary mechanisms:

• Nutrient Depletion: Calcium is a vital nutrient necessary for healthy plant growth. Acid deposition leaches these essential base cations from the soil, depriving trees of the resources they need to thrive.12
• Aluminum Toxicity: As soil becomes more acidic, aluminum that is normally bound to soil particles and rocks is released into a toxic, dissolved form. This high concentration of dissolved aluminum interferes with the ability of tree roots to take up necessary nutrients.12

Combined, these factors weaken the trees, making them more susceptible to additional environmental stressors such as drought, pests, and extreme cold.12