Acid rain adversely effects a number of important Adirondack tree species. Reduced calcium levels in the soil due to acid rain increase the vulnerability of red spruce and hemlocks in higher elevations to damage from weather and insects.

Sugar maples, one of the commonest forest tree at middle elevations, is no longer reproducing successfully in much of the western Adirondacks. Maples reproduce through a seedling bank. The seedlings, which are highly shade-tolerant, persist for many years, growing slowly and waiting for the light from a canopy opening. The layer of preestablished seedlings, which is often quite dense, allows maple forests to regenerate rapidly after storms and harvests.

Acid rain depletes soil calcium. Most maple stands in the western Adirondacks, where the lakes are most acidified and the soils poorest in calcium, do not seem to be producing seedling banks. Their understories are dominated by young beeches. Almost no maple seedlings appear in test plots, and almost no saplings under forty years old occur in the understory. Maples require moderate amounts of soil calcium; trees on calcium-deficient soils are less vigorous, less healthy, less share-tolerant, and less capable of producing flowers and seeds. Maples in the western Adirondacks stopped reproducing just about the time acid rain reached its peak intensity and have not reproduced since.