Today, the Ohio River valley is still dotted by enormous coal-burning power plants with stacks as high as 1000 feet. These tall stacks allow the sulfurous pollution to travel 1000 miles or more, where it forms acid rain across the Adirondack mountains of New York, and across northern New England and southern Canada. In Vermont, the rain has a pH of 3.8 to 4.0. But meanwhile, acid rain had been falling on northern New York and New England and on southern Canada for about 20 years. What Hub Vogelmann has been able to show by studying Camel's Hump for 30 years is that acid rain doesn't just affect the trees - it affects the soil and thus the entire ecosystem.
Soil contains a large amount of aluminum, but it occurs in the form of aluminum silicates.
In that form, aluminum is not available to the roots of plants. But acid rain dissolves the silicates, releasing the aluminum and making it available to plants. When plants get aluminum into their roots and their vascular system, the roots clog, which prevents the plant from taking up adequate nutrients and water. The trees are weakened, and may then fall prey to extreme cold, or to insects or pathogens that a healthy tree can withstand. Acid rain not only releases aluminum into the soil.