Acid rain can have terrible effects on a forest. The acid takes away important minerals from the leaves and the soil.
Minerals are like vitamins for trees and plants. Without them, trees and plants cannot grow properly. They lose their leaves and become very weak. They are no longer strong enough to fight against illnesses and frost. They become very ill and can even die.
Some soils are alkaline, when acid rain falls on them the acid becomes neutral. Plants and trees living on these soils are not in any big danger..