There are lesions on the foliage, nutrient loss from the leaves, a reduced resistance to the environment, pathogens and insects, an accelerated erosion of the leaf wax, a reduced rate of decomposition of the leaf litter, the inhibition of the formation of the terminal buds, an increased mortality of seedlings and heavy metal accumulation. There is also a reduction in tree growth, the dying of useful microorganisms that are symbiotic with tree roots and the inhibition of the nitrification of ammonium compounds. Scientists have seen the symptoms of trees under acid rain stress. Trees have physical damage to the roots and foliage, a reduced canopy cover, crown dieback, a reduced growth rate and finally whole tree death. Much of the problems are due to the leaching of aluminum from aluminum silicates when the pH of soil water has reached 4.0.
Aluminum damages the root hairs and reduces the uptake of phosphorus and other nutrients.
The tree later dies from starvation and a reduced resistance. Foliar leaching is also possible. Ammonia and nitrogen may land on the leaf, either wet or dry, and pass through the semi-permeable membrane on the leaf surface. It will then be incorporated into the leaf cells. Acid rain also has the effect of reducing the rates of decomposition on the forest floor.