Tree roots best absorb nutrients in a soil pH of 6.5 to 7.5. When the pH is above 7.5, micronutrients such as zinc, iron and manganese become less soluble and therefore less available for tree uptake.
Trees in alkaline soils with pH from 7.5 to 10 may develop micronutrient deficiencies that diminish chlorophyll production. Symptoms include dieback, browning of leaves and even eventual death.
Sweetgum and red maple are especially susceptible to micronutrient deficiencies on alkaline soils.