ISA Certified Arborist Practice Exam

How does soil pH impact tree health?

1. It determines the soil's color

2. It affects nutrient availability

3. It regulates the water flow

4. It influences tree height only

The correct answer is: It affects nutrient availability

Soil pH is a critical factor in tree health primarily because it affects nutrient availability in the soil. The pH level of the soil influences the chemical form of nutrients, which in turn determines how accessible those nutrients are to trees and other plants. Different nutrients are available to plants at specific pH ranges; for instance, many macronutrients, such as nitrogen, phosphorus, and potassium, are most available within a slightly acidic to neutral pH range (around 6.0 to 7.0). If the pH is too low (acidic) or too high (alkaline), certain nutrients may become insoluble or otherwise unavailable, potentially leading to deficiencies that can adversely affect tree growth and overall health. Understanding soil pH and its impact on tree health is vital for effective tree management, as it can influence not just growth, but also resistance to diseases, pests, and environmental stresses. This aligns with the fundamental principles of soil science and plant physiology, making it essential knowledge for arborists.