ISA Certified Arborist Practice Exam 2026 - Free ISA Arborist Practice Questions and Study Guide

The opposite of acidic on the pH scale in trees is alkaline. The pH scale ranges from 0 to 14, where values below 7 indicate acidity, 7 is neutral, and values above 7 indicate alkalinity. Therefore, when discussing soil pH in the context of trees, soil that is alkaline has a higher pH (greater than 7), which means it has a lower concentration of hydrogen ions compared to acidic soil. This distinction is important for tree health and growth, as different tree species have specific pH preferences that can influence nutrient availability and overall vitality. Understanding the pH scale is essential for arborists when assessing soil conditions and making management decisions for various tree species.