ISA Certified Arborist Practice Exam 2024 - Free ISA Arborist Practice Questions and Study Guide

Co-dominant stems in tree morphology refer to when two stems of equal size arise from a union. This feature can have significant implications for tree health and structure as the two stems can lead to included bark, which is a weak point where the two stems grow together. This can result in structural weaknesses, making the tree more susceptible to failure, particularly in high winds or storms. Therefore, recognizing and managing co-dominant stems is crucial for maintaining the structural integrity of the tree and ensuring its long-term health and safety. Options A, B, and C are incorrect because co-dominant stems do not indicate old age in the tree, imply disease resistance, or signify a strong root system. These factors are determined by various other characteristics of the tree and are not directly related to the presence of co-dominant stems in tree morphology.