Which of the following factors may indicate a tree is at a higher risk of failing?

The factor that indicates a tree is at a higher risk of failing is minimal taper in the trunk. Taper refers to the gradual narrowing of the trunk from the base to the top. A well-tapered trunk provides better structural integrity and strength, allowing the tree to better withstand forces such as wind. When a tree exhibits minimal taper, it means that the trunk width does not sufficiently decrease from bottom to top, which can lead to a higher risk of structural failure during high winds or adverse weather conditions.

While high soil moisture, excessive leaf growth, and a healthy root system may contribute to a tree's overall health, they do not directly correlate with increased risk of failure in the same manner that trunk taper does. High soil moisture can actually support tree health if managed correctly; excessive leaf growth may indicate a healthy tree but does not imply structural weakness, and a healthy root system typically enhances stability, not diminishes it.