ISA Certified Arborist Practice Exam

Which factors can contribute to tree crown reduction?

1. High soil moisture

2. Excessive tree weight

3. Prolonged sunlight exposure

4. Frequent pruning

The correct answer is: Excessive tree weight

Tree crown reduction can be influenced by various factors, and excessive tree weight is one of the key contributors. When a tree has excessive weight, often due to a high density of leaves or fruits, it may not be able to support its own structure effectively. This overload can lead to stress on the branches and ultimately cause the tree to naturally reduce its crown size as a survival mechanism. In some cases, the tree may initiate this reduction to decrease the weight it must support, thereby lessening the risk of branch failure or structural collapse. Additionally, the tree may adapt to this stress by shedding leaves or branches to redistribute resources and maintain overall health. High soil moisture, prolonged sunlight exposure, and frequent pruning do not inherently lead to crown reduction in the same manner. While high soil moisture might support growth, prolonged sunlight exposure can enhance leaf production, and regular pruning may encourage healthy growth — all under the right conditions. In contrast, excessive weight directly links to structural stress and the necessity for the tree to adjust its crown accordingly.