ISA Certified Arborist Practice Exam

What is a significant cause of tree decline in urban settings?

1. Overcrowding of tree roots.

2. Urban pollution and soil compaction.

3. Lack of sunlight.

4. Excessive tree height.

The correct answer is: Urban pollution and soil compaction.

In urban environments, trees face numerous challenges that lead to their decline, and urban pollution combined with soil compaction represents a significant cause of this issue. Urban pollution often involves harmful substances such as chemicals from vehicles, manufacturing, and construction that can degrade air quality and soil health. These pollutants can negatively impact tree health by inhibiting photosynthesis and can lead to symptoms of stress in trees, such as stunted growth and increased vulnerability to pests and diseases. Soil compaction, on the other hand, restricts root growth and reduces the soil's ability to hold water and nutrients, which are essential for tree vitality. Compacted soil creates a barrier that makes it difficult for roots to expand and access the resources they need. When trees are unable to establish a robust root system and face the adverse effects of pollution, their overall health declines, making them less resilient in an urban setting. In contrast, while overcrowding of tree roots can be a problem, it is often a symptom of other issues rather than a primary cause of decline. Lack of sunlight and excessive tree height can also contribute to decline, but they are not as universally impactful as the combined effects of urban pollution and soil compaction encountered in densely populated areas.