Certified Arborist Practice Exam

What is the cumulative impact of stress leading to a plant's decline over time known as?

1. Senescence

2. Decay

3. Nutrient deficiency

4. Mortality spiral

The correct answer is: Mortality spiral

The cumulative impact of stress leading to a plant's decline over time is recognized as a 'mortality spiral.' This term describes a situation where a plant experiences multiple stressors, such as environmental changes, soil degradation, pest infestations, or diseases, which progressively weaken its health. As the plant's condition deteriorates, its ability to recover diminishes, making it increasingly vulnerable to further stress. This cyclical pattern often accelerates the decline of the plant, creating a downward spiral toward death. In contrast, senescence refers to the natural aging process of a plant, where it gradually loses function, but doesn’t necessarily imply a cumulative impact from stresses over time. Decay typically involves the physical breakdown of plant material, often as a result of disease or rot, without directly addressing the overarching stress factors. Nutrient deficiency relates specifically to the lack of essential nutrients in the soil affecting plant health, but again does not encapsulate the broader cumulative impacts of various stressors on a plant's vitality.