ISA Certified Arborist Practice Exam

Discoloration and leaf drop are indeed common symptoms of tree stress. When trees experience stress due to factors such as drought, nutrient deficiency, pest infestations, or environmental changes, they often exhibit visual signs of this turmoil. Discoloration can manifest as yellowing or browning of leaves, indicating that the tree is not metabolizing nutrients effectively or is suffering from water stress. Leaf drop is a defense mechanism employed by trees to conserve resources and minimize damage during periods of stress. By shedding their leaves, trees reduce water loss and focus their energy on survival rather than maintenance.

In contrast, vibrant foliage typically indicates a tree in good health and receiving adequate nutrients and water, which does not correlate with stress. Overproduction of flowers could suggest that a tree is healthy and thriving under optimal conditions. Thicker bark formation usually occurs as a tree matures and does not serve as a direct indicator of stress, typically being a sign of adaptation to an environment rather than a response to stress. Thus, discoloration and leaf drop effectively represent the signs of adversity a tree may face when stressed.