Tree Declines: Four Concepts of Causality    (View PDF)

W.A. Sinclair and G.W. Hudler

Abstract: The term decline refers to premature progressive loss of vigor and health, not necessarily to any specific disease or disorder. Any case of decline can be explained on one of four bases. 1. A tree may decline primarily as the result of chronic irritation by a single agent. 2. A tree may decline because of damage by secondary agents after an injurious event such as defoliation or major wounding. The same agents would not cause decline in an uninjured tree, and the injury alone would not cause decline. 3. Chronic irritation by one or more agents may diminish the tolerance or resistance of a tree to another agent that then incites decline. Various factors including those that predisposed the tree and incited decline may then contribute to further decline. 4. Trees of similar age growing in groups tend to display group behaviour including premature senescence (synchronous cohort senescence) in response to stress.

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https://doi.org/10.48044/jauf.1988.009