Published in Division of Agriculture and Natural Resources, University of California: Bulletin 1909, January 1, 1984, pages 1-13.
NOTE: At the time of publication, the author Douglas D. Piirto was not yet affiliated with Cal Poly.
A study of the causes of uprooting and stem failure in old-growth giant sequoia (Sequoia gigantea [Lindl.] Decne) indicated many factors, depending upon the type of failure (by root, stem, or earth). Advanced decay and fire scars were the most frequently associated with failure. In 21 of 33 study trees, one-third or more of the roots were judged too decayed to provide support. Twenty-seven study trees possessed basal fire scars, and 26 fell toward the scarred side. Nine Basidiomycetes, including Fomes annosus, Poria albipellucida, Poria incrassata, and Armillaria mellea, were associated with decayed wood. Carpenter ants were found in or adjacent to the failure zone of nearly half of the study trees. Physical disturbances (e.g., roads, trails, streams) were associated with 22 tree failures, but their role in initiating requires further investigating.