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    Author(s): Connie Harrington; Kevin Ford; Brad St. Clair
    Date: 2016
    Source: Tree Planters' Notes. 59(2): 76-85.
    Publication Series: Scientific Journal (JRNL)
    Station: Pacific Northwest Research Station
    PDF: Download Publication  (8.0 MB)


    Phenology is the study of the timing of recurring biological events. For foresters, the most commonly observed phenological events are budburst, flowering, and leaf fall, but other harder to observe events, such as diameter-growth initiation, are also important. Most events that occur in the spring are influenced by past exposure to cool (chilling) temperatures and also to warm (forcing) temperatures. For trees in the Pacific Northwest, chilling temperatures generally promote earlier growth initiation, but species differ in their sensitivity to chilling and forcing and to whether some minimum amount of chilling is required for certain events, such as budburst, to occur at all. The initiation of diameter growth for the studied species does not require chilling and may begin 6 to 8 weeks before height growth. The timing of height growth may affect the pattern of diameter growth early in the season. The timing of reproductive events for conifers varies by species and can occur well before vegetative growth begins. This paper was presented at the annual meeting of the Western Forest and Conservation Nursery Association (Eugene, OR, October 26–27, 2015).

    Publication Notes

    • Visit PNW's Publication Request Page to request a hard copy of this publication.
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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Harrington, Constance A.; Ford, Kevin R.; St. Clair, Bradley. 2016. Phenology of Pacific Northwest tree species. Tree Planters' Notes. 59(2): 76-85.

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