Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Heather E. EricksonConstance A. Harrington; David D. Marshall
    Date: 2009
    Source: Canadian Journal of Forest Research
    Publication Series: Scientific Journal (JRNL)
    PDF: Download Publication  (614.23 KB)


    Planting with mixtures of tree species rather than single species is often considered during reforestation because of the potential increased productivity and other benefits. We examined tree growth at the stand and individual tree scales in two experiments contrasting monocultures with a 1:1 mixture of tree species: (1) Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) with a conifer of similar shade tolerance (western white pine (Pinus monticola Dougl. ex D. Don)) and (2) Douglas-fir with a more shade-tolerant conifer (western hemlock (Tsuga heterophylla (Raf.) Sarg.)). There was no effect of mixture on growth or yield in the Douglas-fir - western white pine combination. In the Douglas-fir - western hemlock combination, yields in the mixture equaled those in Douglas-fir stands because of the enhanced performance of Douglas-fir in the mixture. For Douglas-fir, the height/diameter (h/d) ratio was significantly less in mixture, suggesting reduced competition for light when grown with western hemlock. In contrast, the h/d ratio for western hemlock was significantly greater in mixture, suggesting increased competition for light when grown with Douglas-fir. Neighborhood analyses showed that tree growth was directly related to initial size and inversely related to relative neighbor size and that the h/d ratio was positively related to relative neighbor size. In general, the size of a neighboring tree influenced growth more than species identity. Relationships between h/d ratios and growth rates suggest that growth differences between Douglas-fir and western hemlock in mixture will eventually increase.

    Publication Notes

    • You may send email to to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Erickson, Heather E.; Harrington, Constance A.; Marshall, David D. 2009. Tree growth at stand and individual scales in two dual-species mixture experiments in southern Washington State, USA. Canadian Journal of Forest Research. 39:1119-1132.


    Google Scholar


    stand yield, species mixtures, forest monocultures, competitive interactions

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page