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A Mathematical Approach to Polymorphic Site Index Curves for Grand Fir

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Polymorphic site index curves may be derived for Abies grandis by fitting to stem analysis data the sigmoid function: H = a exp(--b / Ac). This procedure uses the tree as a phytometer to estimate site index. To arrive at a site quality measure closely corresponding to periodic stand increment, the estimation procedure compensates for the effect of site factors that affect the tree only during the seedling and sapling stages of development. Site index is here defined by the annual height increment on a tree 55 feet tall, but expressed as tree height at an index of 50 years. The number of annual rings in 1.5-inch radius from the pith at breast height is used to select the appropriate set of height/age curves from the polymorphic series. Such curves constructed from stem analyses must be applied to a uniform number of the tallest trees per acre at all ages. This number is tentatively set at the rate of 25 trees per acre.

Document Type: Journal Article

Affiliations: Mensurationist, Intermountain For. and Rge. Expt. Sta., Forest Service, U.S. Dept. Agric., Moscow, Idaho.

Publication date: 1963-06-01

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  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Average time from submission to first decision: 62.5 days*
    June 1, 2016 to Feb. 28, 2017

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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