B.C. Ministry of Forests Forest Science Program
			Abstract of SIL345

		Growth Intercept Method for Silviculture Surveys
		Author or Ministry Contact: Patrick Martin
		Branch: Forest Practices Branch (formerly Silviculture Practices Branch)
		Subject: Growth and Yield
		Series: Silviculture
		Other details:  Published 1995. Hardcopy is available

Abstract

The growth intercept method predicts site index from height and age measurements taken on carefully selected sample trees. This method of calculating site index is being calibrated for many tree species in B.C. As of August 1995, the method was available for interior lodgepole pine, interior spruce, and coastal western hemlock. In 1996, growth intercept tables will be available for coastal Douglas-fir, interior Douglas-fir, and interior western hemlock.

These procedures replace those described in the memo Using the preliminary growth intercept method to estimate site index in young lodgepole pine stands.^l

The old preliminary method required the surveyor to identify the first five annual branch whorls immediately above breast height and measure this amount of height growth. The new method, described in this document, requires the surveyor to measure total tree height and age at breast height.

Compared to the old method, the new method has the following benefits:

• Can be applied to younger stands;
• Is suitable for species with and without regular annual branch
  whorls;
• Produces a more accurate site index estimate under many
  circumstances; and
• Integrates better with existing and proposed silviculture survey
  methods.

¹ Memo dated October 14, 1994, from Henry Benskin, Director, Silviculture Branch, to all regional
silviculture officers and district silviculture resource officers.

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Updated October 08, 2004

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