The variable growth intercept modelling technique is applied to three species of interior spruce in the Sub-Boreal Spruce and Engelmann Spruce-Subalpine Fir biogeoclimatic zones -- Engelmann (Picea engelmannii Parry), white (P. glauca [Moench] Voss), and their cross. The variable growth intercept model allows foresters to estimate spruce site index from the first 1-30 years of height growth above breast height of a stand. Good results were obtained from the analysis of the model development data. However, testing indicated that the model may be biased (it underestimates site index). Nevertheless, interior spruce site index can be estimated with the model, but the model should be evaluated more thoroughly.
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Updated October 24, 2008