Two new height models for volume estimation of lodgepole pine stands

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Abstract
To reduce the cost and increase the efficiency of obtaining individual tree height information required for sample plot volume estimation, two general height–diameter (H/D) regression models were developed using two-stage regression analysis and data from 96 lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) sample plots. The derived models were examined using an independent data set of 28 plots. In addition to diameter at breast height (D), these models also included two easily measurable stand parameters as independent variables: quadratic mean diameter (Dq) and the height of a tree with diameter Dq (Hq). With a practical method to estimate Hq (from up to three heights measured) and using these two new H/D models in conjunction with available regional standard volume equations (V = f (D,H)), the stand volume estimates, on the average, were 0.003% higher (SD 4.1%) for the first model and 1.081% lower (SD 4.6%) for the second model than those obtained using traditional H/D curves for each plot based on 30 or more height measurements. The new models are therefore recommended for use in height estimation of lodgepole pine trees within the range of conditions of the data. This approach may be applied to other species and regions.