Canadian national taper models

Abstract

Work was done to gather stem taper data for most forest tree species across Canada. They were used for producing taper models to be applied for the purposes of the national forest inventory and for regional purposes when regional taper models are not available. The models are based on squared DBH and on measured or predicted tree height. A taper equation based on the dimensional analysis approach was adopted to fit Canadian national taper models using the collected data. The model parameters were estimated using a mixed model for taking into account variance heterogeneity and withintree autocorrelation. In spite of the different protocols for data collection, the accuracy of the proposed stem taper models is similar to that found in previous studies. Consequently, the models seem suitable for pre-harvest estimation of sawlog volume nationally or regionally.

Evaluation of Whole Tree Growth Increment Derived from Tree-Ring Series for Use in Assessments of Changes in Forest Productivity across Various Spatial Scales

“…(1) National DBH (1.1) Volume is estimated from DBH only, using a national equation [26] (2) National DBH and HT (2.1) Volume is estimated from DBH and uncorrected height (HTr), using a national equation. [26]; heights as in B1.1 or B1.2 (2.2) Volume is estimated from DBH and corrected height (HTc) using a national volume equation (3) Regional DBH and HT (3.1) Volume is estimated from DBH and uncorrected height (HTr), using a regional equation.…”

“…where d is the diameter at different cross-section heights (h), indices i, j, k, and m respectively refer to province, plot, tree, and cross section, β 0 , β 1 , and β 2 are fixed-effect parameters, and δ i , δ ij , and δ ijk are random effects associated with the province, plot, and tree, respectively [26]. We also tested two methods that use both DBH and H as predictors.…”

“…We also tested two methods that use both DBH and H as predictors. The first was also a national level taper equation (VNdh) [26]:…”

“…where d is the diameter at different cross-section heights (h), indices i, j, k, and m respectively refer to province, plot, tree, and cross section, β 2 is a fixed-effect parameter, and δ i , δ ij , and δ ijk , are random effects associated with the province, plot, and tree, respectively [26] (Table S2). The second was a different taper equation (VRdh) [27], for which regional parameter estimates were generally available [28][29][30]:…”

“…[26]; heights as in B1.1 or B1.2 (2.2) Volume is estimated from DBH and corrected height (HTc) using a national volume equation (3) Regional DBH and HT (3.1) Volume is estimated from DBH and uncorrected height (HTr), using a regional equation.…”