The whole-bole system: a conditioned dual-equation system for precise prediction of tree profiles

Demaerschalk, J. P.; Kozak, A.

doi:10.1139/x77-063

Cited by 73 publications

(51 citation statements)

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“…In the following few years, Julian P. Demaerschalk worked on the compatibility of several volume equations and some taper estimating systems for his Master's and Ph.D. theses under the direction of Dr. Smith and myself (Demaerschalk 1971(Demaerschalk , 1973. Upon graduation in 1973, Dr. Demaerschalk joined the Faculty of Forestry, and also joined our small team of taper researchers.…”

Section: The History Of Taper Research At Ubcmentioning

confidence: 97%

My last words on taper equations

Kozak¹

2004

The Forestry Chronicle

210

384

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A brief review of the nearly half century of research related to taper equations in the Faculty of Forestry at the University of British Columbia is presented. Two new variable-exponent taper models, the 2001 and 2002 models, are introduced and compared to Kozak's 1988 and models. This comparison, based on 38 species groups consisting of 53 603 trees, demonstrated that the 2002 model is consistently the best overall model of the four, and the 2001 model is the simplest in form and the best for estimating merchantable height. The results of this study also indicate that several fit statistics and lack-of-fit statistics should be used to create indices for ranking taper models for practical applications, instead of only a few.

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Section: The History Of Taper Research At Ubcmentioning

confidence: 97%

My last words on taper equations

Kozak¹

2004

The Forestry Chronicle

210

384

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“…They may provide reasonable estimates in the mid-portion of the bole, but are usually less accurate for estimating the profile in the butt or upper stem segments (Demaerschalk and Kozak, 1977;Max and Burkhart, 1976;Newnham, 1992).…”

Section: Stem Taper Selected Functionsmentioning

confidence: 99%

Un modèle pour l’estimation du volume commercialisable du pin sylvestre dans les principales régions de montagne d’Espagne

2009

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Abstract• Accurate estimation of stem volume makes it possible to estimate the monetary value of one of the many commodities and services that forests provide to society, i.e. timber.• In the present study a compatible volume system for Scots pine in the major mountain ranges of Spain (the Pyrenees, Southern Iberian Range, Northern Iberian Range, Soria and Burgos Mountains, Central Range and Galician Mountains) was developed with data from 2 682 destructively sampled trees. Several well-known taper functions were evaluated. A second-order continuous-time autoregressive error structure was used to correct the inherent autocorrelation in the hierarchical data, allowing the model to be applied to irregularly spaced and unbalanced data.• The compatible segmented model of Fang et al. (2000) best described the experimental data. It is therefore recommended for estimating diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for the six mountain ranges analyzed.• The non-linear extra sum of squares method indicated differences in mountain range-specific taper functions. A different taper function should therefore be used for each mountain range in Spain.Mots-clés : équation de forme / modèle segmenté / équation compatible / pin sylvestre Résumé -Un modèle pour l'estimation du volume commercialisable du pin sylvestre dans les principales régions de montagne d'Espagne.• L'estimation précise du volume des tiges permet d'estimer la valeur du bois qui est un des nombreux produits et services que la forêt apporte à la société.• Dans cette étude, nous avons développé un modèle compatible de volume du pin sylvestre avec les mesures obtenues pour 2 682 arbres abattus dans les principales zones de montagne en Espagne, les Pyrénées, le sud et le nord de l'Ibérie, les montagnes de Soria et Burgos, le centre et les montagnes de Galice. Nous avons évalué plusieurs équations de profil de tiges bien connues. Pour corriger les autocorrélations inhérentes aux données hiérarchiques, nous avons utilisé un modèle d'erreur autoregressif à l'ordre 2 en temps continu, ce qui permet au modèle d'être appliqué à des données irrégulièrement espacées dans le temps et non équilibrées.• Le modèle segmenté compatible de Fang et al. (2000) décrit le mieux les données expérimentales. Il est donc recommandé pour estimer le diamètre à une hauteur donnée, la hauteur à un diamètre donné, le volume commercial et le volume total pour les six zones montagneuses étudiées.• La méthode des moindres carrés généralisés non linéaires indique des différences entre équations de profils de tiges des différentes zones montagneuses. Il faut donc utiliser une équation de profil de tige par zone de montagne en Espagne.

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“…The inflection point is where the stem profile changes from neiloid to paraboloid, and its relative height is thought to be constant within a given species, regardless of tree size (Demaerschalk and Kozak 1977). Parameters A and B, which deal with the conversion from outside to inside bark diameter, are assumed to be constant within a given species, and can be estimated with any appropriate data set (e.g., Garber and Maguire 2003).…”

Section: Model Simplificationmentioning

confidence: 99%

A simple stem taper model with mixed effects for boreal black spruce

et al. 2009

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We simplified Kozak's taper model by setting the inflection point at 1.3 m (dbh) without losing accuracy and precision. The simplification was required to facilitate the estimation of the covariance parameters when using a mixed-effects method. This method was necessary to take into account the correlation among multiple diameter measurements on an individual stem. The simple stem taper model was fitted to an extended data set collected across the province of Quebec, Canada. Comparison of the predicted stem taper and the derived stem volume with those obtained using existing models showed a comparable predictive power for the simple model. Including a prediction of the tree random effects based on supplementary diameter measurements of the bole improves the predictive ability of the model around the extra diameter observation. This model offers welcome simplicity as a means of predicting tree taper at coarse resolution for planning tree harvesting.

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The whole-bole system: a conditioned dual-equation system for precise prediction of tree profiles

Cited by 73 publications

References 0 publications

My last words on taper equations

My last words on taper equations

Un modèle pour l’estimation du volume commercialisable du pin sylvestre dans les principales régions de montagne d’Espagne

A simple stem taper model with mixed effects for boreal black spruce

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