Form factor functions for nine commercial tree species in Bhutan

Tenzin, Jigme; Wangchuk, Tenzin; Hasenauer, Hubert

doi:10.1093/forestry/cpw044

Cited by 15 publications

(20 citation statements)

References 24 publications

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“…The stem diameter of a tree decreases gradually from the ground to the top. The rate of decrease in diameter along the stem is called the stem taper (Tenzin et al 2017;West 2004), and depends on various characteristics, including genetics, silviculture, site, and climatic characteristics (Ikonen et al 2006;Karlsson 2000;Nigh and Smith 2012;Pukkala et al 2019;Schneider et al 2018). Knowledge of the stem taper is indispensable for estimating the total or merchantable volume of trees (Tenzin et al 2017;Wijenayake et al 2019).…”

Section: Introductionmentioning

confidence: 99%

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

2021

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The form-factor for the stem surface area is directly proportional to the square root of the form-factor for the stem volume, i.e., the square root law of the form-factor. Although the square root law addresses the stems of coniferous trees, the nature of the proportional coefficient of the law has not been discussed. In this study, we demonstrated that the coefficient indicates the stem taper; therefore, it is named “Taper Index based on Form-Factor (TIFF).” We also examined the relationship between the form-factor for the culm surface area and the form-factor for the apparent culm volume of 570 culms across three bamboo species (Phyllostachys pubescens Mazel ex Houz., P. bambusoides Sieb. et Zucc., and P. nigra var. henonis). The square root law held true for all three bamboo species. The species-specific TIFF was determined to be 0.873 for P. pubescens, 0.897 for P. bambusoides, and 0.901 for P. nigra. This result implied that P. pubescens had a more tapering culm form compared to the other two species, while culm taper was similar between P. bambusoides and P. nigra. Our findings align with empirical observations of the culm taper of the bamboo species. Intra-species variation in TIFF was considerably small, allowing us to evaluate the species-specific culm taper from a small number of samples. Therefore, we conclude that TIFF provides a simple and useful method for quantifying species-specific culm or stem taper, and facilitates the estimation of merchantable or total volume.

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Section: Introductionmentioning

confidence: 99%

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

2021

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“…The artificial form factor (f1.3) of i-th tree was obtained dividing the actual volume (method of Huber) by the volume of a perfect cylinder, which was obtained and based on the total height and transverse section (1.30 from the ground) (Eq.1) (TENZIN et al, 2017;PACHECO et al, 2017). In general, after the factor (f1.3) calculated for each tree, an average value can be used to obtain estimates for the volume of the standing tree.…”

Section: Artificial Form Factor (F13)mentioning

confidence: 99%

“…In general, after the factor (f1.3) calculated for each tree, an average value can be used to obtain estimates for the volume of the standing tree. Thus the volume of the i-th tree (m 3 ) can be calculated using the formula in Eq.2, where: vi = volume of the i-th tree (m 3 ), diameter 1.30m from the ground; gi = sectional area of the i-th tree, measured 1.30 from the ground (m 2 ), hi = height of i-th tree; (m), and f = form factor (ADEKUNLE et al, 2013;TENZIN et al, 2017). FLORESTA, Curitiba, PR, v. 50, n. 3, p. 1669-1678 Successful mathematical models used in the prediction of the artificial form factor f1,3 of other species in planted stands (see DRESCHER et al, 2001;DRESCHER et al, 2010;BOTH et al, 2011;CUNHA NETO et al, 2016) were chosen for modeling employing classical linear regression using ordinary least squares (OLS).…”

Section: Artificial Form Factor (F13)mentioning

confidence: 99%

“…Parametric approaches such as linear regression have been the main focus of many modeling studies of the form factor of trees in forests of unequal ages and of the same age (e.g., DRESCHER et al, 2001;DRESCHER et al, 2010;BOTH et al, 2011;ADEKUNLE et al, 2013;CUNHA NETO et al, 2016, TENZIN et al, 2017. However, nonparametric approaches, such as artificial neural networks, have been shown to be appropriate in modeling forest attributes (e.g., DIAMANTOPOULOU;MILIOS, 2010;MARTINS et al, 2016, SANQUETTA et al, 2018.…”

Section: Introductionmentioning

confidence: 99%

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k-NEAREST NEIGHBOR AND LINEAR REGRESSION IN THE PREDICTION OF THE ARTIFICIAL FORM FACTOR

Souza

Nievola

Corte

et al. 2020

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Resumo k-vizinhos mais próximos e regressão linear na predição do fator de forma artificial. A proposta deste estudo foi testar se a abordagem não-paramétrica, conhecida como k-Nearest-Neighbor (k-NN), poderia melhorar as estimativas do fator de forma artificial (f1,3) individual de árvores do híbrido Eucalyptus urophylla x Eucalyptus grandis, em comparação ao método de Mínimos Quadrados Ordinário. Foram selecionadas e derrubadas 149 árvores-amostras e medidos ao longo do fuste os diâmetros a 10% (d0,1), 30% (d0,3), 50% (d0,5) e 70% (d0,7) da altura do fuste comercial e, posteriormente, a cada 2m. Modelos matemáticos reconhecidos na literatura para predição do fator de forma foram ajustados para comparação. O hiperparâmetro k de ajuste ótimo para o estimador k-NN foi obtido através de repetidas validações cruzadas. Os dados de treinamento do modelo de regressão k-NN foram idênticos aos utilizados no ajuste dos modelos de regressão linear. A maior parte dos modelos de regressão linear múltipla apresentou problemas de colinearidade ou multicolinearidade. O uso da covariável (0.3. 0.7)/ 1.3 2 e k = 15 possibilitou a construção de modelos k-NN com melhor capacidade de generalização. O potencial do estimador k-NN para predizer o fator de forma artificial e, por conseguinte, obter estimativas menos viesadas dos volumes individuais de árvores foi admitido e, considerado superior ao uso da regressão linear e fatores de forma médios. A abordagem k-NN pode ser considerada mais genérica para predizer o fator de forma de árvores, e seu uso pode ser aconselhado quando modelos de regressão linear clássicos, ou outros métodos mais simples, não mostrarem bons resultados. Palavras-chave: Eucalyptus, aprendizado de máquina, vizinho mais próximo, regressão linear, fator de forma 0,7

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“…Por lo tanto, el error levemente menor encontrado en el modelo 2 y la necesidad de contar con dos variables en lugar de tres requeridas por el modelo 3, permitiría inclinar la decisión por el primero. Por otra parte, del modelo 3 se podría cuestionar el uso de un factor de forma generalizado en cada clon como una variable fija cuando está demostrado que este parámetro generalmente disminuye con el aumento del DAP y la altura total tal como fuera observado por Pollanschütz (1965) y recientemente por Tenzin et al (2016). Clutter et al (1983) han dado diversas razones por las que se prefieren los modelos que utilizan solo el diámetro y la altura ya que las mismas explican a menudo gran parte de la variación de volumen causada realmente por las diferencias de forma.…”

Section: Discusión Y Conclusionesunclassified

Ajuste de modelos de volumen de fuste para Populus x canadensis ‘Conti 12’ y ‘Guardi’ en plantaciones irrigadas de Mendoza, Argentina

2019

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Despite the extensive literature on model fitting to estimate volume in different tree species and regions of Argentina, the references related to volume equations for Populus spp. in irrigated plantations in the Province of Mendoza are scarce. This information is essential for silvicultural management. The objectives of this study were: 1) to calculate and compare the artificial form factors for Populus x canadensis 'Conti 12' and 'Guardi' clones growing in irrigated plantations in Uco Valley, Mendoza, 2) to fit and compare different equations of stem volume with bark for these two clones and 3) to evaluate the possibility of using a single function to estimate this parameter in both clones. Seven models previously used on Populus in Argentina were fitted to estimate the total stem volume per tree. The form factors for 'Conti 12' and 'Guardi' were different between them (0.44 and 0.38, respectively). For both, 'Conti 12' and 'Guardi', the adjustment of the seven models allowed estimating the total stem volume with bark with a very high and similar degree of precision, although in both situations two models (Schumacher-Hall and a variant of the standard function with constant form factor) highlighted over the rest. The statistics of self-validation, homoscedasticity and parsimony criteria allow favoring the decision for the Schumacher-Hall model adjusted individually for each clone and not as a general expression.

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Form factor functions for nine commercial tree species in Bhutan

Cited by 15 publications

References 24 publications

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

k-NEAREST NEIGHBOR AND LINEAR REGRESSION IN THE PREDICTION OF THE ARTIFICIAL FORM FACTOR

Ajuste de modelos de volumen de fuste para Populus x canadensis ‘Conti 12’ y ‘Guardi’ en plantaciones irrigadas de Mendoza, Argentina

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Form factor functions for nine commercial tree species in Bhutan

Cited by 15 publications

References 24 publications

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

k-NEAREST NEIGHBOR AND LINEAR REGRESSION IN THE PREDICTION OF THE ARTIFICIAL FORM FACTOR

Ajuste de modelos de volumen de fuste para Populus x canadensis &#8216;Conti 12&#8217; y &#8216;Guardi&#8217; en plantaciones irrigadas de Mendoza, Argentina

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Ajuste de modelos de volumen de fuste para Populus x canadensis ‘Conti 12’ y ‘Guardi’ en plantaciones irrigadas de Mendoza, Argentina