A total of 31 taper functions from 3 different groups of models (single, segmented and variable-form taper functions) were fitted to diameter-height data from 203 Pinus pinaster trees sampled across even-aged stands in Galicia (northwestern Spain). Most of the taper functions analyzed showed problems of multicollinearity as indicated by the condition number. A second-order autoregressive CAR(2) error process was incorporated into the models to minimize the effect of autocorrelation inherent in the longitudinal data used, and to provide valid tests of significance for model parameter estimates. In general, variable-form taper functions provided the most accurate predictions. The flexibility and predictive performance of the variable-form model developed by Kozak (For Chron 80(4):507–515, 2004) indicated its usefulness for estimating diameter at a specific height, merchantable volume, and total volume of Maritime pine in the study area.

Stem taper functions for maritime pine (Pinus pinaster Ait.) in Galicia (Northwestern Spain)

Un modele hauteur-diametre pour Pinus radiata D. Don en Galice (nord-ouest de l'Espagne). Vingt-six modeles prenant en compte le rapport hauteur-diametre en fonction des variables de masse (diametre maximal, diametre dominant, hauteur dominante, hauteur moyenne arithmetique, âge, nombre d'arbres par hectare, qualite du site, etc.), ont ete evalues par rapport aux donnees relatives a 9686 arbres, grâce a des procedures de regression lineaire et non lineaire. La precision des modeles a ensuite ete evaluee par validation croisee. Les donnees correspondent a deux inventaires realises sur 182 parcelles permanentes de Pinus radiata D. Don reparties dans toute la Galice, au nord-ouest de l'Espagne. La comparaison des modeles a ete effectuee suite a l'etude du coeflicient de determination, du biais, de l'ecart quadratique moyen et du critere d'information d'Akaike. Un F-Test a ete utilise pour comparer les valeurs prevues et observees. Les meilleurs resultats ont ete obtenus avec les modeles comprenant une variable independante en lien avec la hauteur de la masse (moyenne ou hauteur dominante), bien que cela implique un gros effort d'echantillonnage pour Son application. Le modele de Tome a permis d'obtenir les meilleures evaluations de hauteur.

/pdf/a-height-diameter-model-for-pinus-radiata-d-don-in-galicia-2wxfjyfoaq.pdf

A height-diameter model for Pinus radiata D. Don in Galicia (Northwest Spain)

Dynamic growth model for Scots pine (Pinus sylvestris L.) plantations in Galicia (north-western Spain)

A stand basal area growth system for radiata pine (Pinus radiata D. Don) plantations in Galicia (Northwestern Spain) was developed from data corresponding to 247 plots measured between one and five times. Six dynamic equations were considered for analysis and both numerical and graphical methods were used to compare alternative models. The equation that best described the data was a dynamic equation derived from the Korf growth function by the generalized algebraic difference approach (GADA) and by considering two parameters as site-specific. This equation was fitted in one stage by the base-age-invariant dummy variables method. The system also incorporated an equation for predicting initial stand basal area, expressed as a function of stand age, site index, and the number of trees per hectare. This information can be used to establish the starting point for the projection equation when no inventory data are available. The effect of thinning on stand basal area growth was also analyzed and the results showed that the same projection equation can be used to obtain reliable predictions of unit-area basal area development in thinned and unthinned stands.

/pdf/modelling-stand-basal-area-growth-for-radiata-pine-9rsbevsxil.pdf

Modelling stand basal area growth for radiata pine plantations in Northwestern Spain using the GADA

This paper presents an assessment of the ability of the 3PG process-based model to simulate height (h) and diameter at breast height (DBH) growth in three plots located in a Eucalyptus globulus plantation on the Atlantic coast of Galicia (Northwest Spain). The obtained results show how this model estimates adequately height (h) and DBH growth, and determination coefficients (R
 2) between observed data and data predicted by the model are always higher than 0.97, root mean square error (RMSE) of 0.45–1.05 cm in DBH and 0.46–0.85 in h, and a model efficiency (EF) close to 1 (0.98–0.99). In order to improve the results predicted by the model, we propose modifying the nS and fullCanAge parameter values given by default so as to adjust growth rates in the plantation to the weather conditions in the site. The ability of the model to discriminate growth rates in the three plots must be noted, even when plots are located in the same plantation and they only show differences in aspects related to site factors. Given the obtained results in the three plots used in this study, its simplicity and the small number of parameters needed as input data, the 3PG model stands out as a very useful tool for forest plantation management.

Application of the 3PG forest growth model to a Eucalyptus globulus plantation in Northwest Spain

Un total de 17 funciones de perfil del tronco pertenecientes a seis categorias de modelos distintos (polinomicos simples, polinomicos segmentados, potenciales, exponenciales, de exponente variable y trigonometricos) se han ajustado a los datos de diametros medidos a diferentes alturas obtenidos de una muestra de 280 arboles de Pinus radiata D. Don en Galicia. Las ecuaciones obtenidas se han comparado y validado empleando una muestra independiente de 85 arboles, con el fin de determinar el modelo que mejor se adapta al perfil real del tronco para la especie en esta Comunidad Autonoma. Posteriormente se ha construido una tarifa de cubicacion con clasificacion de productos mediante integracion de la mejor funcion de perfil. Esta tarifa permite la estimacion del volumen del arbol correspondiente a los distintos destinos industriales de la madera y por tanto una mejor valoracion economica de la produccion de las masas de esta especie.

Construcción de una tarifa de cubicación con clasificación de productos para Pinus radiata D. Don en Galicia basada en una función de perfil del tronco

Tablas de producción de plantaciones de abeto Douglas en España

Se ha ajustado la funcion de densidad bivariante SBB a datos de altura y diametro de una muestra de pies de pino maritimo (Pinus pinaster Ait.) pertenecientes a 24 parcelas de ensayo instaladas en masas regulares de dicha especie y repartidas por toda la Comunidad Autonoma de Galicia. Utilizando una propiedad de la distribucion bivariante SBB se ha estimado la relacion altura-diametro en pino pinaster. Para ello se realizo un ajuste por regresion de medianas de la funcion SBB entre los datos de las alturas y los diametros de los pies de cada una de las 24 parcelas inventariadas. Los estimadores obtenidos en el ajuste tambien han servido para obtener las curvas correspondientes a los percentiles del 5 y 95%de la distribucion de alturas. Posteriormente, y a partir de la ecuacion modelizada, se ha construido una funcion altura-diametro generalizada, relacionando los parametros de la funcion SBB con las principales variables de masa.

Modelización de la relación altura-diámetro para Pinus pinaster Ait. en Galicia mediante la función de densidad bivariante SBB

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Construcción de una tarifa de cubicación con clasificación de productos para Pinus radiata D. Don en Galicia basada en una función de perfil del tronco

Tablas de producción de plantaciones de abeto Douglas en España

Modelización de la relación altura-diámetro para Pinus pinaster Ait. en Galicia mediante la función de densidad bivariante SBB