A. Rojo

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

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.

Crecimiento y tablas de producción de Pinus radiata D. Don en Galicia

En este trabajo se exponen modelos de crecimiento y produccion de Pinus radiata D. Don en Galicia a partir de una sola medicion de parcelas de inventario, y del analisis de troncos de arboles dominantes y arboles tipo. Se obtiene un modelo de curvas de calidad de estacion polimorfico y tres tipos diferentes de tablas de produccion para otras tantas posibles evoluciones de la densidad de las parcelas. El turno de maxima renta en especie varia entre 28 y 44 anos, y el crecimiento medio de la masa principal a los 30 anos entre 8,1 y 19,8 m3/ha•ano. Se estima la produccion maderable segun el volumen a diferentes valores estandar del diametro final con corteza y se comparan las alternativas desde un punto de vista productivo.

Fijación de CO2 por Pinus sylvestris L. y Quercus pyrenaica Willd. en los montes «Pinar de Valsaín» y «Matas de Valsaín»

Se ha realizado una estimacion de la biomasa y del dioxido de carbono que hay acumulado en las masas de Pinus sylvestris y Quercus pyrenaica de los montes «Matas de Valsain» y «Pinar de Valsain» (Segovia). Para ello se han utilizado los datos de muestreos realizados por el CIFOR-INIA para ambas especies. Se eligen al menos tres pies por clase diametrica, se apearon y se separaron en fracciones de biomasa (fuste, ramas de diametro mayor de 7 cm, ramas de diametro entre 2 y 7 cm, ramas menores de 2 cm) que se pesaron en campo. Se extrajo el tocon de un pie por clase diametrica y se peso en verde. En laboratorio se determino el peso seco de las muestras y se hallaron modelos para las distintas fracciones que relacionasen la biomasa seca y con el diametro. Con estos modelos se calcularon unos valores modulares que se aplicaron a los datos del numero de pies, obtenidos de los inventarios, para estimar la biomasa total de los montes. El CO2 se estima mediante la relacion entre el porcentaje de carbono en la biomasa seca y la cantidad de carbono en una molecula de CO2. Se han realizado balances de fijacion neta de CO2 conociendo los crecimientos y las extracciones anuales.

Case Studies of Growing Stock and Height Growth Evolution in Spanish Forests

The objective of this chapter is to analyse the importance of the increment of forest growth rates in Spain during the last 150 years by giving a retrospective view of growth trends of Spanish forests. Two studies were carried out: (1) study of growing stock evolution of the Spanish forests during the past century; (2)study of forest growth evolution at site level of a forest in Central Spain. Data from inventories of large forests all around Spain are used for the first purpose and individual tree stem analysis data (Pinus sylvestris) from Central Spain are used for the second study. Through both studies it is possible to conclude that growing stocks and forest growth followed increasing trends. Increases in growing stocks were caused by changes in silvicultural practices, but changes in site productivity could be associated with changes in climatic and soil conditions. This chapter discusses the relationships between environmental factors and recorded growth increment, concluding that further research efforts are necessary to characterize the processes that drive growth changes.

Stem taper functions and volume equations with product classification for Pinus sylvestris L. in Galicia (NW Spain)

Twenty one taper functions from seven different groups of models (single polynomials, segmented polynomials, potential, exponential, variable exponent, trigonometric and logarithmic taper functions) were fitted to a sample of 1,694 diameter data. Diameter was measured at different heights of 163 Pinus sylvestris L. type trees of different ages and different site qualities from Galicia (Northwest of Spain). The adjusted equations were compared and validated through an independent sample of 565 data of diameter height from 73 type trees. A volume equation with product classification including the chosen exponential taper equation was developed.