Gregorio Montero

Analysis of diameter-density relationships and self-thinning in non-thinned even-aged Scots pine stands

Abstract Self-thinning and size–density relationships in non-thinned even-aged Scots pine stands in Spain were studied. Data from nine thinning experimental areas located in natural and artificial stands were used with a total of 23 untreated or control permanent plots. Three different diameter–density expressions were fitted and compared: the Reineke’s equation, the modification of this expressions proposed by Zeide [Zeide, B., 1995. For. Ecol. Manage. 72, 265–272], and the self-thinning model developed by Tang et al. [Tang S., Meng, C.H., Wang, Y.H., 1994. For. Ecol. Manage. 70, 67–73]. Results indicate that self-thinning in Pinus sylvestris L. follows a concave down line whose slope increases with stand density until it takes as its asymptote the straight line of maximum density. The slope of this straight line obtained for Scots pine stands in Spain is −1.75.

Acorn production in Spanish holm oak woodlands

We present a review on the state-of-the-art of fruit prodution in Western Iberia woodlands («dehesas»), and particularly in Q. ilex (holm oak) «dehesas». This threatened ecosystem is of very high ecological and economical importance. Quercus sp. fruits (acorns) are essential for wildlife, and for pig fattening in «dehesas». In the first part of this review we briefly describe the phenology of the holm oak and the factors affecting acorn morphology and chemical composition. In the second half we analyze the main known factors reported in the literature that determine acorn production: pruning, stand characteristics, and site (weather and soil). We make several suggestions to improve future research and detect the existing gaps in the undertanding of acorn production. Fruit production is highly variable, both between and within years and individuals. The mean production in «dehesas» (mean density circa 50 trees/ha) is around 250-600 kg/ha (≈100 g/canopy-m, CV > 100%). Acorn morphology is also very variable, with mean sound acorn size around 3.5 × 1.6 cm, CV ≈ 10% (3.5 g/acorn, CV > 50%). Silviculture plays an essential role in acorn production. Acorn production per tree seems to be negatively related to density. The effect of pruning is less clear: production seems to be reduced in the first and second years after pruning. After the third year it is not possible to discern from the literature whether there is any response to pruning or not. Weather and soil (site) also impact production and their effects should be explored in future management. The influence of genetics is unknown and should also be addressed. Longer data series are necessary. The dasometric features of the stands need to be characterized, in order to better understand production and compare results from different locations. Much research is still required to understand the functioning of fruiting in these woodlands.

Cone and seed production from stone pine (Pinus pinea L.) stands in Central Range (Spain)

Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.

Thinning intensity and growth response in SW-European Scots pine stands

The effect of different thinning intensities on growth and yield was studied in Pinus sylvestris L. stands at the south-western limit of its distribution area (Central Spain), using five long-term thinning trials. Data were analysed collectively considering several factors (trial, block, plot and period) as random effects. Total volume and volume increment decreased with thinning intensity, this loss being more significant in the case of moderate and heavy thinning. No difference was found among treatments for total basal area or the increment in basal area. The results revealed an optimum basal area (Assmann’s definition) between 85 and 100% of the basal area in unthinned plots. Volume growth loss associated with heavy thinnings (reduction of 18% in volume increment) was smaller than that reported in Central and Northern European regions (greater than 25%). Height increment was not influenced by thinning, whereas dominant and quadratic mean diameter increments increased with the thinning intensity. The response of diameter growth to thinning was greater at younger ages (less than 50 y) and in medium-sized trees.RésuméL’effet de différentes intensités d’éclaircie sur la croissance et la production de peuplements de Pinus sylvestris L. a été étudié à la limite sud-ouest de sa zone de répartition (centre de l’Espagne), à partir de cinq essais d’éclaircie suivis à long terme. Les données ont été analysées collectivement en prenant en compte différents facteurs (essai, bloc, placeau et période) comme facteurs aléatoires. Le volume total et l’accroissement en volume diminuaient avec l’intensité d’éclaircie, cette perte devenant plus significative dans le cas d’éclaircies modérées et fortes. Aucune différence n’a été trouvée entre traitements pour la surface terrière totale ni pour sa vitesse d’accroissement. Les résultats révèlent un optimum de surface terrière (selon la définition d’Assmann) compris entre 85–100 % de la surface terrière des placeaux non éclaircis. Les pertes de croissance en volume associées aux éclaircies fortes (réduction de 18 %) étaient plus faibles que celles qui sont rapportées pour les régions du Centre et du Nord de l’Europe (supérieures à 25 %). L’accroissement en hauteur n’a pas été influencé par l’éclaircie alors que l’accroissement quadratique moyen en diamètre augmentait avec l’intensité d’éclaircie. La réponse en termes d’accroissement en diamètre à l’éclaircie a été plus forte pour les jeunes arbres (moins de 50 ans) et les arbres de taille moyenne.

Site index model for Pinus sylvestris in north-east Spain

Abstract The McDill–Amateis difference model and difference forms of the Chapman–Richards, Hossfeld, Lundqvist–Korf and Schumacher growth models were derived to model the dominant height growth of Scots pine (Pinus sylvestris L.) in north-east Spain. Data from permanent sample plots and stem analysis were combined and used for modelling. Both qualitative and quantitative criteria were used to compare alternative models. The PRESS (prediction sum of squares) statistic was used to analyse the predictive ability of the models. The polymorphic difference equation derived from the Hossfeld function resulted in the best compromise between biological and statistical aspects, producing the most adequate site index curves. This dynamic equation can compute predictions directly from any age-dominant height pair without compromising consistency of the predictions. The predictions of dynamic equations are unaffected by arbitrary changes in base-age. The presented Hossfeld equation is recommended for site classification and dominant height prediction in Scots pine stands in north-east Spain.

Growth and Yield Models for Pinus halepensis Mill

A partir de los datos obtenidos de 72 parcelas instaladas en 1965, en masas repobladas de Pinus halepensis, inventariadas en 1965, 1970, 1975, 1980, 1988 y 1999, se han elaborado modelos de crecimiento y produccion de selvicultura encontrada para cuatro calidades de estacion. Las curvas de calidad se han definido por la altura dominante alcanzada a los 80 anos de edad y se han ajustado por el modelo de Richards, resultando las siguientes curvas: calidad 20, calidad 17, calidad 14 y calidad 11. Posteriormente se han elaborado modelos de produccion de selvicultura variable incluyendo dos regimenes de claras, simulados a traves de la variacion del indice de Hart-Becking, para las calidades 20 y 17, que son las que presenta un mayor interes productivo. Para las calidades 14 y 11 se representan tablas con un unico regimen moderado de claras, como corresponde a su mayor interes protector y su menor interes productivo.

The Pinus pinea L. woodlands along the coast of South-western Spain: data for a new geobotanical interpretation

The origin and natural range of the Stone pine (Pinus pinea L.) has been questioned for more than a century. In this work, we focus the investigation on one of the most important and controversial regions, viz., the Iberian Peninsula and, specifically, the Huelva and Cadiz populations in Andalusia, one of the most representative population cores. Although some authors maintain that it is an autochthonous Iberian species, most of them consider it to be exotic. From this idea, many works have been done and a sintaxonomic scheme has been created, which is accepted by the majority of the scientific community, not including Pinus pinea, nor its formations, since they are considered as man-induced forest crops. However, Stone has been present for several thousand years in the Iberian Peninsula and in the territory studied, as several paleobotanic and historical data show, proving that Pinus pinea is an autochthonous species of this region. This is a clear consequence to the field of geobotany, since – at least – the Stone pine woodlands from the Iberian Southeast must be considered as communities predominated by an autochthonous species that must be included in the sintaxonomichal schemes.

Silviculture and dynamics of Pinus sylvestris L. stands in Spain

En este trabajo se presenta informacion sobre ecologia, tipologia, selvicultura, produccion, dinamica y biodiversidad de los pinares de Pino silvestre en Espana. Inicialmente se realiza una descripcion de la distribucion y tipos de masa de Pino silvestre y de sus aspectos climaticos y edaficos mas importantes. En segundo lugar se presenta una tipologia de las masas naturales en la Peninsula Iberica. Posteriormente se tratan los aspectos mas importantes de la selvicultura de la especie, incluyendo los objetivos de la ordenacion de sus masas en Espana. En el apartado de produccion se aporta informacion relativa de su produccion potencial ademas de una tabla de produccion para las cinco calidades de estacion definidas en Espana. Se tratan las diferentes etapas de sucesion natural de las masas del pinar asi como los tratamientos o practicas selvicolas mas comunes en Espana. Por ultimo se hace una breve referencia de los efectos de la selvicultura aplicada en la biodiversidad de estas masas forestales.

Revisión: Índices de diversidad estructural en masas forestales

La estructura es un buen indicador de la biodiversidad del sistema y es facilmente modif icable a traves de la selvicultura, por lo que su adecuado conocimiento es indispensable para garantizar una gestion sostenible. En este trabajo se presenta una revision sobre el analisis de la diversidad estructural en masas forestales. El estudio de la diversidad estructural de un bosque se puede abordar desde un punto de vista estatico y dinamico. En primer lugar se describen y discuten los principales indices que caracterizan desde un punto de vista estatico los tres aspectos de la estructura de un rodal: distribucion espacial, diversidad y mezcla de especies y diferenciacion. Para cada uno de estos tres aspectos se incluyen indices tanto espaciales como no espaciales. Posteriormente se analizan los indices de diversidad estructural conjunta, que valoran de manera global los tres aspectos de la estructura del rodal antes considerados, incluyendo en algunos casos una estimacion de la madera muerta. Finalmente se revisan los trabajos que realizan un analisis dinamico de la diversidad estructural, generalmente basados en el estudio de la evolucion en el tiempo de los indices estaticos. Se comentan las tres metodologias con las que se puede acometer este estudio: parcelas localizadas en las distintas fases de desarrollo del ciclo de la masa, parcelas permanentes y modelos de crecimiento que simulen la estructura del rodal.

An operative framework for total hicksian income measurement: application to a multiple-use forest.

A methodology for estimating total hicksian income in multiple-use forests is presented. The approach consistently incorporates commercial as well as non-commercial economic values and enables the measurement of national accounting aggregates taking into account variation in man-made and natural capital. Innovative solutions are developed (i) for the estimation of non-market values, such as recreation, where an attempt to determine exchange values has been made simulating markets, (ii) for timber, where standing timber valuation methods have been extended to cover uneven stands, and (iii) for carbon fixation valuation, where only permanently fixed carbon after 1990 has been taken into account. The methodology is applied to a multiple-use pinewood in the Guadarrama mountains, near Madrid (Spain). Timber, cattle grazing, hunting, recreation, carbon fixation and conservation values are measured and integrated in the accounting system, using primary microeconomic data from the case study. Results indicate the importance of non-commercial income, which accounts for 51% of the total income, and the social relevance of the analysed forest, implying that only 31% of the total income generated is appropriated by the forest owner.