Peninsula, these two taxa are freely hybridized, and their taxonomy is somewhat confused, with each possessing a number of different nomenclatural identities (Castroviejo et al. 1990). Of the two taxa, Betula pubescens is the more oceanic, westerly distributed taxon while Betula pendula

In this paper we present a review of forest models developed in Spain in recent years for both timber and non timber production and forest dynamics (regeneration, mortality). Models developed are whole stand, size (diameter) class and individual-tree. The models developed to date have been developed using data from permanent plots, experimental sites and the National Forest Inventory. In this paper we show the different sub-models developed so far and the friendly use software. Main perspectives of forest modeling in Spain are presented.Key words: timber production; non-wood production; recruitment; modeling; forest. Resumen Modelos de crecimiento y producción en España: historia, ejemplos contemporáneos y perspectivasEn el presente trabajo se presenta una revisión sobre los modelos forestales desarrollados en España durante los úl-timos años, tanto para la producción maderable como no maderable y, para la dinámica de los bosques (regeneración, mortalidad). Se presentan modelos tanto de rodal completo como de clases diamétricas y de árbol individual. Los modelos desarrollados hasta la fecha se han desarrollado a partir de datos procedentes de parcelas permanentes, ensayos y el Inventario Forestal Nacional. En el trabajo se muestran los diferentes submodelos desarrollados hasta la fecha,

The taper functions of Kozak (1988), Bi (2000) and Fang et al. (2000) were comparatively analyzed in the present paper to develop a system for calculating the merchantable volume of oaks in the northwestern region of the state of Chihuahua (Mexico). Taper data corresponding to 298 trees were collected in mixed and uneven-aged pine-oak stands located throughout the study area, and covering the existing range of ages, stand densities and sites. Results show that the compatible segmented model developed by Fang et al. (2000) best described the experimental data and is therefore recommended for estimating tree diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for oaks. The equation developed in this study is a fundamental tool for use in forest surveys in the study region and is simple enough to ensure its operational implementation. The results of the statistical analysis show that the equation can be recommended for other regions, although some local adaptations may be needed.

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-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. stand basal area projection / stand basal area initialization / dummy variables method / generalized algebraic difference approach / thinning effect Résumé -Modélisation de la croissance en surface terrière de plantations de Pinus radiata dans le Nord-ouest de l'Espagne. Un système d'équations modélisant la croissance en surface terrière a été développé pour des plantations de Pinus radiata D. Don en Galice (Nord-ouest de l'Espagne) à partir des données recueillies dans 247 placettes mesurées entre une et cinq fois. Six équations dynamiques ont été analysées et des méthodes graphiques et numériques ont été employées pour comparer des modèles alternatifs. Une équation dynamique dérivée de la fonction de croissance de Korf, dont les deux paramètres spécifiques à la station sont estimés par l'approche de la différence algébrique généralisée (GADA), décrit le mieux les données. L'équation a été ajustée en une seule étape en utilisant la méthode des variables indicatives indépendantes de l'âge. En outre, pour prédire la surface terrière initiale, le système incorpore aussi une fonction de l'âge du peuplement, de l'indice de fertilité de station et du nombre d'arbres à l'hectare. Cette information peut être utilisée pour fixer l'état initial de l'équation de projection quand les données d'inventaire ne sont pas disponibles. L'effet de l'éclaircie sur la croissance en surface terrière a également été analysé et les résultats montrent que la même équation de projection peut être utilisée pour prédire de façon fiable l'évolution de la surface terrière dans les peuplements non éclaircis et les peuplements éclaircis. projection de la surface terrière / initialisation de la surface terrière / méthode des variables indicatives / approche généralisée de la différence algébrique / effet de l'éclaircie

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Understanding the spatial patterns of fire occurrence is key for improved forest fires management, particularly under global change scenarios. Very few studies have attempted to relate satellite-based aboveground biomass maps of moderate spatial resolution to spatial fire occurrence under a variety of climatic and vegetation conditions. This study focuses on modeling and mapping fire occurrence based on fire suppression data from 2005–2015 from aboveground biomass—expressed as aboveground carbon density (AGCD)—for the main ecoregions in Mexico. Our results showed that at each ecoregion, unimodal or humped relationships were found between AGCD and fire occurrence, which might be explained by varying constraints of fuel and climate limitation to fire activity. Weibull equations successfully fitted the fire occurrence distributions from AGCD, with the lowest fit for the desert shrub-dominated north region that had the lowest number of observed fires. The models for predicting fire occurrence from AGCD were significantly different by region, with the exception of the temperate forest in the northwest and northeast regions that could be modeled with a single Weibull model. Our results suggest that AGCD could be used to estimate spatial fire occurrence maps; those estimates could be integrated into operational GIS tools for assistance in fire danger mapping and fire and fuel management decision-making. Further investigation of anthropogenic drivers of fire occurrence and fuel characteristics should be considered for improving the operational spatial planning of fire management. The modeling strategy presented here could be replicated in other countries or regions, based on remote-sensed measurements of aboveground biomass and fire activity or fire suppression records.

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