Hacia el manejo sostenible de los bosques de araar (Tetraclinis articulata (Vahl.) Mast.) en Túnez: modelos para las principales variables de árbol

The thuya (Tetraclinis articulata (Vahl.) Mast.) forests are one of the most important ecosystems in semiarid environments in north-western Africa, providing important economic profit and social services to local populations. However, lack of tools aiding sustainable management of these forests is detected. In the present work models for the main tree attributes as total height, crown diameter, height to crown base and stem form are developed for the species, using data from a net of plots installed in JbelLattrech region, in the NE Tunisia. Presented models allow characterizing the actual state and timber production of forests by using variables measured in typical forest inventories and conform a preliminary step for the future development of dynamic growth models.Los bosques de araar (Tetraclinis articulata (Vahl.) Mast.) constituyen uno de los ecosistemas más importantes de los ambientes semiáridos del noroeste de África, siendo además fuente de importantes beneficios económicos y servicios sociales a las poblaciones rurales. Pese a este interés, hasta el momento no se han desarrollado herramientas que faciliten la gesitón sostenible de estas masas forestales. En el presente trabajo se presentan modelos para los principales atributos de árbol individual: altura total, diámetro de copa, altura hasta la base de la copa y ecuación de perfil, desarrollados para la especie a partir de datos obtenidos en una red de parcelas permanentes instalada en la región de JbelLattrech, en el NE de Túnez. Los modelos presentados permiten caracterizar el estado y producción maderera actual de los bosques de thuya a partir de las variables medidas habitualmente en los inventarios forestales para la gestión, y constituyen además un paso preliminar para el desarrollo futuro de modelos dinámicos de crecimiento para la especie

Métodos alternativos de muestreo para estimar la estructura y caracteres reproductivos de bosques

Aleppo pine had a large forest cover in North Africa and along the Mediterranean basin which management is not fully developed and new forest tools are required. In this research, the forest structure, epidometric characteristics and allometric relationships were studied in 79 plots covering four bioclimatic zones from natural even aged forests of Aleppo pine located between eastern Algeria to the western coastal part of Tunisia. To characterize the forest structure three sampling methods were carried out: classical inventories (recording all pine trees), and two simplified approach using one average size or five dominant pine tree per plot. Annual growth increment and cone production were only calculated for the average size tree. Furthermore, the analysis of variance showed non-significant differences recorded between bioclimatic zones in trunk or crown diameter using the two simplified approach. Moreover, a significant decrease from wetter to drier areas in total height, crown height, cone seed production was observed only for average size tree method. However, the analysis of covariance showed significant differences between both approaches in total height, trunk diameter and crown coverage which were largely influenced by the pine tree density. In future investigations, we confirmed previous research that the dominant tree is a good sampling method to examine the site fertility, whereas the average size tree constitutes a valuable approach to study the population growth and reproduction.El pino carrasco muestra una gran cobertura forestal, tanto en el norte de África como en toda la Cuenca Mediterránea, cuyo manejo no está totalmente desarrollado lo que requiere nuevas herramientas de manejo. En esta investigación, se estudiaron la estructura forestal, las características epidométricas y las relaciones alométricas de 79 parcelas distribuidas a lo largo de cuatro zonas bioclimáticas en bosques regulares de pino carrasco situados entre el este de Argelia y la costa este de Túnez. Para caracterizar la estructura forestal se aplicaron tres métodos de muestreo: inventario clásico (midiendo todos los pies) y dos propuestas más sencillas, usando un árbol medio o cinco pies dominantes por parcela. El análisis de varianza no mostraba diferencias significativas de las mediciones de diámetro de tronco y de copa realizadas entre las distintas zonas bioclimáticas usando ambos métodos. Por otra parte, se observó una disminución significativa de las zonas más húmedas a las más secas en altura toral, altura de copa y producción de semillas fue observada aplicando el método de árbol medio. Además, el análisis de covarianzas mostraba diferencias significativas, usando ambas metodologías, en los valores medios de altura total, diámetro de tronco y cobertura de copa que mostraron estar influenciados por los valores de la densidad de arbolado de cada zona. Para futuras investigaciones, confirmamos estudios previos que apuntaban que la propuesta de muestreo de árboles dominantes como un buen método de muestreo para caracterizar la calidad de sitio mientras que la de árbol medio constituye una valiosa propuesta para el estudio del crecimiento de poblaciones y sus características reproductivas

Estimation allométrique de la biomasse du pin maritime en dune littorale : cas de la forêt de Rimel (Tunisie) -

Il existe de nos jours plusieurs raisons pour développer les méthodes d'estimation de la biomasse des peuplements forestiers méditerranéens, peu étudiés jusque là. En effet, la biomasse forestière constitue un point clé du cycle du carbone et son estimation devient nécessaire, notamment en prévision d'une utilisation accrue à des fins énergétiques et de l'augmentation du stockage de carbone en forêt. Cette étude a permis de déterminer les biomasses aériennes et souterraines d'un peuplement de pin maritime en Tunisi

Estimation allométrique de la biomasse du pin maritime en dune littorale : cas de la forêt de Rimel (Tunisie) -

International audienceIl existe de nos jours plusieurs raisons pour développer les méthodes d'estimation de la biomasse des peuplements forestiers méditerranéens, peu étudiés jusque là. En effet, la biomasse forestière constitue un point clé du cycle du carbone et son estimation devient nécessaire, notamment en prévision d'une utilisation accrue à des fins énergétiques et de l'augmentation du stockage de carbone en forêt. Cette étude a permis de déterminer les biomasses aériennes et souterraines d'un peuplement de pin maritime en Tunisi

Developing a stand-based growth and yield model for Thuya (Tetraclinis articulata (Vahl) Mast) in Tunisia

Thuya (Tetraclinis articulata (Vahl) Mast) is a Mediterranean forest species mainly occupying semiarid environments in North African countries, where it provides important ecological and economical services, such as biodiversity conservation, soil protection against erosion, fuelwood, timber for fencing, construction and handicraft, resins, etc. Despite the importance of the species, there is a severe lack of scientific knowledge as regards the management of these forests or modeling tools to support multifunctional forest management decision making. In the present work, we developed a stand-level integrated model for the management of Thuya forests in Tunisia. The model comprises a family of site index curves, built using the Generalized Algebraic Difference Approach (GADA) method, which provides predictions for stand growth, aboveground biomass, total and merchantable volumes, along with a non-linear system of stand level equations presented as stand density management diagrams (SDMD). The developed model has been used to define, characterize and compare four different management specific schedules for different site qualities and multifunctional objectives

Developing a stand-based growth and yield model for thuya (Tetraclinis articulata (Vahl) Mast) in Tunisia

Thuya (Tetraclinis articulata (Vahl) Mast) is a Mediterranean forest species mainly occupying semiarid environments in North African countries, where it provides important ecological and economical services, such as biodiversity conservation, soil protection against erosion, fuelwood, timber for fencing, construction and handicraft, resins, etc. Despite the importance of the species, there is a severe lack of scientific knowledge as regards the management of these forests or modeling tools to support multifunctional forest management decision making. In the present work, we developed a stand-level integrated model for the management of Thuya forests in Tunisia. The model comprises a family of site index curves, built using the Generalized Algebraic Difference Approach (GADA) method, which provides predictions for stand growth, aboveground biomass, total and merchantable volumes, along with a non-linear system of stand level equations presented as stand density management diagrams (SDMD). The developed model has been used to define, characterize and compare four different management specific schedules for different site qualities and multifunctional objectives. © SISEF

Variables de parcela, arbol y copa que afectan la produccion de piñas y piñones en bosques de pino carrasco de Tunez

In Tunisia, the Aleppo pine seed has a great importance, since in the last decades human consumption has risen considerable. Thus its regeneration and seed production capacities are important factors to take into account to reach the necessities of the country. To study the production of cones and seeds of Aleppo pine, Tunisia’s native Aleppo pine forests were surveyed in summer 2006, using 79 plots (40 × 25 m: 1,000 m²) spread over four bioclimatic zones. Stand and tree characteristics, crown dimensions and cone/seed variables were measured from an average tree of each plot (i.e. a total of 79 trees). Recorded data were submitted to simple and multiple regression analyses for explaining the variability in crown volume and crown surface, cone number and seed yield per average tree. Results showed a negative correlation between the stand density, crown characteristics and number of cones and seeds harvested from the average tree. For crown volume and surface, age, stand density, tree height, diameter at breast height, crown diameter and crown height were important explanatory variables under multiple regression analyses. For cone number per tree, only the age, stand density and total height were the most determinant variables. Matures cone number per tree and cone mass per tree were the most informative parameters for the total seed yields per tree. Finally, forest managers should know that crown size affects cone and seed crop of the Aleppo pine individual tree grown in Tunisia, but has no effects on seed number per cone and seed mass per cone