Stand, tree and crown variables affecting cone crop and seed yield of Aleppo pine forests in different bioclimatic regions of Tunisia

Abstract

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.Key words: Aleppo pine; crown dimensions; cone number; seed yields; bioclimatic zones; Tunisia. ResumenVariables de parcela, árbol y copa que afectan la producción de piñas y piñones en bosques de pino carrasco de Túnez En Túnez, la producción de piñones del pino carrasco tiene una gran importancia, ya que en las últimas décadas su consumo ha aumentado de forma considerable. Por ello, su regeneración y capacidad de producción de piñas/piñones en un factor a tener en cuenta en Túnez. En verano del 2006 se eligieron 79 parcelas de 1.000 m² (40 × 25 m) situadas en cuatro zonas bioclimáticas representativas de Túnez para el estudio de la capacidad de producción de piñas/piñones del pino carrasco. Teniendo en cuenta todos los árboles de las parcelas, se identificó el árbol promedio, del que posteriormente se medirían variables de árbol, dimensión de copa y producción de piñas/piñones. Los resultados demuestran una correlación negativa entre la densidad de la parcela, características de la copa y el número de piñas/piñones recolectados por cada árbol promedio. Para la descripción del volumen y superficie de copa, las variables más importantes fueron edad, densidad de parcela, altura y diámetro del árbol, y altura y diámetro de la copa. Las variables edad, densidad de parcela y altura del árbol fueron las más significativas para la determinación de nú-mero de piñas por árbol. Para el cálculo del total de piñones por árbol, las variables más informativas fueron el nú-mero ...

Considering evolutionary processes in adaptive forestry

“…As indicated in Fig. 2, this allocation is influenced by local stand density as well as other practices like pruning (Ayari et al 2012). Thinning and pruning also affect the plasticity, which will interact with selection processes as previously mentioned: The question here is whether the plastic response induced by the silviculture is adaptive or maladaptive regarding future climate change.…”

Morphometrics of Pinus patula crown and its effect on cone characteristics and seed yield in Kenya

“…Some studies have observed that cone production by Pinus spp. (Pinus halepensis and Pinus sylvestris) is not uniform and often varies among compartments within the crown (Ayari et al, 2012;Abdelaziz Ayari and Khouja, 2014;Iwaizumi et al, 2008). These variations are considered to be associated with resource-related factors such as collection practices, crown size, stand density, and light intensity (Iwaizumi et al, 2008).…”

Morphological characteristics and variation of wood, cone and seed productions in the reforestation of Aleppo pine in Northeastern Tunisia using terrestrial and spatial index approaches

“…We found that basal area is positively correlated with pine production in this sense. Ayari et al (2011aAyari et al ( , 2012a, Mencuccini et al (1995) and Arista and Talavera (1996) showed that basal area had a positive influence on seed and cone productions (Tunisia, Italy, Spain). Ayari et al (2011c) showed that the seed and cone productions increased with an increase in tree height, DBH and age (Tunisia).…”

“…Goubitz et al (2004), Moya et al (2008b) and Verkaik and Espelta (2006) found that the level of cone serotiny decreased with an increase in tree height (Israel, Spain). Ayari et al (2012a), Girard et al (2012) and Malcolm et al (2001) showed that the seed and cone productions increased with an increase in tree crown height and tree crown diameter (Tunisia, France). Dendrometric measurements have been confirmed as easier and less costly estimators for Aleppo pine forests in the southern Mediterranean Basin, which have been described as more vigorous in growth and fruiting than the northern or eastern Mediterranean populations (Climent et al, 2008).…”

“…10% of the country's population) live in forest areas and benefit from its resources (Gader, 1999). The Aleppo pine forests play a crucial role in the reforestation of degraded environments and soil fixation, as well as the national economy and the human well-being (Ayari et al, 2012a). The Aleppo pine trees have multiple and diversified uses such as the exploitation of wood, tannin and seeds (Ayari et al, 2011a).…”