Alternative sampling methods to estimate structure

Abstract

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.Key words: Pinus halepensis Mill.; bioclimatic zones; forest structure; sampling approach; increment; reproductive characteristics. ResumenMétodos alternativos de muestreo para estimar la estructura y caracteres reproductivos de bosques de pino carrasco en Túnez 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...

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

“…In other forest areas of Aleppo pines, Harfouche et al (2003) reported an increase in mean individual seed mass related to a coastal gradient on the Mediterranean coast of North Africa, but this was due to the confounding effect of latitudinal effects. A negative elevation effect on cone size was found in this study, confirming the previous results obtained by Ayari et al (2011b) in the forests of northeastern Tunisia, Boulli et al (2001) in Aleppo pine forests in Morocco and Climent et al (2008) in many Mediterranean countries, including Tunisia. In this study, the production of wood, cones and seeds were altitude sensitive; these results were confirmed by Ayari et al (2011c) who showed that the predictive models obtained showed that the elevation had an effect on the size of the cone.…”

“…Our research shows that altitude is negatively correlated with the production of Aleppo pine to sub-humid bioclimate; these results are not in agreement with Turner et al (2007) who showed for a similar species, Pinus contorta, the positive effect of elevation on cone/seed production that was attributed to shorter drought periods associated with more abundant rainfall. Our study show that exposure north, north-east, north-west, south, south-east, south-west have a positive correlation with the production of wood, cones and seeds, which confirm the findings of Ayari et al (2011b), showing favourable cone harvesting and seed yield in forests on favourable aspects, such as north-east, south-east south and north-west This could be explained by the higher availability of light and temperatures during the pollination period, which seems to play a major role in promoting conifer breeding success in the same way as other species (Hylander, 2005). Our results do not support the results of Schiller and Atzmon (2009) who concluded that higher egg abortions and lower pollen vigour and viability were found in the north, south, south-west and west aspects, favouring subsequent mortality from cone formation or leading to empty seeds (Schiller, Atzmon, 2009).…”

Should the silviculture of Aleppo pine (Pinus halepensis Mill.) stands in northern Africa be oriented towards wood or seed and cone production? Diagnosis and current potentiality

“…Overall, longitudinal gradients represent the strongest geographical determinant causing a marked increase in cone dimensions and seed content, mainly in the semiarid zone. High consistency was found regarding the effect of elevation and longitude on cone dimensions and average individual seed mass (Ayari et al 2011b). The effect of the geographical distribution on fructification is greater under drought conditions (Schiller & Atzmon 2009).…”

“…One hectare of Aleppo pine forest in the Kef region, Tunisia, was estimated to produce 400 kg of cones every three years, corresponding to 10 kg seeds (cone to seed yield is 2.5% -MARHPT 2015). Ayari et al (2011b) showed that the weight of seeds per cones was 1.72 g in a sub-humid area, while it was 1.12-1.53 g in a semi-arid area. In comparison, seed production was 261.5 g tree -1 in a subhumid area, while it was 118.4-166.2 g tree -1 in a semi-arid area.…”

“…Ayari (2012) showed that the effect of tree age on cone and seed production is secondary to that of the dendrometric variables of the tree. Moreover, Ayari et al (2011aAyari et al ( , 2011b showed that altitude has a significant effect on the number of seeds per cone and the number of seeds per hectare. Thus, any increase in ground elevation should lead to heavier cones, with a weight gain of up to 6.8 g between 250 m and 1185 m a.s.l.…”