Pinus Halepensis Mill.) Stands in Northern Africa Be Oriented Towards Wood Or Seed and Cone Production? Diagnosis and Current Potentiality

Review Article ii FF o o r r e e s s t t doi: 10.3832/ifor2965-012 Biogeosciences and Forestry vol. 12, pp. 297-305 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 Wahbi Jaouadi (1-2), The aim of this work is to review studies on the silviculture of Aleppo pine (Pi- Souheila Naghmouchi (3), nus halepensis Mill.) in North Africa and the Mediterranean basin over a period (4) of 50 years. The study presents a synthesis of: (i) silviculture; (ii) wood pro- Moodi Alsubeie ductivity and growth; (iii) cone and seed production; and (vi) the socio-economic role of Aleppo pine. The results show that the production of the Aleppo pine is enhanced by the potential of the site, which is closely related to the bioclimatic stage and soil fertility. For instance, production increased from 0.4 to 4 m3 ha-1 yr-1 in an Aleppo pine stand with a dominant height varying between 9.7 and 22.8 m. Previous studies confirmed that the average maximum volume in annual growth of Aleppo pine is 3.3 m3 ha-1 yr-1 for 40-year old stands at good-fertility sites. The lowest values (<0.5 m3 ha-1 yr-1) were recorded for the fourth and last class of productivity in >100-year old stands. There is high demand for Aleppo pine seeds in North Africa, making their production profitable, and this represents an important sector for the sustainable development and improvement of living-standards of the local populations. There has been a steady increase in the demand for seeds across years, with seed production becoming a very promising niche. Silviculture oriented towards the commercial production of seeds is expected to enhance this species, as well as facilitate its preservation. Keywords: Aleppo Pine, Pinus halepensis Mill., Silviculture, Wood Production, Seed Production, Socio-economic Role Introduction et al. 2000), Italy (Ciancio 1986), Algeria annual rainfall. However, the species can- For centuries, Aleppo pine (Pinus halepen- (Bentouati 2006), and Tunisia (Souleres not withstand prolonged periods of frost sis Mill.) forests have been subject to heavy 1975, Souleres 1969, Chakroun 1986, Am- and is vulnerable to heavy snowfall, as its human pressure (clearing, illegal logging, mari et al. 2001, Sghaier & Garchi 2009, branches are fragile and easily broken (Ri- fires, pastures), leading to the degradation Sghaier & Ammari 2012). Because of its low codeau 2013). In Tunisia, Aleppo pine of plant cover. In addition, successive and requirements and high plasticity, Aleppo forests (Pinus halepensis Mill.) have funda- prolonged droughts cause the drying and pine has been extensively used as a refor- mental environmental, economic, and so- withering of standing trees. As for produc- estation species to restore degraded areas. cial roles. According to the last national for- tion and growth, the Aleppo pine has been Indeed, Aleppo pine is one of the few spe- est inventory (DGF 2010), pure stands of the subject of many studies in Mediter- cies that easily grows on poor and dry soils. Aleppo pine cover an area of 361,222 ha. ranean countries, particularly France (Be- In semi-desert regions, particularly in Libya, The average increase in height and diame- del 1986, Couhert & Duplat 1993), Spain this species is distinguished by its tolerance ter of this species does not exceed 7 cm (Montero et al. 2001), Morocco (Belghazi to drought, growing in areas with 250 mm year-1 and 0.25 cm year-1, respectively (Belg- hazi 1998). Many stands of Aleppo pine originate through reforestation activity. Since 1988, planting densities in Tunisia (1) Silvo-Pastoral Institute of Tabarka, University of Jendouba, BP 328, 8110 Tabarka -1 (Tunisia); (2) National Institute of Research in Rural Engineering, Waters and Forests, Univer- were reduced from 2500 to 1600 trees ha . sity of Carthage, BP. 10, Hédi Karray Street, Menzeh IV, Ariana 2080 (Tunisia); (3) Princess No- Consequently, because of the mechaniza- rah Bint Abdurrahman University, College of Sciences, Biology department, Riyadh (Saudi Ara- tion of soil preparation, particularly in the richest sites, the production of Aleppo pine bia); (4) Imam Muhammed bin Saud Islamic University, College of Sciences, Biology depart- 3 -1 -1 ment, Riyadh (Saudi Arabia) stands has increased from 6 to 8 m ha yr (Jalel 1996). @ Wahbi Jaouadi ([email protected]) @ Silviculture of Aleppo pine stands Received: Sep 28, 2018 - Accepted: Mar 16, 2019 Thinning Citation: Jaouadi W, Naghmouchi S, Alsubeie M (2019). Should the silviculture of Aleppo pine Thinning is a treatment used to improve (Pinus halepensis Mill.) stands in northern Africa be oriented towards wood or seed and cone the structure of growing forest stands. production? Diagnosis and current potentiality. iForest 12: 297-305. – doi: 10.3832/ifor2965- Thinning gives rise to woody samples or in- 012 [online 2019-05-27] termediate products that can be marketed. For a forest stand, thinning enhances the Communicated by: Tomás Vrska availability of water to trees (Breda et al. 1995, Ducrey & Huc 1999, Jiménez et al. © SISEF https://iforest.sisef.org/ 297 iForest 12: 297-305 Jaouadi W et al. - iForest 12: 297-305 y r 2008) and decreases the magnitude and years, depending on fertility classes. Furthermore, tillage associated with high t s duration of water stress (Aussenac 1987). Sghaier & Ammari (2012) showed that, for cover density facilitates the establishment e r According to Donner & Running (1986) and Aleppo pine in Tunisia, the age of operabil- of seeds. o Misson et al. (2003), thinning improves the ity for the first productivity class is about Acherar et al. (1984) showed that the col- F resistance of trees to drought, at least in 50 years, while it is 80 years for the second onization of Aleppo pines is restricted to a d n short term (within about 5 years of thin- class and exceeds 100 years for the third limited distance from the parent tree, with a ning). In fact, there is no ideal thinning class. just 3% of seeds falling more than 24 m s e regime across all forest stands, because from the parent tree. Seeds germinate c n each stand occupies a site with unique Silviculture of Aleppo pine stands after quickly, with the germination rate being e i characteristics. However, within the same fire high during the wet season. However, de- c s forest compartment, several successive Aleppo pine is very sensitive to fire, which spite the high mortality of young seedlings, o clearings are made before regeneration causes the cones to burst, thus facilitating especially in the first two years, the loss of e g method (Alaoui et al. 2011). Belghazi (1998) regeneration. Seed dispersal is favored by regenerated plants is compensated for by o i concluded that the periodicity of thinning wind and animals. Germination begins af- the production of large numbers of seeds B could be decided with a fixed rotation ev- ter the first rains, towards the end of sum- and the high germination rate (Acherar et – ery 10 years. Boudy (1952) observed that mer, and continues over the rest of the al. 1984). Quezel & Médail (2003) reported t s thinning rotation ranges between 6 and 15 year (Vennetier 2003). Following fire, natu- that, even in dense Aleppo pine forests, re- e r years, in general. Bentouati (2006) re- ral regeneration leads to the formation of a generation is not a problem, as long as o F ported that, in Algeria, the Aleppo pine has very dense thicket stage during earliest there is sufficient illumination. Bedel (1986) i a very high juvenile growth rate. This sug- years. This excessive density leads to slow showed that Aleppo pines are easily regen- gestion was confirmed by stem analyses, growth, caused by competition between erated, even on very degraded soils. Cer- which showed a gain in height of 20 cm young plants and a decline in stand vigor. tain factors, like grazing and repeated fires, year-1 during the first 40 years, 15 cm year-1 In this case, it is necessary to intervene as are likely to hinder the survival of young between 40 and 80 years, and a gradual soon as possible by implementing cleaning seedlings, weakening the success of natu- decline to 5 cm year-1 after 100 years. Mon- operations aimed to reduce the number of ral regeneration. To obtain medium and tero et al. (2001) used a rotation from 10 seedlings and regulate density. Interven- sufficient regeneration in Aleppo pine years when constructing Aleppo pine pro- tion in regeneration is obligatory in the forests, trees must be cut in the form of duction tables in Spain. Frantz & Forster young forest compartment, and improve- clumps, taking care to retain young trees (1979) adopted a rotation of five years in ment operations must be gradual and re- that carry many vital seeds. Beni-Imloul in Algeria. Couhert & Duplat peated at short intervals (Bentouati 2006). The selection of productive seed trees (1993) chose a variable rotation strategy must be evenly distributed on the cutting based on the fertility classes adopted in Management of Aleppo pine forests area and preserved for 3 to 5 years until a France. In Morocco, Alaoui et al. (2011) dis- Aleppo pine forests are managed as even- total regeneration is achieved. A density of tinguished two distinct periods of rotation aged forest. This type of treatment makes 50 pines per hectare is considered as the for thinning Aleppo pine stands: every five thinning interventions economically feasi- minimum threshold (D’hanens 1998). In years in reforested Aleppo pine stands and ble (Vennetier et al.

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