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-eco- nomic 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 be- tween 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 pro- duction 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 to- wards the commercial production of seeds is expected to enhance this spe- cies, 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), annual rainfall. However, the species can- For centuries, Aleppo pine (Pinus halepen- (Bentouati 2006), and (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 (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 , University of , 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 , 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. 2010). A study by Ben- rugged relief, cutting should be conducted every 10 years in natural stands. In Tunisia, touati (2006) showed that the structure of in broad strips that are wide one to two 70% of Aleppo pine stands are less than 60 natural Aleppo pine forests is clumped in times the height of trees. When there is in- years old, with thinning practices reflecting Aurès-Algeria. Therefore, regeneration was vasive undergrowth of Aleppo pine, cop- this status (Sghaier & Ammari 2012). In Al- achieved by clear-cutting small areas in ma- picing is necessary. Once regeneration is geria, Bentouati (2006) suggested that ture stands. These cut surfaces in stands achieved, it is necessary to intervene start- thinning intervenes with the removal of grew as the seedling developed from 10 to ing from the 5th year by cleaning and elimi- dominant trees, benefitting future elite 20 years. nating poorly trained trees. This operation trees only. In France, Couhert & Duplat Chakroun (1986) proved that the even- aims to distribute seedlings optimally in (1993) recommended the use of high inten- aged forest regime in Tunisia is the most the space, enhancing the living space of sity thinning to eliminate almost 43% of appropriate for managing Aleppo pines, each individual and reducing the effect of trees from first class of fertility that are 43- because it is simple to apply. Nevertheless, competition. This approach allows future years old. In the Beni-Imloul massif in Alge- the spatial typology of stands, which is seedlings that establish to develop natu- ria, Frantz & Forster (1979) practiced inten- generally clumped, implies the differentia- rally, possibly facilitated by tillage (Neveux sive thinning, which was justified mainly tion of interventions according to stand ty- et al. 1986). because of the advanced age of most for- pology. While the basic unit of technical Regeneration is practiced by the localized est stands and because of the health status management in forest stands is the com- clearcutting of mature stands in small ar- of trees that had been attacked and in- partment, compartments are grouped into eas, which increase in size as seedlings de- fected/infested by insects and diseases. regeneration, improvement, and/or recon- velop, followed by a set of protection over stitution areas, according to use and typol- 10 years (Nsibi 1997). El Hamrouni & Sarson Age of operability of Aleppo pine ogy. The management planning period is (1975) showed that the density of seed stands usually 20 years in Tunisia. trees does not limit the natural regenera- The current annual increment (CAI) and tion of Aleppo pines, rather the rate of un- mean annual increment (MAI) curves con- Natural regeneration of Aleppo pine dergrowth recovery. Thus, reducing cover verge with age. The highest point of the forests causes the number of young pines to de- MAI is the age used to determine the age To regenerate Aleppo pine forests, seeds crease, making regeneration difficult. of operability of Aleppo pine stands in must be regularly spaced and removed Medium-density stands form canopies with management. It is possible to use this indi- from the influences of man and animals a more or less continuous cover, which de- cator (age of operability) to maximize (Nsibi 1997). In a study of the natural re- termines a microclimate favorable for seed wood production in forest stands (Clutter generation of Aleppo pine forests in Oum germination and seedling development et al. 1983, Davis & Johnson 1987, Davis et Jeddour (central Tunisia), Langley (1976) (Nsibi 1997). The authors also reported al. 2001). According to Chakroun (1986), showed that the natural dispersal of seeds that seeding in dense stands produces a the age of operability of Aleppo pines in was weak in Aleppo pine stands. Conse- relatively high density of natural seedlings Tunisia corresponds to an average diame- quently, spreading branches containing (i.e., from 2611 to 2739 seedlings ha-1, with a ter of 30 cm. According to Bentouati cones during thinning or clearcutting could density of more than 500 trees ha-1). (2006), this age is set between 70 and 90 increase the quantity of seeds dispersed.

298 iForest 12: 297-305 Silviculture of Aleppo pine stands in northern Africa

3 -1 -1 y

Stand density of Aleppo pines after bioclimate, and finally to 0.95 m ha yr in Aleppo pine is optimal at sites between 100 r t

regeneration a subhumid bioclimate. Sghaier & Ammari and 300 m a.s.l. (Vennetier et al. 2010). In s e

In the semi-arid conditions of Tunisia, (2012) showed that the average annual the French Mediterranean area and below r 3 Tschinkel (1976) demonstrated that the maximum growth of Aleppo pine is 3.3 m 600 m a.s.l., the Aleppo pine exhibits major o F most suitable spacing for the reforestation ha-1 yr-1 at 40 years old in good forest sites, variation in growth related to its ecological 3 -1 -1 d of Aleppo pine was 1.5 × 5 m, correspond- declining to less than 0.5 m ha yr for the requirements. It is generally well adapted n

-1 a ing to a planting density of 1300 plants ha . fourth and last productivity class (i.e., at an to most types of forest sites, except for hy- s

Sghaier & Ammari (2012) reported that, by age exceeding 100 years). Boudy (1950) dromorphic soils close to the surface. The e c

adopting average silviculture, stand den- and Chakroun (1986) stated that natural main factors influencing the growth of n e sity remained relatively high, exceeding forests of Aleppo pine have very low pro- Aleppo pine are related to the water bal- i

-1 c

600 stems ha for stands up to 80-90 years duction capacity, ranging from 0.5 to 3-4 ance of the forest site, while trophic bal- s of age. This high density might reflect the m3 ha-1 yr-1 at good forest sites. In compari- ance only has a marginal effect (Vennetier o 3 -1 -1 e fact that forests in Tunisia have always son, artificial stands produce 1.2 m ha yr et al. 2010). In Mediterranean forests, Alep- g

3 -1 -1 3 o been protected, with silviculture being ab- to 5.8 m ha year . For Aleppo pine at the po pine has an average growth of 3 to 5 m i

-1 -1 B sent in most stands. Ciancio (1986) showed reference age of 45 years, Ammari et al. ha yr (Ricodeau 2013). Ciancio (1986) re-

-1 3 – that a density of 2222 plants ha with a rec- (2001) estimated the total growing stock ported an average increase of 10 to 12 m t tangle layout (distance of 3 × 1.5 m) was to be 154.96 m3 ha-1 in fertility class 1, 71.52 ha-1 yr-1 at a good forest site in Italy. Soul- s 3 -1 3 -1 e the optimal density. Letreuch Belarouchi m ha in fertility class 2, 40.86 m ha in eres (1969) concluded that, in Tunisia, arti- r 3 -1 o

(1991) suggested that the optimal density fertility class 3, and 15.25 m ha in fertility ficial stands and stands resulting from fire F would be 1100 plants per hectare, with a class 4. These classes were characterized regeneration had much higher productivity i spacing of 3.5 × 2.5 m, reflecting that by a reference dominant height of 4.5 and than natural forests, while productivity stated in the National Reforestation Plan. 13.5 m. In addition, the average annual in- was lower in old stands. Tab. 1 presents the Bentouati (2006) suggested that the num- crement in volume ranged from 0.67 to 5.1 various studies on the growth of Aleppo ber of stems should be stabilized between m3 ha-1 yr-1, depending on the fertility of the pine that have been conducted in Tunisia 700 and 900 stems ha-1 for pines of 20 and forest site. Bentouati (2006) reported that and other countries, taking into account 30 years old, depending on the forest site. the Aleppo pine in Algeria was optimal at different classes of fertility and dominant This suggestion is justified by the fact that 50 years old, with growth in height signifi- tree height. Garchi (1991) showed that the the Aleppo pine is a light demanding spe- cantly slowing down by 80 years old. This fertility of Aleppo pine sites mainly de- cies, with high density stands generally be- finding is consistent with the observations pends on the depth of soil that can be ex- ing characterized by slow growth. For re- of Souleres (1969), who reported that the ploited by the roots, humus thickness, soil forestation, planting density is usually 1100 growth in height of Aleppo pine in Tunisia texture, and the relief. Forest sites on little stems ha-1 in the plains and 830 stems ha-1 slowed down between 50 and 70 years old, evolved soils with rich colluvial intake and a in the mountains (Alaoui et al. 2011). An in- depending on site conditions. Ciancio loam-clay texture have a fertility class 1, crease in density causes smaller spacing (1986) reported that the annual average in- and correspond to a site index of 13.5 to between trees, which leads to a decrease crement in Italy ranged from 1.9 m3 ha-1 yr-1 16.5 m tree height for 50-year-old trees. in growth (both diameters and height), at 25 years of age for the first fertility class Sites on calcareous brown soil and rend- due to inter-tree competition. Consequent- to 12.2 m3 ha-1 yr-1 at 50 years old. Pardé zine correspond to fertility class 2, with a ly, the volume and productivity of the en- (1956) documented a production of 4 m3 site index of 10.5 to 13.5 m for 50-year-old tire stand decreases (Cherak 2010). ha-1 yr-1 on soil of exceptional fertility at a trees. Sghaier et al. (2001) identified four forest site in France for stands aged 75 classes of fertility, with a reference height Productivity and growth of Aleppo years. In the Ouled Yagoub and Beni-Oud- of 45 years in descending order: class 1, pine forests jana ranges in Algeria, the average volume with a reference height of 13.5 m; class 2, An important characteristic of forest increase of sampled stands in pine forests with a reference height of 10.5 m; class 3, stands for silviculturists to be precisely ranged from 0.5 to 4.8 m3 ha-1 yr-1 (Ben- with a reference height of 7.5 m; and class documented is wood production (Garbaye touati 2006). 4, with a reference height of 4.5 m. The au- et al. 1970). Wood production corresponds The average maximum increase in volume thors concluded that about 49% of Aleppo to the volume of the tree, with and with- for all classes combined peaks at 2.8 m3 ha-1 pine stands in Tunisia belong to fertility out branches, under bark. Wood volume is yr-1 for the Ouled-Yagoub and Béni-Oudjana class 3. Akrimi (1984) and Garchi (1991) evaluated by scaling methods, using simple massifs in Algeria at the age of 80. In com- studied the production of Aleppo pine in parameters, such as diameter (or circum- parison, the same value was reached at an northwestern Tunisia (Sakiet region), ference) and height measured on well-cho- earlier age (<60 years) in stands in Spain. showing that the most important produc- sen trees distributed in the most represen- Furthermore, 2.6 m3 ha-1 yr-1 was docu- tion was between 0.4 and 4 m3 ha-1 yr-1 for a tative way at a site. Dominant height at a mented at a reference age of 50 years for dominant height (9.7-22.8 m). The second reference age is used to classify stands in a stands in Provence, France (Bentouati most important production was defined by fertility scale, and is closely linked to total 2006). In Morocco, the productivity of three classes of fertility, with the dominant production (Bentouati 2006). Many studies stands in Tamga for three classes of fertil- height being between 5 and 15 m. Couhert exist examining the productivity of stands ity reached an average value of 2.53 m3 ha-1 & Duplat (1993) stated that, to obtain a -1 across different countries in the Mediter- yr for stands aged around 75 years (Belg- high fertility class (Dominant height: Hdom= ranean (Pardé 1957, 1967, Decourt 1966, hazi et al. 2000). Serre-Bachet (1992) and 16 m at 50 years old), the age of exploita- 1973, Souleres 1969, 1975, Garbaye et al. Vila et al. (2008) investigated the structure tion is 80 years, following three major thin- 1970, Yi 1976, Ottorini & Nys 1981, M’hirit and growth of Aleppo pine in Jebel Man- nings at 30, 45, and 60 years. When consid- 1982, Toth & Turrel 1983, Couhert & Duplat sour, Tunisia, showing that rainfall en- ering total production and average annual 1993, Ammari et al. 2001, Sghaier et al. hanced growth, which was also closely as- increment, Aleppo pine stands belonging 2001, Sghaier & Ammari 2012). Souleres sociated to altitude and continentality. Guit to the first productivity class in Tunisia are (1969) showed that the production of et al. (2015) showed that altitude and expo- comparable to those belonging to the sec- Aleppo pine in Tunisia increased with the sure have a highly significant effect (P < ond productivity class in Spain and Algeria potential of the forest site, the bioclimatic 0.001) on the dominant height and density (Tab. 2). However, the average quadratic stage, and soil fertility. For an average of dendrometric parameters. Mérian & diameter of trees in Tunisia (38 cm), which basal area of 7 m2, the annual productivity Lebourgeois (2011) showed that there is a seems to be directly related to density increases from 0.67 m3 ha-1 yr-1 in an arid strong positive correlation between rainfall (Sghaier & Ammari 2012), is intermediate bioclimate to 0.82 m3 ha-1 yr-1 in a semi-arid and radial tree growth. The growth of between that of Algeria (42.5 cm) and iForest 12: 297-305 299 Jaouadi W et al. - iForest 12: 297-305 y r

t Tab. 1 - Maximum average increases for Aleppo pine for different classes of fertility and dominant heights (Bentouati 2006). (MAG): s

e Maximum average growth; (Hdom): dominant height; (Htot): average total height. r o F

Country Fertility Value MAG Authors Parameter 3 -1 -1 d (Region) class (m) (m ha yr ) n a

Couhert & Duplat (1993) France Hdom at 50 yrs 1 16 6 at 80 yrs s (Provence)

e 2 12 3 at 70 yrs c

n 3 8 1 at 60 yrs e i Pardé (1957) France Htot at 75 yrs 1 21 4 c s 2 18 3 o e 3 14 1.5 g

o Brochiero et al. (1999) France Hdom at 70 yrs 1 23.4 5 at 70 yrs i

B 2 20.1 3 at 50 yrs

–

3 16.7 2 at 30 yrs t s 4 13.4 1 at 20 yrs e r 5 10 - o F

i 6 6.7 -

Montero et al. (2001) Spain Hdom at 60 yrs 1 20 4 at 50 yrs 2 17 3.1 at 50 yrs 3 14 2.4 at 60 yrs 4 11 1.5 at 70 yrs

Belghazi et al. (2000) Morocco Hdom at 60 yrs 1 16.9 3.9 2 13.9 1.9 3 12.3 1.8

Frantz & Forster (1979) Algeria Hdom at 100 yrs 1 19 2.8 at 110 yrs (Béni-imloul) 2 16 2.21 at 50 yrs 3 13 1.6 at 120 yrs 4 10 1.10 at 130 yrs

Ammari et al. (2001) Tunisia Hdom at 45 yrs 1 13.5 3.44 at 45 yrs 2 10.5 1.59 at 45 yrs 3 7.5 0.91 at 45 yrs 4 4.5 0.34 at 45 yrs

Bentouati (2006) Algeria Hdom at 70 yrs 1 19 4.40 at 70 yrs (Oueld Yagoub, Béni Oudjana) 2 16 3.3 at 80 yrs 3 13 2.3 at 80 yrs 4 10 1.4 at 90 yrs

Spain (30.7 cm). Finally, El Khorchani productive characteristics of conifers (Gou- photosynthesis (Smith et al. 1988, Greene (2006) showed that the radial growth of bitz et al. 2002), seed dispersal (Benkman et al. 2002, Sutton & Staniforth 2002). Ayari Aleppo pine declined significantly from 1995, Lanner 1998), and sap levels (Moya et (2012), Ayari & Khouja (2014), Esis et al. 1950 to 2001, when investigating how cli- al. 2008) showed that several factors influ- (1965), and Greene et al. (2002) confirmed mate change affects the productivity of ence forest structure, including fire, ero- that the production of cones and seeds is this species. This decrease in the productiv- sion, and climate change (Fady et al. 2003). enhanced by a larger basal area. Thus, the ity of natural stands was attributed to in- In a study conducted in a natural Aleppo morphological parameters of trees influ- creased water stress caused by decreased pine forest at Jbel Mansour in Tunisia, Gar- ence on their reproductive capacity (Or- precipitation and increased temperatures. chi & Ben Mansoura (1999) showed that donez et al. 2005, Turner et al. 2007). Ayari the forest stand consisted of a small pro- & Khouja (2014) showed that a subhumid Production of cones and seeds portion (4.8%) of stems with an estimated bioclimate enhances cone production over Ayari (2012) showed that fructification is diameter at breast height (DBH) greater semi-arid climate. For instance, 117,036 better in subhumid stands compared to than 30 cm. Ayari et al. (2011a) showed cones ha-1 and 119.2 kg ha-1 of seeds were semi-arid stands, possibly because the that, in natural Aleppo pine forests in Tun- produced in a semi-humid stand, while scarcity of rainfall and water resources in isia, only 1.3% of trees had DBH > 30 cm. 8,960-54,376 cones ha-1 and 88.1-110.7 kg semi-arid stands. The subhumid environ- Mencuccini et al. (1995) and Castagneri et ha-1 were produced in a semi-arid stand. ment seems to offer higher yields in terms al. (2008) showed that the structure of the One hectare of Aleppo pine forest in the of the number and weight of cones and forest in Italy mainly depended on the geo- Kef region, Tunisia, was estimated to pro- seeds produced. These results are of great graphical variability of the forest site and/ duce 400 kg of cones every three years, practical interest, enabling foresters to or its density. Similarly, Ayari et al. (2011a) corresponding to 10 kg seeds (cone to seed make better decisions for future reforesta- showed that optimum seed production yield is 2.5% – MARHPT 2015). Ayari et al. tion programs. For instance, plantations in was achieved when trees are 8 m tall (2011b) showed that the weight of seeds subhumid areas should be oriented prefer- (height) with 8 m crown diameter, with per cones was 1.72 g in a sub-humid area, entially towards seed production, whereas any increase in height or crown diameter while it was 1.12-1.53 g in a semi-arid area. In plantations in more arid areas (semi-arid having a positive effect on the production comparison, seed production was 261.5 g and arid bioclimates) should serve other of cones and seeds. tree-1 in a subhumid area, while it was 118.4- purposes, such as the conservation of wa- Trees with large crowns might have bet- 166.2 g tree-1 in a semi-arid area. Cone ter and soil. Previous research on the re- ter light reception, improving the rate of weight per tree was 3.96 kg in a sub-humid

300 iForest 12: 297-305 Silviculture of Aleppo pine stands in northern Africa y r

Tab. 2 - Comparison of Aleppo pine production in Tunisia, Spain and Algeria (comparison at age 80 years) – Sghaier & Ammari (2012). t

-1 3 -1 s

(Dg): mean quadratic diameter; (N): number of stems ha ; (Hd): dominant height; (Vt): total volume (m ha ); (AAM): mean annual e increment (m3 ha-1 yr-1). r o F

Tunisia (class) Spain (class) Algeria (class) d Param n a

1 2 3 1 2 3 4 1 2 3 4 s

Dg 38.0 35.0 32.0 39.4 30.7 23.1 18.0 50.9 42.5 34.0 25.5 e c

N 248.0 201.0 149.0 246.0 408.0 684.0 862.0 169.0 197.0 237.0 300.0 n e Hd 15.9 12.8 9.6 20.0 17.0 14.0 11.0 20.7 17.5 14.2 10.9 i c s

Vt 250.9 142.8 66.3 285.1 230.1 185.7 113.8 350.1 264.1 184.3 107.5 o AAM 3.1 1.8 0.8 3.6 2.9 2.3 1.41 4.4 3.3 2.3 1.3 e g o i B

– area, while it was 1.6-2.4 kg in a semi-arid forests of Tunisia. Thus, slopes with these trend (GIZ 2014). t area. Finally, there were 160 cones per tree exposures should be selected in future re- The Aleppo pine is a very important for- s e in a sub-humid area, while there were 70- forestation efforts of Aleppo pine, to maxi- est species that forms an important com- r o

119 cones per tree in a semi-arid area. Ayari mize seed production. In Tunisia, the areas ponent of the national economy and hu- F et al. (2016) showed that there was an av- proposed for harvesting Aleppo pine cones man being in Tunisia. Aleppo pine seeds are i erage of 8-97 cones tree-1, with an average and seeds by the forest services range the product most sought after by con- cone weight of 15-20.6 g, the average cone from 60 to 100,000 ha in size. Overall, the sumers and farmers. The seeds represent weight per tree weight was 137.7-2018.6 g, national production of Aleppo pine seeds the main non-wood forest product at the and an average seed weight per tree of 7.3- (or zgougou) is in the order of 300 to 320 socio-economic level by regional and local 82. 9 g. Ayari (2012) showed that tree den- tons per year. The Governorate forestry services. In addition to their direct sity has a significant negative effect on the is the main region producing Aleppo pines, consumption as a pastry cream, several number and weight of cones and/or the with an average production of 100 to 120 products available on the market are based number and weight of seeds/cone. For in- tons of seeds per year. The Gover- on the Aleppo pine seeds, including yo- stance, production is almost halved when norate also has a center of production, ghurt, aromatic ice creams and vegetable the density of Aleppo pines in forests rises conservation, and marketing, with an an- oil. Aleppo pine seeds are a true national from 250 to 1000 trees ha-1. To enhance the nual production of 40 to 50 tons of seeds. wealth and source of income for many harvest of cones and seeds, Ayari (2012) The Kef Governorate produces just 10 families. In total, 2334 farmers harvest of suggested an optimal density of 250 trees tons per year, despite its importance in this product, employing 3000 seasonal ha-1. Ayari (2012) confirmed that the pro- terms of Aleppo pine coverage. At present, workers and generating about 625,000 € duction yield of cones and seed was less national consumption is estimated at 1.5 kg year-1 of revenue (MARHPT 2015). The col- important for stands with low densities seeds or 500 g of zgougou ground per fam- lection of cones for sale is a dangerous, and high basal areas. Furthermore, any in- ily per year, with an upward trend. Over though this activity generate an additional crease in diameter at breast height en- the next two years, an increase up to 2 kg income for workers. At the micro-enter- hanced profitability. Similarly, Smith et al. of ground zgougou per family per year is prise stage, zgougou businesses are prof- (1988), Arista & Talavera (1996), and Karls- expected (MARHPT 2015). The consump- itable. The exploitation of the Aleppo pine son & Orlander (2002) concluded that the tion of Aleppo pine seeds is a typical Tun- meets strict criteria, including the obliga- rate of fruiting in conifers is reduced in isian tradition, and is constantly increasing tion of specifications, the conclusion of op- stands with high density. The decrease in across years. The seeds are marketed erating contracts, and technical monitor- cone and seed production was explained throughout the country on the festival of ing. Seed extraction in an area of one ha is by a reduction in leaf photosynthesis activ- Mouled (a religious feast), and used to pre- estimated to return 32 €. Based on a selling ity (McDowell et al. 2000, Delzon et al. pare the zgougou cream, also known as As- price of 5 € per kg of seeds, the total rev- 2005). sida in Tunisia. Such cream is marketed in enue per hectare is estimated at 50 €. The Thus, reducing the density of Aleppo pine some pastries and, even, some restaurants, profit margin generated by one ha in one trees would enhance processes associated while ground seeds are marketed through- year out of three is of the order of 16 € ha -1 with regeneration and fruiting (Moya et al. out the year in grocery stores and super- (MARHPT 2015). In Tunisia, the cream pre- 2009, Ayari et al. 2010). Ayari (2012) markets. pared from the flour extracted from Alep- showed that the effect of tree age on cone po pine seeds, commonly called Assida and seed production is secondary to that Socio-economic role of the Aleppo zgougou, has an authentic flavor and con- of the dendrometric variables of the tree. pine in Tunisia firmed nutritional value based on its cal- Moreover, Ayari et al. (2011a, 2011b) In addition to its ecological role, Aleppo orific, lipid, and carbohydrate content. Ac- showed that altitude has a significant ef- pine in Tunisia has a significant productive cording to the National Institute of Con- fect on the number of seeds per cone and potential that should not be neglected, sumption in Tunisia (INC), 100 grams of As- the number of seeds per hectare. Thus, any given the size of the areas occupied by this sida, covered with a layer of cream and increase in ground elevation should lead to species. At the socio-economic and cultural dried fruit, provides nearly 595 calories, or heavier cones, with a weight gain of up to level, few studies have been conducted on 25% of the daily energy needed by an adult. 6.8 g between 250 m and 1185 m a.s.l. Aleppo pine, despite its multiple and di- Without ornamental substances, the nutri- (Ayari 2012). Regarding the effect of site verse uses, including the production of tional value of this same quantity is esti- exposure on fructification in conifers, Fer- seeds for human consumption. The deci- mated at 275 calories. rio et al. (2003) showed that slopes facing sion to consume Aleppo pine seeds is justi- NE, SE, S, and NW in a typical Mediter- fied by the specific taste of their aroma Suggestions to enhance seed ranean climate (characterized by optimal and by their high nutritional value (Way production temperatures, sufficient light and moder- 2006). In 2012, the national consumption of El Guemri (2018) showed that the refor- ate humidity) enhanced tree growth. Ayari seeds of the Aleppo pine was in the order estation density of Aleppo pine should be (2012) obtained similar results, showing of 300 to 320 tons, with a family consum- 1111 trees ha-1, because under these condi- that slopes facing NE, NW, S, and SE en- ing 1.5 kg of seeds or 500 g of ground tion, four times more Aleppo pine seeds hanced seed production in the Aleppo pine zgougou per year, with a predicted upward are harvested per hectare in the Northeast iForest 12: 297-305 301 Jaouadi W et al. - iForest 12: 297-305 y

r of Tunisia compared to the Northwest of ever, today, seed production represents a ternative sampling methods to estimate struc- t

s Tunisia. Thus, the reforestation of Aleppo very promising niche, especially for human ture and reproductive characteristics of Aleppo e pine forests in Tunisia. Forest Systems 20 (3): r pine trees should be directed towards seed consumption (pastry, ice creams, flour, o production in the Northeast of Tunisia and etc.). Aleppo pine seeds also have many 348-360. - doi: 10.5424/fs/20112003-10982 F oriented towards wood production in the other medicinal and cosmetic uses, and Ayari A (2012). Effets des facteurs environne- d n Northwest of Tunisia. Several factors had a high added value. Sylviculture oriented to- mentaux sur la fructification de pin d’Alep (Pi- a combined effect on Aleppo pine seed/cone wards the commercial production of Alep- nus halepensis Mill.) en Tunisie. [Effects of envi- s e production in natural forests growing in po pine seeds could only enhance the im- ronmental factors on the fruiting of Aleppo c

n Tunisia. Ayari et al. (2011a) suggested that portance of this species in Northern Africa. pine (Pinus halepensis Mill.) in Tunisia]. Thèse e i bioclimatic areas with higher moisture con- de doctorat en Science Biologique, Faculté des c s ditions have a positive effect on fructifica- References Sciences de , Tunisie, pp. 230. [in French] o tion, producing greater cone crops and Acherar M, Lepart J, Debussche M (1984). La [online] URL: https://www.researchgate.net/pu e g seed yields. The sub-humid zone produces colonisation des friches par le pin d’Alep en blication/260185216 o i greater quantities of cones and seeds (with Languedoc méditerranéen [Colonization of old Ayari A, Khouja ML (2014). Ecophysiological vari- B higher mean yields) compared to other bio- fields by Aleppo pine in a Mediterranean part ables influencing Aleppo pine seed and cone – climatic areas in Tunisia. Geographical vari- of France]. Acta oecologica 5 (2): 179-189. [in production: a review. Tree Physiology 34: 426- t s ability of the bioclimatic areas is associated French] [online] URL: http://geoprodig.cnrs.fr/ 437. - doi: 10.1093/treephys/tpu022 e r with the latitude, longitude, elevation, and items/show/159516 Ayari A, Meftahi M, Zammeli F, Khouja ML o

F land aspect (Ayari 2012). Akrimi N (1984). Relations entre production et (2016). Seed production variability of Aleppo i Overall, longitudinal gradients represent sols dans la pineraie de Sakiet Sidi Youcef (Tun- Pine (Pinus halepensis Mill.) within Korbus Ar- the strongest geographical determinant isie septentrionale) [Relations between pro- boretum (North East of Tunisia). Global Journal causing a marked increase in cone dimen- duction and soils in the pine plantation of of Botanical Science 4: 20-23. - doi: 10.12974/23 sions and seed content, mainly in the semi- Sakiet Sidi-Youssef (Northern Tunisia)]. Ph.D. 11-858X.2016.04.01.3 arid zone. High consistency was found re- thesis, University of Aix-Marseille, France, pp. Bedel J (1986). Aménagement et gestion des pe- garding the effect of elevation and longi- 179. 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