Data collection and statistical analyses

In May 2012, February 2014 and March 2016 (Spanish trials) and in March 2016 (Tunisian trials) the main variables related to tree and scion status and growth and presence of cones were evaluated: Tree survival (alive vs. dead), Scion status (viable vs. unsuccessful, considering only alive grafted trees), Basal tree diameter, Diameter at graft point, Total tree height, Height of graft point, Crown diameter, Number of 1 year-old conelets (only in 2016), Number of 2 year-old and of ripe 3 year-old cones.

In the case of P halepensis, the number of conelets and cones were evaluated only when the scion was alive.

Statistical analyses of tree survival, scion viability after successful nursery grafting, on-field grafting success and number of cones were descriptive: mean number of trees in each category. Dasometric data (diameters and heights) were analyzed with analysis of variance (Anova) using SPSS soft-ware, considering that two treatments were different when p < 0.05.

III – Results and discussion

In general, tree survival was high, 76% (60-98%) in Spain and 80% (74-82%) in Tunisia, except in the poorest sites, El Azib, Tunisia (42%) and Capçanes, Spain (47%), the latter affected also by dam-age from wildlife browsing. No evident effect of rootstsock species or provenances was observed.

More than 90% of alive trees grafted in nursery kept the scion alive trials after three and four veg-etative seasons in Tunisia and Spain (Freixes and Monestir) trials.

In the Spanish trials, on-field grafting success was lower for Pinus halepensis (15%) than for Pinus pinearootstocks (64%), as shown in Fig 2. Grafting success was proportional to the suitability of the rootstock to the site: the sites that were more adequate for Pinus pinea(Freixes, Monestir) showed, for this species the best rootsock performance, while the sites more suitable for Pinus halepensis(Marçà, Serra d’Almos) had the highest grafting success rates for this species. Cap -çanes trial, with very poor quality and suffering from wildlife browsing, showed the poorest results of all sites. No clear pattern of rootstsock provenance or scion clone was observed. The poorer per-formance of Pinus halepensisrootstocks compared to P. pineaones was also observed, for the same vegetative materials, during nursery grafting (Piqué et al., 2013), which was probably linked to the excessive slenderness of the former.

Fig. 2. On-field grafting success in Spanish field trials, four years after grafting, for each root-sock species. The number below each bar indicates the number of grafts performed.

With regard to the tree basal diameter and total height, we found no consistent significant diffe rences between rootstock species, provenances or treatments. However, in the Spanish field trials

“Monestir” and “Freixes”, a slight trend of Tunisian rootstocks growing more than Spanish ones was observed, while nursery-grafted scions tended to grow more than on-field grafted ones. Overall mean basal diameter of Pinus pineaand Pinus halepensiswas 36 and 40 mm, respectively, ave rage total height 98 and 138 cm, respectively, considering all field trials together.

The percentage of successfully grafted trees with cones was higher on P halepensisrootstocks (29-83%) than on P pinea(10-40%), while no major effect of provenances or grafting treatment (Spanish field trials) was observed (Fig. 2). Ungrafted Pinus pineatrees (i.e. those that were not grafted and those whose grafting was unsuccessful) presented no cones. The higher growth and earlier cone production of Pinus halepensis rootstocks compared to P. pinea ones contrasts with findings by Gordo et al. (2013) who observed the opposite trend, though with quite different soil conditions (arensols) in central Spain where Aleppo pine is not native.

Considering the number of conelets, it seems that this number had increased over time (Fig. 3).

Spanish plots (4 years-old) showed similar cone production as Tunisian plots (3 years-old), when correcting the age difference (i.e. number of cones 2 years after grafting). The only exception was in Monestir site, which showed a notably higher production than the rest of the other trials. In Spain, the effect of provenance and grafting treatment (nursery vs on-field) on the cone production was not consistent, but it seems that in general P. halepensisrootstocks tended to induce more cones.

Fig. 3. Percentage of successfully grafted trees with cones of each cohort. The number above each bar indicates the average number of cones/coneletsof the given age on each tree. Spanish trials were 4 years old while Tunisian ones were 3 years old.

IV – Conclusions

Survival of trees and scions depended on site quality, especially climatic conditions, and on the avoidance of browsing damage. This emphasizes the importance of an adequate choice of the planting area and of the consideration of tree protection. In general, grafted Pinus pinea planta-tions in Spain and Tunisia showed high survival and promising growth rates, both with P. pinea and P. halepensis rootstocks, on medium quality sites. Grafting clearly advances cone production com-pared to ungrafted trees, which after 3-4 years did not form any cone.

On-field grafting success was lower for P. halepensis than for P. pinearootstocks, being particu-larly lower in the hardest site conditions.

Most trees grafted in nursery kept the scion alive after field plantation. In the case of on-field grafting, the success rate was adequate (>50%) in P. pinea on medium quality sites, while it was very poor in poor quality sites subject to severe drought. On-field grafting on P. halepensisled to poor results, particularly in the sites where this species was less adapted.

There were no significant effect of the rootstock species or provenance on tree growth.

Regarding cone and conelets production, the results from Spanish and Tunisian field trials showed a generally similar trend, with Pinus halepensisrootstocks leading to higher cone production than Pinus pineaones, although no major effect could be attributed to the different provenances. In the two field trials where both nursery and on-field grafting were performed, we found no major dif-ference in cone production.

References

Bono D., Othmani H., Ammari Y., Piqué M. and Aletà N., 2013.Characterization of Pinus pineaL. and P.

halepensisMill. provenances from Spain and Tunisia related to their rootstock use. In: Options Méditerra -néennes,Series A, no. 105, pp. 81-88.

Gordo J., Mutke S. and Gil L., 2013.La relevancia de la especie de patrón portainjerto para el desarrollo de la copa y la producción de piña del pino piñonero injertado. 6º Congreso Forestal Español ‘Montes: Ser-vicios y Desarrollo Rural’, Vitoria-Gasteiz, 10-14 junio-2013 [in Spanish].

Guadaño C. and Mutke, S. (coord.) 2016.Establecimiento de plantaciones clonales de Pinus pinea para la producción de piñón mediterráneo, Monografías INIA: Serie Forestal, Nº 28. INIA, Madrid: 79 p. ISBN 978-84-7498-565-8 [in Spanish].

Loewe-Muñoz V., Balzarini, M., Delard Rodríguez C., Álvarez Contreras A. and Navarro-Cerrillo R.M., 2016. Growth of Stone pine (Pinus pineaL.) European provenances in central Chile, iForest – Biogeosciences and Forestry, 991: e1-e6.

Mutke S., Calama R., González-Martínez S.C., Montero G., Gordo J., Bono D. and Gil L., 2012.Mediterra -nean Stone Pine: Botany and Horticulture. In: Janick J. (ed.): Horticultural Reviews39, John Wiley & Sons, Inc., Hoboken, New Jersey: 153-201. ISBN: 978-1-1180-9678-9.

Ne’eman G. and Trabaud L., (eds), 2000.Ecology, biogeography and management of Pinus halepensisand P. brutiaforest ecosystems in the Mediterranean basin. Backhuys, Leiden, 407 p. ISBN 90-5782-055-2.

Piqué M., Ammari Y., Solano D., Aletà N., Bono D., Sghaier T., Garchi S., Coello J., Coll L. and Mutke S., 2013.Production and management of stone pine (Pinus pinea) for early nut production: grafted plantations as an alternative for restoring degraded areas and generating income in rural communities of Tunisia. In:

Options Méditerranéennes,Series A, no. 105, pp. 43-48.

Prada M.A., Gordo J., De Miguel J., Mutke S., Catalan G., Iglesias S. and Gil L., 1997. Las regiones de pro -cedencia de Pinus pineaL. en España [Stone pine provenance regions in Spain], OAPN-MAPA, Madrid, 130 p. ISBN 978-84-7498-565-8 [in Spanish].

Sghaier T., Palahi M., Garchi S., Bonet J.A., Ammari Y. and Piqué M., 2012.Modeling dominant height growth in planted Pinus pineastands in Northwest of Tunisia. In: International Journal of Forestry Research, 2012, pp. 1687-9368.

Session 2

Models

Which models are needed for