Species Spotlight: Quercus infectoria subsp. veneris (A. Kern.) Meikle

Boissier oak was originally named Quercus boissieri Reut. and later Quercus boissieri var. latifolia (Boiss.) Zohary, but the current accepted name is Q. infectoria subsp. veneris (A. Kern.) Meikle. It is also commonly known as gall oak, dyer’s oak, and Aleppo oak. The tree is present in the Levant countries (Lebanon, Syria, Israel, Palestine, and Jordan), Cyprus, Turkey, northern Iraq, western Iran, and Armenia (Menitsky 2005).

The subspecies Q. infectoria subsp. veneris is different from the subspecies Q. infectoria subsp. infectoria that is present in western parts of Turkey and tends to be a shrubby tree without reaching tree height (Davis 1982). Mouterde (1966) mentions the presence of two varieties in Lebanon, including Q. infectoria var. latifolia, of which Q. boissieri var. latifolia is a homotypic synonym, and another variety that Mouterde didn’t name but suspected to be exclusively found in Lebanon; this variety has not been studied and requires further investigation.

The tree belongs to the White Oaks (Section Quercus), is of a medium size, and can reach more than 16 m in fertile stands. It is characterized by long pointed acorns that are barely covered at their base by an appressed cupule (Figure 1). The leaves are oblong to elliptical, 5–7 cm long and 2.5–4 cm wide (Stephan et al. 2018). The lower blade surface is bluish or greyish green, brighter than the upper blade. The nerves are embossed. Leaves are crenelated, and sometimes lobed (Figures 2 and 3), with these variants eventually attributed to the varieties mentioned by Mouterde.

From a genetic perspective, Boissier oak can easily hybridize with other White Oak species present within its area of distribution. However, a recent molecular study suggested its possible hybridization with oaks from the Cerris group, namely Q. infectoria × cerris (Douaihy et al. 2020, Stephan et al. 2018). However, these peculiar hybrids require in-depth investigations.

The species is an East Mediterranean element but extends to the Irano-Turanian floristic region. It is a marcescent oak, meaning that the leaves may persist on the tree in winter after they turn brown (Figure 4). This trait is a characteristic of sub-Mediterranean species (Vila-Viçosa et al. 2020). Boissier oak thrives in a wide range of bioclimatic zones with winter temperatures ranging from temperate to very cold and with a rainfall regime varying from the semi-arid to the very humid bioclimatic zones. This explains its wide presence from almost 150 m altitude to reach almost the tree line at 1,850 m altitude in Lebanon (Stephan et al. 2020). In this country, the species is widely present on the western and eastern slopes of Mount Lebanon and Mount Hermon (Figure 5 and 6). Elsewhere the species makes shy presence or is rarely dominant. The species has no preferences for soil texture, but prefers deep mature soil, and gentle slopes; otherwise it is dominated by other species such as Q. calliprinos or, in Cyprus, Q. alnifolia. In more arid or cooler environments, it is dominated by other oaks such as Q. brantii or Q. libani in the Zagros Mountains, Kurdistan, or southeastern Anatolia. In mesic conditions it is replaced by Q. cerris. The species can thrive in mixed forests with pines and sometimes with junipers. Accompanying species may include other oaks (Q. look, Q. ithaburensis, Q. petraea subsp. pinnatiloba), Acer spp., Cercis siliquastrum, or members of the Rosaceae family (Abi-Saleh et al. 1976, Ghazanfar & McDaniel 2016, Stephan et al. 2016, Zohary 1973).

The tree is mostly exploited for fuel wood, and to a lesser extent for charcoal production. Some trees are monumental, and therefore widely planted in the past for ornamental purpose. Others are next to religious sites, which increases their cultural value. The fruit is seldom consumed by locals, as a substitute to chestnut. In the past, nutgalls (Gallae officinorum) produced by a parasite insect (Cynips gallae tinctoriae) were used for the extraction of tannins and used for dye as well as for medicinal purpose (Arnaud 2015). Honeydew on leaves is a major source for honeybees.¹

References

Abi-Saleh, B., M. Barbero, I. Nahal, and P. Quezel. 1976. Les séries forestières de végétation au Liban Essai d’interprétation schématique. Bulletin de la Société Botanique de France, 123(9), 541–560. https://doi.org/10.1080/00378941.1976.10835710 

Davis, P.H. (ed.) 1982. Flora of Turkey and the East Aegean Islands 7: 1–947. Edinburgh University Press, Edinburgh.

Ghazanfar, S. A. and T. McDaniel. 2016. Floras of The Middle East: A Quantitative Analysis And Biogeography Of The Flora Of Iraq. Edinburgh Journal of Botany, 73(1), 1–24.

Menitsky Y. Oaks of Asia. 2005. Science Publishers, Enflied.

Mouterde P. 1966. Nouvelle flore du Liban et de la Syrie. Tome seconde. Imprimerie Catholique, Beyrouth.

Arnaud, P. 2015. Théophile-Jules Pelouze (1807-1867). Un Pharmacien Pionnier De La Chimie Organique. Revue D'histoire De La Pharmacie, vol. 102, no. 385: 79–100., https://doi.org/10.3406/pharm.2015.22907.

Stephan, J., C. Bercachy, J. Bechara, E. Charbel and J. López-Tirado. 2020. Local ecological niche modelling to provide suitability maps for 27 forest tree species in edge conditions. IForest - Biogeosciences and Forestry, 13(1), 230–237.

Stephan J., L. Chayban and F. Vessella. 2016. Abiotic factors affecting oaks distribution in Lebanon. Turkish Journal of Botany, 40: 595-609. DOI:10.3906/bot-1601-24

Stephan, J.M., P.W. Teeny, F. Vessella, and B. Schirone. 2018. Oak morphological traits: Between taxa and environmental variability. Flora, 243, 32–44.

Vila-Viçosa, C., J. Gonçalves, J. Honrado, Â. Lomba, R.S. Almeida, F.M. Vázquez, and C. Garcia. 2020. Late Quaternary range shifts of marcescent oaks unveil the dynamics of a major biogeographic transition in southern Europe. Scientific Reports, 10(1), 21598.

Zohary M. 1966. Flora Palaestina, Vol. 1. The Israel Academy of Sciences and Humanities, Goldberg’s Press, Jerusalem.

Zohary, M. 1973. Geobotanical foundations of the Middle East (Vol. 1). Gustav Fischer Verlag.

All photos © Jean Stephan

¹ Honeydew is a sweet substance secreted by aphids which suck the leaf sap; bees harvest it and use it to produce a type of honey known as honeydew honey.