Cedar of "La Francesa", in the region of Béjar (Salamanca). It is undoubtedly one of the most imposing Atlas cedars in the Iberian Peninsula, in a region where this species was probably still present in the Holocene.
The quaternary glaciations were a real catastrophe for the continent's biodiversity, and its tree flora greatly impoverished during this period. The cedars, so common today in our parks and gardens, belong to a genus that was one of the last to disappear from the continental zone of the European continent. A single species, relictual, was able to survive on the island of Cyprus (Cedrus brevifolia), being this species the last representative of this type in Europe.
Origin and expansión
Confined now to the mountains of North Africa, southern Turkey, the Middle East and the Himalayas, the origin of this genus is found in East Asia, as shown by phylogenetic studies (1) and fossil evidence. From there, it expanded to the west, differentiating firstly the Himalayan cedar. After colonizing the whole south of the European continent, an eastern population was differentiated from which the cedar of Lebanon and the cedar of Cyprus would be born and a western population reaching North Africa through the Iberian Peninsula when the Strait of Gibraltar was closed in the Yonger Miocene (Messinian).
It is interesting to note that the differentiation of cedar, a result of the isolation of different populations, does not prevent the crossing of different species, which often makes it difficult to identify the individuals planted in our parks, which may be the result of the crossing of several of these species . This process of differentiation seems to be quite old in any case, prior to the glaciations. At the end of the Pliocene, the cedar (sensu lato) was present in all reliefs from the south of the continent, from the Iberian Peninsula to the Caucasus.
Regression and possible refuges
Cedar was already at the end of the tertiary, an average elevation tree that coexisted in many places now missing with conifers as Tsuga and Cathaya. These species took refuge during the glaciations, in the peninsulas of the south of the European continent. Its presence is commonly accepted in the Italic Peninsula and in the north of the Iberian Peninsula until the Middle Pleistocene. The presence of cedar pollen in more recent sediments is generally attributed, however, to wind transport from North Africa. The detailed study of some recent pollen diagrams suggests, however, that cedar could be present in the Peninsula until much later dates.
Pollen diagram of deposit of Cuerpo de Hombre (Sierra de Gredos). Notice in particular the simultaneous decline of the pine and the cedar at the moment when man arises.
A recent study in postglacial sediments of the Sierra de Gredos [2] reveals the more or less continuous presence of cedar in one of the analyzed profiles, which is hardly explained by a contribution from the North African wind. The pollen diagram of this profile (Cuerpo de Hombre) shows that the emergence of cedar always coincides with periods when the tree cover reaches a maximum, as reflected by the pine curve. The disappearance of the cedar, on the other hand, coincides with the disappearance of the pine at the time when the forests of this region were overthrown and that these lands completely changed of use. A more random presence of cedar would have been more compatible with wind transportation. The most convincing argument in favor of a local origin of this pollen, however, is its total absence in the other profiles studied in this same region. It seems very improbable that after a journey of several hundred kilometers, the cedar pollen appears "concentrated" in a single profile. Anyone who has experienced an episode of "desert dust" knows perfectly well that when this happens, the desert sand covers vast expanses indiscriminately.
A ski resort in the Pyrenees on a desert dust day last April (2018) / Photography: https://twitter.com/hashtag/lluviadebarro
A very similar situation is observed in other regions. In Andalusia, for example, cedar pollen appears in significant quantities in sediments at the Bajondillo grotto (Torremolinos), where it has a continuous presence in the pollen diagram until the end of the last glacial period, coinciding with the emergence of the Aleppo pine [3]. Here again, it seems that it is not the result of mere coincidence. But in the same way is the total absence of the cedar in the sediments of the same time in the cave of Gorham (Gibraltar), only to 60 km more to the west, what is more remarkable in the context of a contribution by the wind. It should be noted that the cedar itself is present in this same deposit in older sediments (Upper Pleistocene).
Pollen diagram of the cave del Bajondillo (Torremolinos). Note the simultaneous development of Abies, Betula and Cedrus at the end of the last ice age.
This heterogeneity of cedar presence in Upper Pleistocene and Holocene sediments is explained much more easily by the presence of small Cedar populations in the Iberian Peninsula. Its disappearance, as shown by the Sierra de Gredos example, would have been very recent and the man apparently has a clear responsibility because the species has not survived to this day. This will only be definitively demonstrated on the day that Holocene macrorrests are found attributable to this species. For now it is only a suspect, but the evidence clearly indicates that it would be present. For now, as far as I know, no one has explained the absence of the cedar in all places near and contemporaneous with those in which its presence was revealed.
| Cedrus | Familia: Pinaceae | Orden: Pinales | |
Trees evergreen, monoecious; branchlets strongly dimorphic: long branchlets growing several cm each year and bearing very slow-growing, lateral short branchlets; winter buds small, scales persistent. Leaves spirally arranged and radially spreading on long branchlets, shorter and very densely clustered on short branchlets, needlelike, triangular or ± quadrangular in cross section, stiff, stomatal lines present both adaxially and abaxially, most numerous abaxially, vascular bundles 2, almost fused, resin canals 2, small, marginal. Cones borne on apex of short branchlets, solitary, erect. Pollen cones with many spirally arranged microsporophylls; microsporangia 2; pollen not saccate. Seed cones erect, light purple at fertilization, maturing in 2nd(or 3rd) year; ovulate scales spirally arranged, sessile, with small bracts and 2 ovules adaxially. Seed scales closely arranged, large, woody, those at base and apex of cone sterile, deciduous at maturity. Bracts minute, falling together with seed scales at maturity from persistent, central axis. Seeds with large, membranous wing. Cotyledons usually 6-10. Germination epigeal. 2n = 24. Descripción: eFlorss | |||
A bright future
Climate change represents, for the Atlas cedar, a serious threat and an extraordinary opportunity. Rising temperatures, in fact, have already pushed the lower-lying populations of North Africa to the limit. Illegal logging and overgrazing are also very serious threats in their area of origin and the future of the species in North Africa is very uncertain. Fortunately, French foresters soon realized the potential that this species could have in the Mediterranean region and the species was planted in France practically since it was discovered (by Europeans). The cedar forests of the Luberon and Mont Ventoux today show the extent to which this species is perfectly adapted to the sub-Mediterranean climate which is precisely one of the types of climate that most will see its area extend north to the end of the century, making this species one of the most promising for the future.
Cedar grove in the Petit Lubéron massif (France), where they cover about 207 ha. only in the territory of the small town of Lacoste. The planting of cedars in this massif that was totally "peeled" in the nineteenth century was a resounding success, becoming its cedar forest one of the great attractions of the region. Photography: Tourist Office of Lacoste.e
Paradoxically, this species did not arouse in Spain the same interest as in France and was only planted on a very small scale. (Atlas cedar in the Iberian Peninsula). The current climate must, however, lead our authorities to become more interested in this tree, which was one of the most important species of our mountains before being a victim of glaciations and overexploitation. The quality of its wood, its relative resistance to drought and its low flammability are, in any case, compelling reasons that argue in its favor.
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(1) Qiao C-Y. Et al. (2007) / Phylogeny and Biogeography of Cedrus (Pinaceae) Inferred from Sequences of Seven Paternal Chloroplast and Maternal Mitochondrial DNA Regions / Annals of Botany, Vol. 100. pp. 573–580, | |
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(2) Ruiz-Zapata1 M.B. et al. (2011) / Dinámica de la vegetación durante el Holoceno en la Sierra de Gredos (Sistema Central Español) / Bol. R. Soc. Esp. Hist. Nat. Sec. Geol., Vol. 105 (1-4), pp. 109-123 | |
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(3) López-Sáez JA, López-García P, Cortés Sánchez M. 2007. Paleovegetación del Cuaternario reciente: Estudio arqueopalinológico. En: Cortés Sánchez M. (Ed), Cueva Bajondillo (Torremolinos). Secuencia cronocultural y paleoambiental del Cuaternario reciente en la Bahía de Málaga. Centro de Ediciones de la Dipu- tación de Málaga, Junta de Andalucía, Universidad de Málaga, Fundación Cueva de Nerja y Fundación Obra Social de Unicaja, Málaga, pp 139-156 | |
Author: Adrián Rodríguez
Translation: João Ferro
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