In previous articles, we discovered the thermophilic species that disappeared from the European continent and referred to the existence of different glacial refuges in the south and periphery of the European continent, where a whole series of species that were still present in Europe at the end of the Tertiary era and in the Lower Pleistocene (Quaternary) survived. Unfortunately, not all the species present in Europe at that time had the chance to reach these refuge areas. Many of them disappeared permanently and their close relatives now live in Asia and/or North America. However, a number of these species had a practically holartic or Eurasian distribution area and were fortunate enough to survive outside the European continent. The most famous example is probably the gingko, extremely rare in nature and perhaps saved from possible extinction by the veneration that the Eastern populations professed for this tree.
Less known than ginkgo, but also originally from China, the gutta-percha tree (Eucommia ulmoides) shares a very similar destiny with ginkgo. That species is also, in effect, the only representative of a monotypic family and genus. Like ginkgo, the species is cultivated since time immemorial and its exact origin (natural populations) has not been clearly established. It is a tree with numerous medicinal properties that also has a unique feature among the trees of the cold temperate zones: it secretes latex.
This feature attracted the attention of Westerners at the beginning of the 20th century, who saw in it a possible alternative to rubber of tropical origin. That led to different attempts at acclimatization that were more or less successful. Most of them were soon abandoned when synthetic rubber production developed and it was very difficult to grow this species, from which only male feet were initially obtained. The only country that took the experiment to an advanced stage (production) was the USSR in the 1930s. Some of these experimental plantations still exist (see video below). In other countries, this species is very rare, being able to see only in arboretums and botanical gardens.
Ecology
The gutta-percha tree is capable of living in a wide range of ecological conditions and can be observed in such disparate environments as mixed forests, cleared forests, small forests, low mountains, ridges, valleys, dry ravines and fields (Flora of China). In China, this species has become very rare in the wild and appears dispersed in a relatively large area (see map). Widely cultivated, it has been naturalized in a multitude of places.
Distribution map of Eucommia ulmoides (left) and annual precipitation map of eastern China (right).
As the previous map shows, the species is capable of living in relatively dry areas where rainfall is barely more than 400 mm. One of the most important factors for this species are spring temperatures, Eucommia ulmoides seeds need to germinate at springtime temperatures (April) between 13 and 22 degrees, with the optimal temperature of 18 ° C for germination [1].
Past distribution
The fossils of Eucommia that have been found in Europe in the sediments of the late Pliocene or Quaternary are so similar to the current species that these have usually been attributed to that species. It is likely that other species of this genus were present in earlier times but the current was the only one that managed to reach our days. It managed to survive in southern Europe until the middle Pleistocene and, like many other species that disappeared at that time, it does not seem to have been very good for the intensification and lengthening of the glacial periods in the Upper Pleistocene. It was in the Pliocene and at the beginning of the Pleistocene, a frequent and abundant species in much of Europe and the Iberian Peninsula, where it coexisted with numerous species of deciduous and persistent trees. Given the ecological breadth of this species, it is very likely that it was present in our country in a wide range of ecosystems, both in the Mediterranean and Eurosiberian regions.
The variety of environments in which this species is able to live makes it difficult to know in which types of environments it lived in southern Europe, as the species was probably present at that time in both the Mediterranean and Euro-Siberian regions.
| Eucommia | Family: Eucommiaceae | Order: Garryales | |
Trees deciduous, dioecious. Sapwood and bark containing latex. Buds ovoid; scales deciduous. Leaves alternate, spirally arranged, exstipulate, petiolate; leaf blade simple, usually elliptic, sometimes somewhat ovate, obovate, or oblong, containing latex (forming strands if blade is transversely broken and pulled apart), pinnately veined, base rounded or cuneate-rounded, margin densely serrate with gland-tipped teeth, apex abruptly narrowed into an acuminate tip. Flowers axillary, borne near base of current year’s branchlets, very shortly pedicellate, without perianth, wind pollinated. Male flowers clustered; stamens 5–12, linear; filaments very short; anthers basifixed, 4-locular, dehiscing by longitudinal slits; connective slightly prolonged. Female flowers solitary: ovary stipitate, composed of 2 connate carpels, 1-locular, elongate, compressed, glabrous, apex 2-lobed; stigmas 2, decurrent, reflexed-spreading; ovules 2, collateral, anatropous, 1 aborting. Fruit an indehiscent samara, long elliptic to narrowly oblong, compressed, winged around margin; wing gradually narrowed at base into stipe, shortly 2-lobed at apex with sinus stigmatic; pericarp thinly leathery. Seed 1, linear, compressed, rounded at both ends; testa membranous; endosperm copious; embryo erect, large; cotyledons compressed, fleshy. Source: Flora of China | |||
It is a species rarely cultivated in our country. There are, as far as I know, two individulas in the Royal Botanical Garden of Madrid (one of them already quite grown up), another one in Barcelona and ... little else. I have not found, in any case, any reference to other specimens in other regions. It is curious, in any case, that this species has not awakened until now the curiosity of our forestry engineers. Of course nobody was aware until recently that this species was so frequent in our forests at that time. We'll see if the little Eucommias I've planted in my neighborhood go ahead. I have planted them in a small area of my neighborhood in which both the exposure and the edaphic conditions vary a lot, with the idea of seeing if that species is able to naturalize in the Mediterranean region, in places where conditions are somewhat more favorable. If the rabbits do not annihilate them and if nobody steals all the protectors that I have put, then maybe I'll tell you good news a few years from now.
Eucommia ulmoides leaf seen against the light. Real Jardín Botánico de Madrid.
Next year, I will try to plant some of them in an area with a more favourable climate (sub-Mediterranean). Elsewhere, as the short video shot in southern Russia (Sochi region) clearly shows, there is no doubt in my mind that this species is capable of growing almost anywhere. If you are aware of his presence in the area where you live, feel free to leave your testimony in the comments in this article.
One of the small 1-year-old percha-gutta trees I planted in my neighbourhood.
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(1) Wang Y.-F. et al. (2003) / Eucommia (Eucommiaceae), a potential biothermometer for the reconstruction of paleoenvironments / American Journal of Botany, Vol. 90(1), pp. 1–7. | |
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