Silvio May
SILVIO MAY is with the Istituto di Sperimentazione per la Pioppicoltura, Italy's poplar research institute located in Rome.
A short trip to Afghanistan to survey the indigenous poplars, both in their natural and cultivated stands, proved extremely interesting to this writer. The aim, in particular, was to establish whether these trees were suitable for breeding programmes.
The country has various species and types of poplars worthy of attention. Quite a few could play an important role in the Mediterranean region, in the mountains as well as in the plains. Some types were quite unknown, unreported so far in any specialized or scientific literature. [Research on their botanical features and their silvicultural aptitudes should be carried out by the experimental institutes working on poplars. This is, indeed, valuable breeding material and its use might help solve some problems of significance in the field of poplar breeding research.
Afghanistan is basically a mountainous country dominated by the Hindu Kush range, which runs across it diagonally. Its continental climate is marked by a wide variety of temperatures due to the altitude more than the latitude, by strong winds and by long periods of drought. Temperatures at Kabul, the capital, which is situated 1800 m above sea-level range from around-20 to-25°C in winter to 40°C in summer. Precipitation is rather scanty, from 200 to 300 mm per year, distributed during the December-April period. The influence of monsoons is hardly felt at this longitude. The soil is in general good where, in small areas of the valleys, irrigation is available. Apart from mountainous zones covered with forests and few cultivated lands, the rest of Afghanistan is formed by pasture lands (on the plateaux), steppes and desert (south and southeast).
Poplars are grown almost everywhere that irrigation is available. The main and most important species or types seen during the trip belong to the sections Leuce and Aigeiros. Though Populus euphratica and P. ciliata (Turanga and Leucoides sections respectively) are also reported to be represented in the country, the first one does not constitute stands with trees of economic importance and those specimens which were shown in cultivation as belonging to the second one (P. ciliata) were found to be P. nigra.
Types of poplars recognized - within the limits of the visit - as being of major interest are analysed below:
Good strains of this hybrid (locally known as "khadang") constitute fine rows along the avenues at Paghman (near Kabul). Characteristic of the type, apart from its rapid growth rate and good ability to root from cuttings, is its fine habit. But success in propagation by cuttings, a quality seldom found in this type, is what makes this strain highly valuable. The supposed clonal state of this strain would get more support if, at the time of the flowering, one sex only were to be found on the trees.
Thickly cultivated poplars are used for roofing and posts
Excellent specimen of Populus nigra growing in Tapa Gardens
Populus alba logs. They will be used in the manufacture of such items as matches and boxes.
Below, right: local white poplar strain of vigorous growth habit (Astalif area)
Roadside plantation of Populus alba at Kariza Mir, once a royal reserve
A strain showing specimens of very fine habit, being slender, semifastigiate, with thin narrow crown and a very straight trunk. cylindrical and undivided up to the top, it is cultivated in stands in the Paghman area. These poplars are perhaps related to the specific group called 'Roumi', cultivated in Syria. They are said to be easily propagated by cuttings. Their rate of growth is fairly slow as compared to P. x canescens but the habit is exceptionally fine, so much so that it would be difficult to find any equivalent among the European strains belonging to this species. Since the trees are very uniform and regular in shape, it is possible that this also is a clonal strain.
Old and very vigorous specimens of P. alba are growing in the Tapa Gardens area as isolated trees. Their habit, in spite of a slightly spreading and full crown, is excellent as compared with similar European specimens. The portion of the trunk below the crown is perfectly cylindrical and the bark there is of an almost chalky white, smooth and most of it without any rhytidoma, which gives an attractive, aesthetic appearance to the trees. They are very interesting indeed both for cultivation and for amenity purposes owing to their rapid rate of growth and to their ornamental features. Female trees are represented, as some fruit catkins were found on the ground, though the seed season had passed at the time of the visit.
Quite a few roadside plantations at Kariza Mir, a large estate which used to be the reserve of the former king of Afghanistan, are constituted by an excellent type of P. alba. Its habit is similar to that of P. alba semifastigiate, though less slender and shorter. The crowns are thicker and spreading perhaps because they are exposed to more light, here in isolated lines, than the stand plantations in the Paghman area. Moreover, if it is a matter of a clonal strain, as it seems to be, this is surely female since a lot of open mature capsules and cotton were still found either on the ground or on the trees. This P. alba type should be useful as an ornamental tree and should be considered. for propagation mainly for this purpose.
A poplar thriving in the Astalif area (about 2100 m above sea level) is surely, for its habit, the world's best representative of the section Leuce. It is difficult to imagine a better physical appearance in a tree to be grown for wood production than the one presented by this poplar. Its outstanding features are: an absolutely lofty, tall, clean, perfectly straight and cylindrical stem, the light, thin and narow crown, the smooth bark of a greysh colour. The wood is of a good quality, ivory white and without any defect, thanks to the perfect habit of the tree.
The Populus canescens Sm. cv. 'bachofeni', growing in the Deliblatska region of Yugoslavia, though inferior, is the only poplar of the Leuce group that can be compared, for external characteristics, to the Astalif poplar, a strain which, both for breeding work and cultivation trials, should be of great interest. Its ability to root by cuttings has to be tried.
While awaiting a correct labelling of the Astalif species by botanists, its superlatively fine habit might suggest a name stating this quality.
There are some intensively irrigated plantations of P. alba on good lands near Kabul. Those visited during the trip were on large enough areas at Darulaman Park, Dedana, Chalstoon and Demurat Khan. They are constituted by populations of P. alba, where more or less sinuous trees stand alongside very straight ones. There is a high variability in their general habit and in the rate of growth and, presumably, in the wood quality. One of the first requirements here is to select clonal material from the best frees and propagate it. Shortage of time did not allow us to do it during the visit.
Two kinds of P. nigra were seen during the tour. The most widely distributed and cultivated throughout the country is the black fastigiate poplar, closely related to the Populus thevestina of the Balkan countries and, perhaps, to the P. nigra cv. 'Hamoui' cultivated in the Near East. It is the most important, economically, of the poplars of Afghanistan. Its cultivation is traditional, and extended on a large scale being grown from remote times. It is a very familiar tree, so far cultivated thickly under the old traditional methods. The villagers get earlier returns by using the trees mainly for thatching roofs and as posts.
The second one is perhaps more interesting from a breeding point of view, because it seems to be a population and therefore with a greater chance of success in a possible work of hybridization. The best specimens of this type were found at Tapa Gardens. Their habit, which has nothing of the fastigiate form, is good and the rate of growth faster. These poplars are also in some places cultivated and indicated erroneously as P. ciliata.
Different types of willows worthy of attention were seen everywhere during the trip. It was not possible to group them under specific names, due to the very marked heteromorphism in their botanical features.
The pending identification problems, however, will not affect a possible clonal selection from some "plus trees" of the different strains. It is advisable that, along with poplars, these willow strains also be considered as promising for breeding programmes.
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