Poplar

Origins

The paleobotanists agree to give to the poplars an extremely old origin, among Angiospermes. Switzerland O. Heer allots to the populus kind certain prints of simple sheets met in Néocomien de Kome, on the west coast of Greenland (P. primaeva Heer).

In Cénomanien d' Athané, Dicotylédones become numerous and the populus kind is well represented there beside the ferns, of cycadées, the Quercus, Ficus, Laurus, Magnolia, Rhamnus, Myrica, etc but only with sheets pointing out those of the section of the Turanga.

Turanga would be thus primitive forms. It seems that it is only with the Sénonien that the representatives of the other sections appeared.

Wood

It is a Bois white, light, tender, rather resistant, adhering and not very fissile. It is easy with Colle R, to tint, to paint, Clou er and Agrafe R but it Scie and pounce with difficulty.

The poplars are cultivated in an industrial way by “populiculteurs” in dedicated zones known as Peupleraie S. The beautiful balls are used for the unwinding. One makes panels of them (lathed, Contreplaqué S), boxes with Fromage, Emballage S light for Fruit S and Légume S, baskets of Huître S or Allumette S. the second quality is generally made profitable for the manufacture of pallet S or pastes with Papier.

Principal species

The kind Populus is divided into six sections:

the section Turanga : Populus euphratica Oliv., P. pruinosa Schrenk, P. ilicifolia (Engler) Roller
the section Leuce :

the sub-section Trepidae (tremble): the Trembles ( Populus trembled L.), P. adenopoda Maximowicz, P.davidiana Dode, P. gamblei Dode, P. glandulosa Uyeki, P. grandidentata Michx, P. guzmanantlensis R.Vasquez & Cuevas, P. monticola Brandegee, P. ningshanica C. Wang and S.L. Tung, P. rotundifolia Griffith, P. sieboldii Miquel, P. simaroa Rzed, P. tremuloïdes Michx, P. wulianensis S.B. Liang and X.W. Li.
the sub-section Albidae (white poplars): the white Poplar ( Populus alba L.)

the section Aigeiros (black poplars): a European species the black Poplar ( Populus will nigra L.), several North-American species: Populus deltoides (Bartr.) Marsh. (several subspecies: P. deltoides subsp. deltoides, P. deltoides subsp. will monilifera and P. deltoides subsp. wislizeni);
the section Tacamahaca (poplars balsam trees): Populus trichocarpa , P. amurensis Komarov, P. angustifolia James, P. will balsamifera Mill., P. ciliata Wallich Royle ex, P. girinensis Skvortov, P. haoana W.C. Chen and C.Wang, P. hsinganica C. Wang & Skvortzov, P. Laurifolia Ledebour, P. hyrcana Grossh, P. intramongolica T.Y. Sun & E.W. My, P. kangdingensis C. Wang & S.L. Tung, P. keerqinensis T.Y. Sun, P. nakaii Skvortzov, P. pamirica Komarov, P. platyplylla T.Y. Sun, P. pseudomaximowiczii C. Wang & S.L. Tung, P. pseudosimonii Kitagawa, P. purdomii Rehder, P. qamdoensis C. Wang & S.L. Tung, P. schneideri (Rehder) NR. Chao, P. simonii Career, P. suaveolens Fisch, P. szechuanica C.K. Schneider, P. trinervis C. Wang & S.L. Tung, P. wenxianica Z.C. Feng and J.L. Guo, P. wuana C. Wang & S.L. Tung, P. yatungensis C. Wang & S.L. Tung, P. yuana C. Wang & S.L. Tung, P. yunnanensis Dode.
the section Leucoides : P. heterophylla L., P. lasiocarpa Olivier, P. pseudoglauca C. Wang & S.L. Tung, P. wilsonii C.K. Schneider.
the section Abaso : represented by only one species the Populus mexicana Wesm. ex cd., 1868

The natural species were used to create cultivars since the 18th century. Certain hybrids were fixed at the wild state. The principal species of poplars are found:

Populus will nigra - the black Peuplier (Asia and Europe)

Populus will nigra L. VAr. italica Mœnch - the Poplar of Italy or Lombardy
Populus will nigra napolitana - the Peuplier of Naples
Blanc of the Garonne - cultivar created starting from local populations
Vert of the Garonne - cultivar created starting from local populations

Populus alba L. - the white Peuplier
Populus trichocarpa Torr. & Gray ex Hook. - the Poplar balsam tree
Populus deltoides (Bartr.) Marsh. - the Poplar deltoïde
Populus simonii - the Peuplier of Simon
Populus trembled L. - the Tremble
Populus yunnannensis - the Peuplier of Yunnan
Populus canescens (Has.) Sm. - the Poplar grisard (undoubtedly a natural hybrid of P. alba and P. trembled )
Populus × canadensis Mœnch - the hybrid Peuplier euraméricain (hybrid of female P. deltoides and P. will nigra male)
the inter-American hybrid poplars - together of hybrids of P. trichocarpa and P. deltoides
Populus lasiocarpa Oliv., 1890 - Peuplier of China

Genetic sequencing

The poplar ( Populus trichocarpa ) was the first tree whose Génome was entirely sequence. It was selected for its “small” genome which contains 485 million pairs of bases (the genome of the pine contains 40 to 50 times of them more) distributed on 38 Chromosome S. the other selection criterion was the capacity of this tree to grow of 5 m per annum, making it possible to evaluate the genetic modifications effectively. Approximately 45.500 Gène S coding of the Protéine S were identified.

Disease

Many clones were shown particularly sensitive to rusts and certain insects defoliator, which systematically seem to adapt after a few years to the clones selected to resist to them.

Ecology and sylviculture of the poplars

natural settlements

The differences between the species of poplar are as important as there are similarities in the management of their natural settlements. In the hot and dry areas or the areas close to the Arctic Circle, the poplar plantations are confined with the easily flooded plains and the edges of river where they generally constitute almost pure settlements on several kilometers. In the northern forests and moderated, the poplars are commonly met either in pure trainings or in mixed settlements. Sylviculture applied is based firstly on the modes of regeneration privileged by such or such group of poplars. Thus the sylviculture of tremble will base itself in particular on their high capacities to sucker whereas the management of the poplars of the arid zones ( P. euphratica , P. fremontii ,…) will base itself preferentially on the sexuée reproduction.

vegetative regeneration

This way of natural reproduction was privileged by tremble (drageonnement). It led to the creation of monoclonal settlements and this without any intervention of the man. The evolution of a tree resulting from sowing towards a monoclonal settlement takes tens of centuries. In the area of the Big lakes and Alaska, the intermediate size of these monoclonal settlements varies from 2 to 8 ares what very weak is compared with the settlements of the Rocky Mountains. In the south of Utah, a natural settlement monoclonal covers 43 ha, which probably makes of it the greatest living organism of the world. It is composed of 47000 stems and weighs, according to the estimates, 6000 tons (Grant and Al 1992).

In the past, the regeneration of tremble was mainly conditioned by the Incendie S whereas the regeneration of the other groups (white poplars, balsam trees, blacks,….) was especially conditioned by the disturbances of the aggradation, rivers (erosions, flood,….) or migrations of large mammals which broke and buried branches by supporting the propagation by cutting. The settlements of tremble are usually exploited in Coupe with white . Tests of progressive cuts caused less good drageonnement and a weaker growth of the growths, the presence of a however diffuse raised stage pretense to disadvantage the massive and fast regeneration of these poplars. The performance of drageonnement is also conditioned by the temperature of the ground, of the reserves in carbohydrates of the system racinaire, the genotype, the presence of depredaters (large herbivores, insects,…), of the conditions of harvest and many other parameters (Maini 1967; Zasada and Schier 1973; Shepperd and Fairweather, 1994). The forestry development must be particularly respectful ground if one wants to make sure of a good drageonnement. Phenomena of compaction and wounds of the apparatus racinaire (supporting the diffusion of the Armillaire) and decreasing by as much the capacities of the settlement to regenerate itself (Navratil and Al 1996). In the sites where regeneration is optimal, one counts from 30.000 to 100.000 suckers by Hectare.
Although less prolific than tremble them, the P. will balsamifera also has a proportion to sucker. For example in the Western northern forests of Canada one counts 3000 stems/hectare after exploitation (Navratil and Bella, 1990). The P. will balsamifera account also of other strategies of vegetative regeneration (propagation by cutting, rejection of stock,…).
D' other poplars also sucker but reproduce by other methods of vegetative regeneration; rejections of stocks, propagation by cutting or Décurtation (much rarer). For these species, vegetative regeneration is privileged under the less favorable stationelles conditions.

sexuée regeneration

Less important in the development of the sylviculture of the aspen plantations except valley, it is on the other hand essential for the forest systems ripuaires. The lifespan of seed being very short (less than two to three weeks), it is imperative that the period of sowing coincides with the end of the floods. The success of sowing is conditioned by a wet bed of sowing, completely deprived of other plants and quite sunny. These conditions are generally met on the strikes, alluvial deposits and terraces either eroded by the risings, or lately created by the alluvial deposits. Simultaneity between the end of raw and the period of sowing of the poplars is the fruit long years of evolution. The interventions on the rivers like their diversion, the bank stabilization, the creation of stopping, pumpings, decrease to see make impossible natural regeneration. Although the seeds can move on several kilometers grace in particular to the currents of convection (or in the event of high winds), most of the time they hardly settle to a hundred meters of their génitrices.

the sylviculture of tremble

The rules of management of tremble are relatively simple. Tremble were called by Graham and Al (1963) the trees phoenix and this for a good reason because they can in one to two years after disturbance of their medium (exploitation, storm, fire,…) to reconquer and dominate the site. Sylviculture most commonly applied is based on natural regeneration by drageonnement and is followed of no other treatment until the exploitation. strong competition between the seedlings ensures a fast selection in the settlement. Falls of growth or other effects related to the density would have only few impacts on the voluminal production; in fact the dense settlements are less likely to be affected by the attacks of insects and the diseases. The exploitation with white étoc continues to be the operating system dominating (in particular over the continent North-American). This known as, lesexigences of durable management of the forest implied the practice of certain alternatives. For example in Alberta, on the cut, Alberta Pacific Corporation leaves on foot + 5% of volume to be exploited so to meet the objectives of the nature conservation (Stelfox 1995). Always in Alberta, in the management of the mixed settlements tremble - coniferous, the poplars are exploited in first in order to allow the maintenance of conifers. The goal is not for as much not the elimination of tremble but well the maintenance of the mixed forest. In the north of the Big lakes, the forest Administration directs its management to support the conversion of certain poplar plantations towards forest systems with longévives species (according to the same principles as the conversion of the coppice into grove applied into Europe). The maintenance of trees on the setting with white strongly decreases the strength and the growth of the suckers. Perala (1977) indicated that 2,4 to 3,6 m2/ha of stems on foot on the cut reduced the growth of the suckers from 35 to 40%. On the other hand Doucet (1989) quoted examples of piece drageonnement having a good in spite of the conservation of 14 m2/ha trees on foot. Another study of National Superior Forest off Minnesota carried out by Stone and Al (2000) indicated that a reserve of 75 arbres/ha uniformly distributed decreased drageonnement by 33 to 41% but without to affect the growth of those. In practice, the left trees either are distributed uniformly on the piece, or concentrated in small groups from 10 to 30 trees. The size recommended of surfaces of exploitation per setting to white is about 4-5 ha and those must be ideally dispersed in old settlements. In the good sites (index stationnel of 24,5m at 50 years), the exploitations have a rotation from 25 to 30 years with a surface terrière of 25 with 30m2/ha (Perala 1977).

the sylviculture of the other types of poplars

For the other poplars, the conditions of operating can be similar but many natural poplar plantations are often replaced by plantations. In the forest formations related to the rivers to strong disturbances, the poplars are among the first colonizers with the willows and the alders. According to the cases, these forest formations can evolve to settlements dominated by longévives gasolines. The sylviculture of natural settlements can present several scénarii adapted to the types of settlements (mixed or pure) and to the awaited objectives (evolution towards another forest facies or perpetuation of the poplar plantation). In these poplar plantations, the breaks, when that proves to be possible, are practiced very early and frequently. Generally the exploitation of the poplars is carried out by the method of the settings with white which allows then regeneration with the same species. This method is however contra-indicated for certain species ( P. euphratica , P. pruinosa ,…) occupying the arid zones because it weakens the settlement and mortgages natural regeneration. In these types of settlements, one will choose exploitations of trees isolated or by groups from some trees (4-5) in order to preserve a protective forest state while ensuring the rejections or sowings of the sufficient conditions of development. When the young seedlings exceeded the critical stage, one can increase the “cones” of regeneration. This known as, natural regenerations are primarily centered on the colonization of new sites via sowing and less by regeneration on same site even if the latter is frequent for the species suckering easily.

Sylviculture of the plantations of poplars

The culture of poplar rests on three essential pillars: the quality of the cultivar used, quality of the station and the treatments applied to the culture.

Seedbeds

One of the great advantages of the poplars is that the material of higher quality can be quickly available into large quantity. It is all the more true for the poplars of the sections Aigeros and Tacamahaca whose propagation by cutting is relatively easy. The multiplication at tremble is a little more difficult because it requires cuttings with heel racinaire called barbatelles. The products of the seedbed can be rather different according to the mode from propagation, the costs, the type of plantation considered, the conditions of plantation,… the not marbled cuttings are produced starting from one year old wood and vary according to the modes of production of the mini propagation by cutting (2-3 cm) to the more traditional propagation by cutting (15cm with maximum 100 cm). Within the framework of an intensive production with densities of plantation higher than 700 tiges/ha, one will employ traditional cuttings preferentially. This type of plantation requires a tillage comparable with a traditional agricultural culture and requires a control of the so meticulous adventitious vegetation. For less dense plantations (< 400 tiges/ha), one will prefer the use of plank timbers; the length of those can vary between 1,5 m and 5 or 6 Mr. This type of material allows replantings in more difficult mediums (such as in forests) and controls it adventitious vegetation becoming less crucial. These plank timbers are produced starting from the traditional cuttings, installed with + great density according to the climatic conditions (temperature, sunning,…) and gauges it cuttings desired. Thus, in the plain of the Mississippi, the spacings are typically of 0,3m X 0,3m is slightly less 0,1m2/plant; the plank timbers are produced into 1 or 2 years and under these conditions, the irrigation is frequent. These strong densities are practiced in order to prevent the development of side branches what makes it possible to strongly reduce the preparing of the seedlings; this practice functions particularly well with the P. deltoïdes and P.X euramericana but less with the less heliophilous hybrids such as P. trichocarpa X P. deltoïdes or P. trichocarpa X P. will nigra . Another example, in Belgium, the practiced density is from 5000 to 10000 seedlings/ha is spacings of 1m X 2m to 1m X 1m. Classically, the plank timbers are produced in 2-3 years according to the cultivars; the irrigation is rare there but the production requires an important labor for the preparing of the seedlings. The seedlings of tremble can be transplanted with to start from barbatelles one year is with the size of a one year sowing (60 to 100 cm). The production of seedlings out of container is more anecdotic. It can be realized either starting from sowing, of mini cuttings, cuttings `in green' or cuttings of root (trembles). It is almost not used in Europe and is common for plantations in arid mediums.

The competition between the poplar and the adventitious vegetation is important and it is of as much more necessary to reduce it than the seedlings installed are small. Several methods can to be considered:

• Mechanical method: in the pieces planted densément, a tillage is necessary. Practiced well it makes it possible to reduce in an important way the adventitious vegetation. When the spacing allows it, it is still possible to weed mechanically between the lines. • Chemical method: an arsenal of weedkillers already employed in agriculture exists and is well-known. The most used of the two with dimensions ones of the Atlantic are containing glyphosate. The treatments are particularly necessary during the first years in the plantations to strong densities or the sites for strong herbaceous pressure like the plantations in meadow. • Method of the mulching: more natural, it allows the control of the vegetation for a certain period but afterwards, this one reappears; its employment makes it possible to improve the hydrous economy but also creates a shelter for the rodents. • Method of plastic film: it is an alternative of the mulching, the cover is ensured by a plastic film. This technique is in particular practiced in certain areas of Europe in order to optimize the hydrous reserve of the ground and to limit the use of phytocides.

In seedbed, the essential problems are related to the diseases such as rusts, the Marssonina sp. and deteriorations of growths. The latter being supported by strong attacks of the first two diseases, it is on those that will concentrate the efforts of the nursery gardener.

The foliar diseases and in particular rusts will be the subject of suitable treatments (use of the fungicides approved depending on the states). Deteriorations of the growths are caused by many different agents like Discosporium populeum , Cytospora chrysosperma , Phomopsis oblonga ,…

The most awkward depredaters in seedbed are the défoliateurs like the chrysomèles and the altises (in particular Chrysomela scripta in the USA) and the insects xylophagous such as the sésies and the saperdes. Here also of adapted insecticides exist and can be used according to the national legislations.

Plantations

The ideal ground is aired, rich, fed well well in water and sufficiently deep (depth of the tablecloth to more than one meter). It has a muddy texture + light with a pH water ranging between 5 and 7,5 (Baker and Broadfoot 1979). But in fact, each species and hybrid of poplars have its own requirements or its tolerances (the P. trembled will support best the acid grounds, the P. heterophylla the mouilleuses stations, the P. euphratica the halomorphic grounds,…). The distances from plantations depend on the species concerned and the product considered. Within the framework of a production of sawlog of high-quality and without break, the plantations are carried out with very weak density (between 300 and 100 seedlings/ha) like that is practiced in particular in Europe. In the southernmost zones this type of culture can be associated with agricultural speculations such as the production with corn, beet, market-gardening products, of soya,… More important densities are practiced in particular in the USA, with spacings varying of 1600 to 625 stems/ha. Without breaks, the product of these plantations will feed the industry of cellulose or the panels (e.g. OSB). In other areas like China, where the strong densities are regularly used, the wood of breaks are useful in particular like glazing bar of construction, wood for the handles of tools or like fuel. The practiced densities also depend on the species or the hybrid cultivated like desobjectifs of the plantation. In addition to the production of wood, the poplars are also largely used for the restoration of the grounds, as breaks wind, like barrier with the stranding, like parasol, for the animal feeds, the drug company, for the ornamentation or in phytoremediation.

cultures in alignments

The plantations in alignments are largely practiced throughout the world. They meet various more or less cumulable aims according to the cases. Alignments make it possible to combine production of sawlog and agricultural activity (culture or breeding) but this is far from being a their only function. Thus, they are largely used as windshield (in particular using P. will nigra VAr `Italica'), in the fight against the stranding, like tree of edge of roadway system (road, channels,…), for the shade or their decorative qualities.

The spacings vary according to the objectives allocated with alignment. In plantation windshield, the spacings vary between 2 and 4 Mr. In the fight against the stranding or in ground fixing, the densities can be largely increased (spacings between 0,5 m and 4 m). The plantations directed towards the production of sawlog have broader spacings (generally between 4 and 12 m).

The production in alignment is faster than in settlement but requires more maintenance if one wants to produce wood of great quality (sizes of formation, prunings and prunings more frequent). For example, in Belgium, the growth of the P.X euramericana `Robusta' is on average of 5 cm/an in settlement forest but easily reached 7 cm/an in alignment.

cultures with short rotations

This farming system became very in vogue throughout the world, the objective being the production of biomass in a time very runs for the cellulose production or more frequently like biocombustible. This type of woody production requires the same conditions as traditional agriculture: a work of the ground, weedkillers treatments (of pre-emergence and post-emergence) first years and after each harvest, sometimes of the insecticidal treatments (if attacks of insects défoliateurs) and of the relatively important contributions in manure. In the semi-arid and well shone upon areas, the irrigation or the fertirrigation is rather common there.

See too

Forest
Agrosylviculture
Paper mill

External bonds

Search engine on the poplar
the die of the Poplar in France
More on the genetic sequencing, published in SCIENCE in 2006
Description of the poplar on bois.be

Source

Stuck Samuel, 2006, the poplars throughout the world, Présentation of the species of the Populus kind, High Provincial School of Charleroi Université of Work, 276 p.

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