InSitu 95: Paper No 11
"Methods of selection work to improve the resistance factor of protective forests in Russia arid zone"
Index of Contents:
The principal targets for protective afforestation in Russia are regions with severe soil and climatic conditions, that is there is a lack of moisture, frequently recurring droughts, dry winds, freezing winters, salinity and alkalinity of the soils, and a susceptibility of the tree species to diseases and pests. All these factors create difficulties for the establishment of effective and resistant shelterbelts.
At the same time shelterbelts exert an extensive and positive effect on agriculture in arid zone of the contry. Shelterbelts contribute to increased yield of agricultural crops, protect the soil from water erosion and wind erosion, and so on. This paper summarizes the experience of the All-Russia Scientific Research Institute of Agroforestry Amelioration (VNIALMI) in breeding tree species that are utilized in Russia.
Breeding of Introduced Species
VNIALMI carries out the selection of the most resistant species in arboreta located in three regions. These arboreta, located in the arid zone, differ in regard to the tree growing conditions. The arboretum in the Central Povolzh'e (Samara city) was established in 1950 on ordinary loamy chernozems, has a mean annual temprature of 3.7 C (maximum +40 C, minimum -45 C), a relative humidity of 46% and a total precipitation of 395mm. The arboreta in the Lower Povolzh'e (Volgograd and Kamyshin) were established in 1910 and 1962 on chestnut soils, have a mean temperature of 5.4 to 7.6 C (maximum 41 to 43 C, minimum -35 to -39 C), a relative humidity of 40 to 41% and a total precipitation of 350 to 386mm. The arboretum in Western Siberia (Kulunda, Altai Territory) was established in 1977 on chestnut light-loamy soils, with a mean annual temperature of 1.9 C (maxium +41 C, minimum -50 C), a relative humidity of the air of 50% and a total precipitation of 270mm.
Of 281 species, hybrids and cultivars tested at Central Povolzh'e, the most promising for afforestation in the chernozem steppe were found to be: Betula pendula Roth, Quercus robur L, Larix sibirica Ledeb, Pinus sylvestris L, Populus pyromidalis X P. chinensis, P. pyramidalis X P. nigra, and P. balsamifera X P. berolinensis.
Of the 734 species, hybrids and forms that were tested in the Lower Povolzh'e arboreta, the most promising for field shelterbelts were: Robinia pseudoacacia L, Ulmus pumila L, Quercus robur L, Pyrus communis L, Gledistia triancanthos L, and Fraxinus lanceolata Borkh; for anti-erosion plantations: Crataegus species, Caragana arborescens Lam, Amorpha fruticosa L, Cotinus coggygira Scop and Ribes aureum Pursh; while for pasture-protecting shelterbelts: Crataegus monogyna Jacq, Colligonum sp., Halloxylon aphyllum (Minw.) Iijm, and Tamarix sp. Of 120 species, hybrids and forms tested in Western Siberia, the most promising have been acknowledged as: Betula pendula Roth, Pinus sylvestris L. and Ulmus laevis Pall. When the ground water is available to the roots, the greatest growth and a high winter hardiness were shown by the poplar hybrids: Populus pyramidalis X P. berolinensis and P. nigra X P. berolinensis X P. canadensis.
Plus Tree Selection The principal features, used for the superior populations, species and cultivars are drought, salt and frost resistance, as well as resistance to pest and diseases. Since in most regions there are no native populations of woody plants, the selection of the plus individuals or populations for protective afforestation is carried out in estabished old shelterbelt plantings, which during the process of their growth have undergone a systematic exposure to extreme conditions and, survived. Such a combination of unfavourable weather conditions has occurred during the past 20 years over an extensive area of the European part of Russia. The severe snowless winters of 1968/69 and 1971/72 and the severe droughts in 1972 and 1975 resulted in massive dieback of shelterbelts in the South-East of the European territory of the country. After such extereme years almost all of the shelterbelts were candidates for the selection of superior trees and shrubs. The serviving individuals and entire plantations provide a valuable gene pool for producing improved, hardy shelterbelt plantations. In addition, the native forests and "kolkas" which grow in depressed sectors of the topography are used in the improvement program. Their range occasionally extends into the regions of shelterbelt planting. These populations of tree species are also of considerable importance for breeding and seed peoduction purpeses. It is the sections of the natural forests on upland, dry sites that are targeted for the selection of parental (plus) populations and individual trees, even though in their growth and condition they are inferior to the sections of the stand growing on the bottom or on the lower part of the slope of the ravines. Finally, individual long-lived trees that have survived under severe conditions and which are growing in old forest belts, tree plantations, park and farms, should provide the basis for establishing seed plantations for protective afforestation. The plus trees that have been selected are marked with a ring and numbered, and registration plates are placed on them. Vegetatively and seed propagated test planting of these plus trees are established. After prolonged evaluation of their perfomance, conclusions are made concerning the quality of the selected gene pool. The best clones and populations are planted in seed orchards. The new progeny is more resistant and long-lived under severe growing conditions.On the basis of this method, VNIALMI has selected individual specimens of oak, elm, locust, pine and other trees, which are distinguished by a high resistance to drought, salinity, frost and diseases in the dry steppe and in semi-desert.
Breeding of Hybrids Further improvement in the ameliorative effect and longevity of shelterbelts under steppe conditions may be achieved by the introduction of hybrids of tree species. Work on hybridization in the field was initiated at the VNIALMI research station at Kamyshin in 1939 by A.V.Al'benski. At the present time hybrids of oak, pine, elm, ash and poplar have been developed that are especially promising for shelterbelt planting. As has been shown by studies conducted over many years, the majority of these species have superior growth and form. In the hybridization of oaks the pedunculate oak (Quercus robur L) was taken as the maternal tree, while the red oak (Q. rubra L) was taken as the pollinator. In the hybrids, the growth in height during the initial years was 1.5 times as great as in the parental species. At an age of 18 years the difference in height was 23.7 to 77.6%, while the difference in diameter ranged from 10.2 to 100.0%. On the basis of the intensity of transpiration, the accumulation of dry matter and the water-retaining capacity of the leaves, the hybrids occupy an intermediate position in comparison with both of the control species. Their heat tolerance is higher than that in the pedunculate and red oaks. In addition, the hybrids obtained have shown improved resistance to infection by vascular mycisis (a widely distributed disease of oak). For the hybridization of pines, the Scots pine (Pinus sylvestris L) and Crimean pine (P. Pallasiana Lamb.) were used. Both species were used as maternal trees and as pollinators. They are widely utilised for the afforestation of light soils, and in this case the Scots pine grows more rapidly, while the Crimean pine is more salt-tolerant. the average height of a 20 year old hybrid is 18 to 20% higher than that of either of the maternal species. The hybrid also surpasses the maternal species by 18% D.B.H. On the basis of the intensity of transpiration the hybrids occupied an intermediate position between the parental species. In the hybridization of elms, the Siberian elm (Ulmus pumila L)which was introduced from Central Asia, was used as the maternal tree. This species is distinguished by its rapid growth, drought and salt resistance, but is not fully frost hardy. The progeny obtained from the pollination of this species with the pollen of the smooth-leaves elm (U. carpinifolia Rupp) and the "common" elm (U. laevis Pall.) markedly exceeded the parental species in their growth. The heterosis in growth was retained also in the third seed generation. The drought resistance in the hybrids obtained was also higher than in the parental specias. Of special importance to field shelterbelt afforestation is the poplar (Populus sp.), which is distinguished by its rapid growth and great height. The hybrids with a pyramidal form allow one to allocate a minimal area to the shelterbelts and especially valuable for afforestation on irrigated lands. Twenty six crossing combinations of this tree were carried out by A.V.Al'benski and his students from 1933. The most successful of these were: white X Bolle (P.alba X P. bolleana); pyramidal X Berlin (P. pyramidalis X P. berolinensis); pyramidal X Chinese (P. pyramidalis X P. chinensis), Balsam and Berlin (P. balsamifera X berolinensis), and Moscow and "krasnonervnyi" No. 1191. All of these successfully survived the severe winter of 1968/1969 and extremely dry summer of 1972, and they had an indisputable superiority over the parental species on the basis of their morphological features.
Organization of Forest Seed Production Shelterbelt planting in Russia is carried out over a large territory with various soil and climatic conditions. On the basis of the directions of the breeding work and the organization of the forest seed production, three large regions are distinguished: 1) forest-steppe and chernozem steppe, 2) dry steppe, and 3) semi-desert. The first two regions have concentrated on establishment of field shelterbelts and water-regulating forest belts in agricultural fields, anti-erosion forest plantations in ravines and gullies and afforestation of lands that have a low productivity (sands, waste piles, quarries, etc.). In the forest-steppe and chernozem steppe regions, which are characterized by comparatively good forest growth conditions, it is necessary to introduce into the shelterbelt plantations tall trees that form open and permeable belts, which exert the best effect on the microclimate of the fields. To these belong the pine (Pinus sp.), larch(Larix sibirica), oak, birch, Norway maple (Acer platanoides), linden (Tillia sp.) and poplar (Populus sp.). Seed plantations of these tree species are established with consideration given to the overall requirement for protective afforestation. Seed orchards in this region are established from progeny of the better local and the tested introduced populations. By the establishment of special seed orchards there is a more reliable seed supply, a reduction in the damage caused by pests and diseases and some improvement in the gene pool of the most drought, salt and frost resistant. In the dry steppe regions with dark-chestnut soil the belts of trees on the fields are mainly oak (Quercus sp.) and their hybrids. On chestnut and light-chestnut soils, the best are Siberian elm (Ulmus pumila), locust (Robiniapseudo acacia), ash (Fraxinus), hawthorn (Crataegus), olive (Elaeagnus) and golden currant (Ribes aureum), while on light soils pine (Pinus) is mainly used. The seed plantations are also established with consideration given to the overall requirements of trees and their function in the region. In the semi-desert zone if the country the principal type of shelterbelt planting is pasture plantations. For the creation of ameliorative plantations of green caponies for relaxation of animals, drought and salt resistant shrubs, such as saxaul (Haloxylon), "dzhuzgun" (Colligonum) and tamarisk (Tamariz) are utilized. Furthermore, in order to improve their productivity, woody foliage plants such as winterfat (Eurotia), saltwort (Salsola) and others are planted. Seeds are obtained from established seed plantations from a quality-controlled gene pool of these species.
1. A basic condition for the growing of long-lived shelterbelt plantations within the arid treeless zone involves the utilization of a particular composition of woody plants, which may be introdused species, that are most completely adapted to the soil and climatic conditions of a particular geographical locality. 2. Additional improvement in the resistance of artificial plantations may be attained by: (a) the plus tree selection of the principal tree species that are used for protective afforestation; (b) interspecific hybridization of the tree species; (c) the proper selection of the direction of the shelterbelt planting (field or pasture-protecting, anti-erosion, sand-consolidating, etc.) and the correct organization of the silvicultural seed production in different natural conditions in the the arid zone. 3. For the establishment of maternal seed plantations, use is made of a genetically valuable gene pool, that is distinguished by an elevated resistance to drought, frost, the salt content in the soil, pests and diseases.