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strips of trees and shrubs artificially created by planting or sowing to protect crop fields, soils, bodies of water, roads, and population centers from unfavorable natural factors. Shelterbelts are grown mostly in steppe, forest-steppe, and semidesert regions.
In Russia, the home of steppe forestation, forests began for the first time to be cultivated on the open steppe in 1696 by order of Peter I—for example, the Dubki grove near Taganrog. Shelterbelts were created on a larger scale in arid regions in the late 18th and early 19th centuries. Between 1804 and 1817 the landowner I. la. Danilevskii planted about 1,000 desiatinas (1,090 hectares [ha]) of pine forests on the sands along the Severskii Donets River. The landowners V. la. Lomikovskii (from 1809, Poltava Province) and V. P. Skarzhinskii (from 1812, Kherson Province) also engaged in forestation for protective purposes. The landowner I. N. Shatilov planted gully and ravine Shelterbelts (from 1821). Military settlements in the southern Ukraine played a major role in creating Shelterbelts in treeless regions, and more than 17,000 desiatinas (18,530 ha) of artificial forests were planted in these regions from 1817 to 1857, mostly on sands. Experi-mental work in steppe forestation began in 1843 with the creation of the Veliko-Anadol’ Forestry Area (in present-day Donetsk Oblast) headed by the forester V. E. Graff. Efficient methods of forestation were developed in Russia by the foresters L. G. Bark, A. A. De-Karier, Kh. S. Polianskii, F. F. Tikhonov, N. la. Dakhnov, and K. N. Genko; and N. K. Sredinskii established Shelterbelts along railroads.
An expedition led by V. V. Dokuchaev (1892–98) laid the foundation for scientific research on the nature of steppes and on the possibilities and methods of growing Shelterbelts on them.
Protective forestation was little developed before the Great October Revolution. Only 130,000 ha of Shelterbelts were planted prior to 1917. In the Soviet period there has been an increase in the area devoted to experimental land reclamation through forest planting, in the number of agricultural and ravine stations, and in the forestry area for developing methods of creating Shelterbelts to control drought and water and wind erosion; methods of restoring the fertility of eroded soils have been improved. The effect of Shelterbelts on runoff, microclimate, snow distribution, and the hydrological regime of the soil has been described. Methods of growing Shelterbelts, the various types of Shelterbelts, and their design, width, and distribution on agricultural land are being worked out, and the selection of trees and shrubs used in planting Shelterbelts is being determined. G. N. Vysotskii, N. I. Sus, and A. S. Kozmenko have made important contributions to the theoretical working out of these problems. In 1968 there were more than 2 million ha of Shelterbelts in the USSR, including over 800,000 ha of field and 540,000 ha of gully-ravine Shelterbelts and 615,000 ha planted on sand.
Shelterbelts include the field-protecting forest strips planted on sovkhozes, kolkhozes, and other farms along the edges of crop rotation fields (on and within large fields). They diminish the velocity and turbulence of winds on adjacent fields, improve the microclimate, snow distribution, and soil moisture, and protect the soil against wind and water erosion, thereby increasing crop yields. On plowed slopes of more than 2° field-protecting strips, by reducing meltwater and rainwater runoff and the washing away of soil, play an important part in water regulation; these are called water-regulating Shelterbelts.
On irrigated lands Shelterbelts are planted along irrigation ditches in narrow strips of one to four rows of trees on one or both sides; along ditches outside irrigated areas, trees are planted in five, six, or more rows. These strips reduce unproductive losses of moisture by evaporation from ditches and fields, intercept water percolating from ditches, and prevent both the rise of groundwater and secondary soil salinization. The strips also protect crops against dry winds and dust storms, prevent ditches from filling up with fine earth, and prevent the edges of ditches from becoming overgrown with weeds. Shelterbelts are planted around ponds to prevent them from evaporating and silting; they consist of strips of trees and shrubs (10–20 m wide) above the highwater mark and, if the banks are planted steep, above the brow of hollows. On dams one- or two-row stabilizing and shading shelterbelts, mostly of white willow, are planted on the wet slopes. Shrubs, acting as silt filters, are planted on the part of water-conducting thalwegs (20–50 m long and the entire width of a flood) that is closest to the water surface.
Near-ravine and near-gully Shelterbelts are grown along the brows of gullies and ravines in strips 15–30 m wide. They reduce runoff, stabilize the soil by preventing erosion, and promote the agricultural use of marginally productive land. If the gulleys and ravines border on arable land, near-gully and near-ravine Shelterbelts also serve as field-protecting strips. Ravine and gully Shelterbelts, either continuous or in groves, are planted on the slopes of ravines and eroded gullies and along their bottoms to prevent the further erosion of gulleys and ravines. Water-regulating Shelterbelts on slopes, near-ravine and near-gully Shelterbelts, and gully and ravine shelterbelts all help control soil erosion. Strip, grove, windbreak strip, and tract Shelterbelts are planted on sand to prevent them from being blown away by winds and to promote the agricultural use of sandy areas.
Shelterbelts around orchards and various types of plantations and nurseries consist of three to five rows of trees and Shelterbelts within them of one or two rows. They have a favorable effect on the growth and productivity of crops. Shelterbelts on pastures, around livestock breeding farms and in the resting places of livestock are laid out in the form of strips and groves. Strip plantings increase the productivity of pastures and protect livestock breeding farms against cold winds and snow drifts. Cross-shaped Shelterbelts on pastures protect cattle against cold winds. Groves are laid out mostly in the form of green umbrellas to protect cattle against hot sun.
Shelterbelts along railroads protect them from snow and sand drifts, stabilize steep slopes and eroded banks, blunt the force of strong winds, and keep cattle away from the tracks. Snow-retaining shelterbelts are laid out according to the estimated amount of snow carried to each side of the railroad track and are usually planted on both sides of the tracks. They consist of a wide strip or of several narrow parallel ones. Sand-stabilizing shelterbelts along railroads are arranged in a pattern of strips of trees and shrubs combined with grass. Soil-stabilizing shelterbelts may take such forms as strips and tracts and are usually combined with drainage ditches. Windbreaks are planted in areas exposed to strong side and head winds. They greatly reduce wind velocity along railroad tracks and are patterned after snow-retaining shelterbelts. Protective shelterbelts are made from willow pickets forming a screen impenetrable to cattle.
Shelterbelts planted along highways as protection against snowdrifts consist of one or two narrow strips of four to six rows, each situated 20–80 m from the road depending on the amount of snow.
Shelterbelts in the form of forest tracts, broad forest strips, or a network of narrow forest strips are planted around cities and other inhabited areas to protect these areas against dust storms and strong winds. They are usually combined with parks, private and public gardens, and boulevards.
REFERENCESLesnye zashchitnye nasazhdeniia. Moscow, 1963.
Instmktivnye ukazaniia po proektirovaniiu i vyrashchivaniiu zashchitnykh lesnykh nasazhdenii v ravninnykh raionakh SSSR.Moscow, 1966.
Senkevich, A. A. Ekonomika zashchitnogo lesorazvedeniia. Moscow, 1969.
G. I. MATIAKIN
narrow strips of artificial protective plantings in plowed fields and along railroad tracks, automobile highways, and irrigation and navigation channels. Their purpose is to prevent dry winds from damaging crops, improve water conditions in the soil by retaining snow and reducing evaporation, prevent soil erosion, and protect railroad tracks and automobile highways against snow and sand drifts.