The reestablishment of forest cover either naturally or artificially. Given enough time, natural regeneration will usually occur in areas where temperatures and rainfall are adequate and when grazing and wildfires are not too frequent.
Reforestation occurs on land where trees have been recently removed due to harvesting or to natural disasters such as a fire, landslide, flooding, or volcanic eruption. When abandoned cropland, pastureland, or grasslands are converted to tree cover, the practice is termed afforestation (where no forest has existed in recent memory). Afforestation is common in countries such as Australia, South Africa, Brazil, India, and New Zealand. Although natural regeneration can occur on abandoned cropland, planting trees will decrease the length of time required until the first harvest of wood. Planting also has an advantage in that both tree spacing and tree species can be prescribed. The selection of tree species can be very important since it affects both wood quality and growth rates. Direct seeding is also used for both afforestation and reforestation, although it often is less successful and requires more seed than tree planting. Unprotected seed are often eaten by birds and rodents, and weeds can suppress growth of newly germinated seed. For these reasons, direct seeding accounts for only about 5% and 1% of artificial reforestation in Canada and the United States, respectively.
restoration of the main component of a forest, that is, trees, after which appear other characteristic components such as the soil cover, undergrowth, fungi, and bacterial flora. In practice, reforestation is judged from the presence and nature of the young generation of trees (shoots, bloom, self-seeding, seeds, regrowth, seedlings, undergrowth, root suckers), their number, geographical distribution, distribution by species, condition, and other signs. Reforestation may take place by the seed and vegetative methods or by natural, artificial, and combined methods.
Natural reforestation is not only a process of self-regeneration that takes place spontaneously but also is a controlled process. Therefore, natural reforestation in forestry is regarded as a method of regeneration (in practice it is frequently called assistance in natural regeneration); it includes such measures as protecting the seedling growth from injury during lumbering, leaving seed trees in clear-cut areas, and preparing the soil to provide conditions favorable for tree seeds reaching it. Natural reforestation is chiefly a biological process, one consisting of several stages from the formation of pollen and fertilization to the formation of dense stands of young trees. The process varies from one natural zone to another (in the fruiting times; in the conditions of seed germi-nation, sprouting, and subsequent formation of young trees; and especially in the recurrence of seed years). Thus, reforestation is both a biological and a geographical phenomenon. Since reforestation is regarded in practice both as a technical category and as a method of forest renewal whose applicability depends not only on natural geographical conditions but also on economic geographical conditions and possibilities, reforestation as a geographical phenomenon has acquired considerable practical significance in modern silviculture.
Artificial reforestation is accomplished by planting seeds or setting out seedlings. The choice depends on the species, natural conditions, availability of seeds and seedlings, and presence of mechanical equipment. Forest planting is gradu-ally increasing in modern silviculture.
Combined (mixed) reforestation is a combination of natural and artificial regeneration in the same place, including natural seeding regeneration combined with seeding or planting, natural regeneration of coniferous species with regeneration by shoots of deciduous species, regeneration by shoots of deciduous species with seeding of coniferous species, and so on.
Each method of reforestation has its advantages and disadvantages. The correct choice of method depends on the place and time. Artificial reforestation is carried out primarily in places where normal natural reforestation is not assured. The correlation of natural and artificial reforestation in mountainous and plains regions in the north differs from that in the south.
According to the type of cutting done, reforestation is divided into preliminary regeneration, that is, regeneration that occurs in a forest prior to cutting; concomitant regeneration, which also occurs under forest cover but as a result of the influence of selective cutting or gradual cutting; and subsequent regeneration, which occurs after clear-cutting a forest.
Reforestation must be distinguished from forestation, which is the establishment of a forest in an area where no forest had existed, such as on steppes, semideserts, deserts, and the sites of worked-out quarries and gravel pits.
I. S. MELEKHOV
an active form of forest renewal. Reforestation includes, above all, the artificial renewal of forests, as well as measures aimed at promoting and accelerating natural renewal and at improving the species composition and condition of the young generation of trees.
The goal of reforestation is to create high-yield forests. Thus, economically valuable species are cultivated: on the taiga, coniferous species (pine, spruce, larch, and Siberian cedar), and in the central and southern European USSR, oak and certain other deciduous species, as well as conifers, particularly pine. Valuable forms of soft-leaved species, such as Karelian birch and the fast-growing, healthy aspen, may also be used in reforestation. The concepts of “reforestation” and “forest renewal” are often used synonymously in forestry.