Tree planting is the process of transplanting tree seedlings, generally for forestry, land reclamation, or landscaping purposes. It differs from the transplantation of larger trees in arboriculture and from the lower-cost but slower and less reliable distribution of tree seeds. Trees contribute to their environment over long periods of time by improving air quality, climate amelioration, conserving water, preserving soil, and supporting wildlife. During the process of photosynthesis, trees take in carbon dioxide and produce oxygen. In silviculture, the activity is known as "reforestation", or "afforestation," depending on whether the area being planted has recently been forested or not. It involves planting seedlings over an area of land where the forest has been harvested or damaged by fire, disease, or human activity. Trees are planted in many different parts of the world, and strategies may differ widely across nations and regions and among individual reforestation companies. Tree planting is grounded in forest science and, if performed properly, can result in the successful regeneration of a deforested area. However a planted forest rarely replicates the biodiversity and complexity of a natural forest. Because trees remove carbon dioxide from the air as they grow, tree planting can be used to help limit climate change. Desert greening projects are also motivated by improved biodiversity and reclamation of natural water systems, as well as improved economic and social welfare due to an increased number of jobs in farming and forestry.
Types of trees planted
The type of tree planted may have great influence on the environmental outcomes. It is often much more profitable to outside interests to plant fast-growing species, such as eucalyptus, casuarina or pine (e.g., Pinus radiata or Pinus caribaea), even though the environmental and biodiversity benefits of such monoculture plantations are not comparable to native forest, and such offset projects are frequently objects of controversy. To promote the growth of native ecosystems, many environmentalists advocate only indigenous trees be planted. A practical solution is to plant tough, fast-growing native tree species which begin rebuilding the land. Planting non-invasive trees that assist in the natural return of indigenous species is called "assisted natural regeneration." There are many such species that can be planted, of which about 12 are in widespread use in the US. Alternatively, farmer-managed natural regeneration (FMNR), involves farmers preserving trees (not replanting), and is considered to be a more cost-effective method of reforestation than regular tree planting.
Season of planting
Bareroot stock The classical silvicultural literature unanimously advocates spring as the time to plant bareroot stock, with lifting and outplanting taking place while the trees are still apparently dormant. This view, in which spring planting is implicit, was epitomized by Toumey and Korstian (1942): "Almost without exception the most favourable time for ... planting is 2 weeks or more before buds [of the planting stock] begin their growth". Soil moisture conditions are generally favourable at the time when the growing season is about to begin, while dormant stock is less subject to mechanical injury and physiological shock. If the size of the planting program allows, there is little doubt that such scheduling would be advantageous in that it satisfies one, and commonly 2, of the factors essential for success: (1) the use of planting stock that is physiologically capable of responding to a growth environment at planting, and (2) planting when site factors favour tree survival and growth. The 3rd factor a good planting job, and although desirable in all plantings, is probably somewhat less critical in conventional spring plantings than at other times. If, however, a planting program cannot be completed in this way, there are other options: conventional fall planting with fresh-lifted stock; summer planting with fresh-lifted stock; and spring and summer planting with stored spring-lifted or fall-lifted stock.
Conventional spring planting with fresh spring-lifted stock In the context of regeneration silviculture, "spring", "summer", etc. lack precise meaning. Typically, the spring planting season begins as soon as lifting becomes possible in the nursery, and ends with the completion of the program. At this time, planting stock is physiologically attuned to the oncoming growing season, and the outplant has the whole of that season in which to establish its root system before it is challenged by any frost heaving. In practice, ideals are seldom attained. That stock is normally dormant when spring-planted is a widespread fallacy. Active growth is commonly obvious at the time of planting, but in any case the metabolic activity increases in planting stock before the tops give visible expression to this. The difficulty of obtaining, in quantity, spring-lifted stock in dormant condition increases with increasing continentality of climate. In many areas, the period of springlike weather is unreliable and often short. As well, the soil moisture advantage claimed for spring planting is also insecurely founded. Soils that are sandy or gravelly, and shallow soils of any texture are highly dependent on current weather due to their limited available water capacities. Nor will a plentiful supply of soil moisture benefit an outplant whose roots are enveloped in anaerobic and/or cold soil, and mortality of trees outplanted into soil colder than about 6 °C may be excessive. The spruces may be planted not only throughout the spring planting period provided that the period of most active shoot elongation is avoided, but virtually throughout the whole growing season, with little loss of performance other than some reduction in increment.
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