“Tree planting”的意思、由来-开放百科全书

Tree-planting is the process of transplanting tree seedlings, generally for forestry, land reclamation, or landscaping purpose. It differs from the transplantation of larger trees in arboriculture, and from the lower cost but slower and less reliable distribution of tree seeds.

In silviculture the activity is known as reforestation, or afforestation, depending on whether the area being planted has or has not recently been forested. It involves planting seedlings over an area of land where the forest has been harvested or damaged by fire, disease or human activity.

Tree planting is carried out 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. Reforestation is the commercial logging industry's answer to the large-scale destruction of old growth forests, but a planted forest rarely replicates the biodiversity and complexity of a natural forest.{{Citation needed|date=August 2011}}

Because trees remove carbon dioxide from the air as they grow, tree planting can be used as a geoengineering technique to remove {{CO2}} from the atmosphere. Desert greening projects are also motivated by improved biodiversity and reclamation of natural water systems, but also improved economic and social welfare due to an increased number of jobs in farming and forestry.

By country

Australia

Australian forests have been heavily affected since European colonisation, and some attempts been made to restore native habitats, both by government and individuals. Greening Australia is a national Non profit set up to run the "National Tree Program" initiated by the Federal Government in 1982.^[1] Greening Australia completed the 1 Billion Tree target and has gone on to become one of the major tree planting organisations in the country.

There is a strong volunteer movement for conservation in Australia through Landcare and other networks. National Tree Day is organised annually by Planet Ark in the last week in July, encouraging the public to plant 1 million native trees per year. Growing trees for Timber industries is a long-term project. It may take many years for a tree to mature to an age and size that is appropriate for the Timber to be used by industry. Some trees are many hundreds of years old.

Many state governments run their own "Million Tree" programs each year to encourage community involvement.^[2]^[3]

Canada

Most tree planting in Canada is carried out by private reforestation companies.^[4] The reforestation companies compete with one another for contracts which are provided by logging companies. The annual allowable cut for the following year is based upon how much money the logging company invests into reforestation and other silvicultural practices. Planting is carried out in accordance to the client's specifications, and planters are expected to learn the quality standards for each contract that they work on. Planted blocks are spot checked on a regular basis. Although quality concerns vary across contracts, spot checkers are typically looking for such things as: species appropriate site choice, species appropriate spacing, how tight the saplings are in the ground, how straight the saplings are, and whether or not the saplings have been damaged. These concerns vary from region to region, and from contract to contract.

Tree-planting is typically piece work and tree prices can vary widely depending on the difficulty of the terrain and on the winning contract's bid price. As a result, there is a saying among planters: "There is no bad land, only bad contracts." 4 months of hard work can yield enough to live on for an entire year, but conditions are harsh.^[4]

Tree planting crews often do not permanently reside in the areas where they work, thus much planting is based out of motels or bush camps. Bush camp accommodations usually consist of a mess tent, cook shack, dry goods tent, first aid tent, freshly dug outhouses, and a shower tent or trailer. Planters are responsible for bringing either a tent or car to sleep in. A camp also contains camp cooks and support staff.^[4]

The average British Columbian planter plants 1 600 trees per day,^[7] but it is not uncommon for experienced planters to plant up to 4,000 trees per day while working in the interior.^[4] These numbers are higher in central and eastern Canada, where the terrain is generally faster, however the price per tree is slightly lower as a result. Average daily totals of 2500 are common, with experienced planters planting upwards of 5000 trees a day. Numbers as high as 7500 a day have been recorded.^[4] Planters typically work 8–11 hours per day with an additional 1 to 2 hours of (usually) unpaid traveling time. Work weeks on British Columbian planting contracts are usually 4–5 days long, with 1–2 days off. In Ontario, work weeks are generally 5–6 days long, with 1 day off.

Quite often, tree planting contractors will deduct some of the cost associated with the operation of the contract directly from the tree planter's daily earned wages. These imposed fees typically vary from $10 to $30 per day, and are referred to as "camp costs". In some cases, rookie tree planters end up owing their employer money for the first few pay periods.^[5]

Once inflation is factored in, real tree planter earnings have declined for many years in Canada. This has adversely affected the sector's ability to attract and retain workers.^[6] Higher wages and much better working conditions in many other industries, from construction, to oil and gas, and even information technology, has led to fewer Canadian young people wanting to plant trees.

Based on statistics for British Columbia, the average tree planter: lifts a cumulative weight of over {{Convert|1000|kg|lb}}, bends more than 200 times per hour, drives the shovel into the ground more than 200 times per hour and travels over {{Convert|16|km|mi}} with a heavy load, every day of the entire season. The reforestation industry has an average annual injury rate of approximately 22 claims per 100 workers, per year. It is often difficult and sometimes dangerous.^[7]

Great Britain

Planting in Britain is commonly referred to as restocking, when it takes place on land that has recently been harvested. When occurring on previously unforested land it is known as new planting.^[8] Under the British system, in order to acquire the necessary permissions to clearcut, the landowner must agree a management plan with the Forestry Commission (the regulatory body for all things forestry) which must include proposals for the re-establishment of tree cover on the land. Planting contractors will be engaged by the landowner/management company, a contract drawn up and work will typically take place from November to April when most of the transplants are dormant.

Planting is part of the rotational nature of much British plantation forestry. Productive tree crops are planted and subsequently clearcut. Some form of soil cultivation may take place and the ground is then restocked. Where the production of timber is a management priority, a prescribed stocking density must be achieved. For coniferous species this will be a minimum of 2500 stems per hectare at year 5 (from planting). Planting at this density has been shown to favour the development of straighter knot-free logs.

Planters are normally paid under piece work terms and an experienced worker will plant around 1500 trees a day under most conditions.

Israel

Tree-planting is an ancient Jewish tradition. The Talmudic rabbi Yohanan ben Zakai used to say that if a person planting a tree heard that the Messiah had arrived, he should finish planting before going to greet him.^[9] With over 240 million planted trees, Israel is the only country that entered the 21st century with a net gain in the number of trees. Due to massive afforestation efforts,^[10] this fact echoed in diverse campaigns.^[11]^[12] Israeli forests are the product of a major afforestation campaign by the Jewish National Fund (JNF).^[13]

The largest planted forest in Israel is Yatir Forest, located on the southern slopes of Mount Hebron, on the edge of the Negev Desert. It covers an area of 30,000 dunams (30 square kilometers).^[14] It is named after the ancient Levite city within its territory, Yatir, as written in the Torah: "And unto the children of Aaron the priest they gave Hebron with its suburbs, the city of refuge for the manslayer, and Libnah with its suburbs, and Jattir with its suburbs, and Eshtemoa with its suburbs" (Book of Joshua 21:13-14).^[15] In 2006, the JNF signed a 49-year lease agreement with the State of Israel which gives it control over 30,000 hectares of Negev land for the development of forests.^[16] Research on climate change is being carried out in Yatir Forest.^[17]^[18] Studies of the Weizmann Institute of Science, in collaboration with the Desert Research Institute at Sde Boker, have shown that the trees function as a trap for carbon in the air.^[19]^[20] Shade provided by trees planted in the desert also reduces evaporation of the sparse rainfall.^[19] Yatir Forest is a part of the NASA project FluxNet, a global network of micrometeorological tower sites used to measure the exchanges of carbon dioxide, water vapor, and energy between terrestrial ecosystem and atmosphere. The Arava Institute for Environmental Studies conducts research that focuses on crops such as dates and grapes grown in the vicinity of Yatir forest.^[21]^[22] The research is part of a project aimed at introducing new crops into arid and saline zones.^[23]

The JNF has been criticized for planting non-native pine trees which are unsuited to the climate, rather than local species such as olive trees.^[24] Others say that JNF deserves credit for this decision, and the forests would not have survived otherwise.^[25]{{Better source|date=December 2013}} According to JNF statistics, six out of every 10 saplings planted at a JNF site in Jerusalem do not survive, although the survival rate for planting sites outside Jerusalem is much higher – close to 95 percent. Critics argue that many JNF lands outside the West Bank were illegally confiscated from Palestinian refugees, and that the JNF furthermore should not be involved with lands in the West Bank.^[26] Shaul Ephraim Cohen has claimed that trees have been planted to restrict Bedouin herding.^[27] Susan Nathan wrote that forests were planted on the site of Arab villages after the 1948 war.^[28] Nathan also writes that olive trees were replaced by pine and cypress trees^[29] and that JNF afforestation policy is a mean to erase traces of the Arab presence prior to 1948.^[30]

Since 2009, the JNF has provided the Palestinian Authority with 3,000 tree seedlings for a forested area being developed on the edge of the new city of Rawabi, north of Ramallah.^[31]

New Zealand

Kaingaroa Forest in New Zealand is the second largest planted forest in the southern hemisphere after the Sabie/Graskop area in South Africa. It is one of the many plantation forests planted since European settlement. The Monterey Pine (Pinus radiata) is commonly used for plantations since a fast-growing cultivar suitable for a wide range of conditions has been developed.

Government agencies, environmental organisations and private trusts carry out tree planting for conservation and climate change mitigation. While some work is carried out by private enterprise, there are also planting days organised for volunteers. Landcare Research use planted forests for their EBEX21 system for greenhouse gas emissions mitigations.^[32]

South Africa

South Africa's forests have been a heavily depleted mostly due to agriculture, traditional farming and urbanisation in the coastal regions . Various organizations are working on increasing the forest cover in parts of the country. Currently there is less than 0.5% forest cover in South Africa. Wildlands Conservation Trust and Food & Trees for Africa (FTFA) are some of the oldest NGOs working to plant trees throughout South Africa - both established in the early 1990s. Greenpop is a national Social Enterprise set up to run a "Tree Planting Program" greening both urban and rural areas. This was initiated in 2010. There is a strong volunteer movement for conservation in South Africa. National Tree Day or Arbor Day is organised annually in September, and has gone on to become national Arbor Month.

The largest planted forest in the Southern Hemisphere is located in the Sabie/Graskop area in South Africa and covers approximately 6000km² ^[33]

United States of America

Trees for the Future and Plant With Purpose are non-profit organizations based in the U.S. that plant trees in developing countries to improve land management.^[34]^[35] Other organizations that plant trees in the United States include:

India

Tree Plantation drives combat many environmental issues like deforestation, erosion of soil, desertification in semi-arid areas, global warming and hence enhancing the beauty and balance of the environment. Trees absorb harmful gases and emit oxygen resulting in increase in oxygen supply.

On an average, a single tree emits 260 pounds of oxygen annually. Similarly, a fully-grown tree is sufficient for 18 human beings in one acre of land in one year stressing the importance of tree plantation for mankind. Aniruddha’s Academy of Disaster Management (Mumbai, India) carries out numerous projects to plant trees on huge scale. The foundation trains volunteers on this subject at Govidyapeetham (Cattle Conservation Institute) in the city of Karjat in Maharashtra, India. The trained volunteers then plant saplings, trees in groups in available land. Local government authorities also provide vacant plots, land on highways sides and on the hills for tree plantation.

Role in climate change

The development of markets for tradeable pollution permits in recent years have opened up a new source of funding for tree planting projects: carbon offsets. The creation of carbon offsets from tree planting projects hinges on the notion that trees help to mitigate climate change by sequestering carbon dioxide as they grow. However, the science linking trees and climate change is largely unsettled, and trees remain a controversial source of offsets.

Climate impacts

Climate scientists working for the IPCC believe human-induced global deforestation is responsible for 18-25% of global climate change. The United Nations, World Bank and other leading nongovernmental organizations are encouraging tree planting to mitigate the effects of climate change.

Trees sequester carbon through photosynthesis, converting carbon dioxide and water into molecular dioxygen (O₂) and plant organic matter, such as carbohydrates (e.g., cellulose). Hence, forests that grow in area or density and thus increase in organic biomass will reduce atmospheric CO₂ levels. (Carbon is released as CO₂ if a tree or its lumber burns or decays, but as long as the forest is able to grow back at the same rate as its biomass is lost due to oxidation of organic carbon, the net result is carbon neutral.) In their 2001 assessment, the IPCC estimated the potential of biological mitigation options (mainly tree planting) is on the order of 100 Gigatonnes of carbon (cumulative) by 2050, equivalent to about 10% to 20% of projected fossil fuel emissions during that period.^[41]

However, the global cooling effect of forests from carbon sequestration is not the only factor to be considered. For example, the planting of new forests may initially release some of the area's existing carbon stores into the atmosphere. Specifically, the conversion of peat bogs into oil palm plantations has made Indonesia the world's third largest producer of greenhouse gases.^[42]

To date, most tree planting offsets strategies have taken only the first effect into account. A study published in December 2005 combined all these effects and found that tropical forestation has a large net cooling effect, because of increased cloudiness and because of high tropical growth and carbon sequestration rates.^[43]

Trees grow three times faster in the tropics than in temperate zones; each tree in the rainy tropics removes about 22 kilograms (50 pounds) of carbon dioxide from the atmosphere each year.^[44] However, this study found little to no net global cooling from tree planting in temperate climates, where warming due to sunlight absorption by trees counteracts the global cooling effect of carbon sequestration. Furthermore, this study confirmed earlier findings that reforestation of colder regions — where long periods of snow cover, evergreen trees, and slow sequestration rates prevail — probably results in global warming. According to Ken Caldeira, a study co-author from the Carnegie Institution for Science, "To plant forests outside of the tropics to mitigate climate change is a waste of time.".^[45]

His premise that grassland reflects more sun, keeping temperatures lower, is, however, applicable only in arid regions. A well-watered lawn, for example, is as green as a tree, but absorbs far less CO₂. {{Citation needed|date=September 2007}} Deciduous trees also have the advantage of providing shade in the summer and sunlight in the winter; so these trees, when planted close to houses, can be utilized to help increase energy efficiency of these houses.

This study remains controversial and criticized for assuming dark colored trees might replace the frozen, white tundra in the upper northern hemisphere. Regular tree planting projects typically take place on lands that are only slightly different in color. The warming impact was also measured over hundreds of years, rather than a 30- to 70-year time horizon most climate experts believe we have to fix climate change.

Furthermore, the described warming effect (of temperate and boreal latitude forest) is only apparent once the trees have grown to create a dense 'close canopy', and it is at precisely this point that trees grown for offset purposes should be harvested and their absorbed carbon fixed for the long-term as timber.

Costs

While the benefits of tree planting are subject to debate, the costs are low^[46] compared to many other mitigation options. The IPCC has concluded that "The mitigation costs through forestry can be quite modest (US$0.1–US$20 / metric ton carbon dioxide) in some tropical developing countries.... The costs of biological mitigation, therefore, are low compared to those of many other alternative measures".^[41] The cost effectiveness of tropical reforestation is due not only to growth rate, but also to farmers from tropical developing countries who voluntarily plant and nurture tree species which can improve the productivity of their lands.^[47] As little as US$90 will plant 900 trees, enough to annually remove as much carbon dioxide as is annually generated by the fossil-fuel usage of an average United States resident.

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, such as Leucaena leucocephala.^[48]

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.^[49] This view, in which spring planting is implicit, was epitomized by Toumey and Korstian (1942):^[50] "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.^[51]

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.^[49]

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 spring-like 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.^[52]^[53] Flushing increases the vulnerability of planting stock to both physiological stress (because of increased water requirements and reduced root growth capacity) and mechanical damage, which probably accounts for the commonly asserted superiority of early spring over late spring planting.

In fact, 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. Mullin's (1971)^[54] study at Midhurst in southern Ontario illustrates both the success with which white spruce can be planted throughout the period in question and the need to minimize stresses on the planting stock. Mullin used 3+0 stock from regular shipping beds in a series of 6 weekly plantings beginning with apparently dormant trees on 3 May and ending on 7 June, by which time the new leading shoots were several centimetres long. Trees were lifted with and without root dipping, planted on the day of lifting after their root systems had been exposed for 0, 1, 2, or 3 hours. Whereas 2nd year survival in the control (root exposure = 0) condition varied little among the 6 plantings, with averages of 83.5% +/- 4.7% for root-dipped trees and 77.2 +/- 7.0% for non-dipped, mortality rates among root-exposed stock were very much more variable. For instance, 2nd-year survival among root-dipped trees whose root systems had been exposed for 1 hour varied from 17% to 84%.

Conventional fall planting with fresh-lifted stock

The fall planting season is generally considered to begin when nursery stock has hardened off and soil moisture reserves have been replenished by autumnal rain. It then continues until the planting program has been completed or is terminated by freeze-up or heavy snow. The advantages of fall planting were once considered "To outweigh those of spring so certainly" that in the National Forests of the Lake States almost all planting was done in the fall,^[55] but in spite of some success, operational fall plantings in North America have tended to be less successful than operational spring plantings.^[56] On certain sites, a major disadvantage of fall planting is that the root systems of outplants have little time in which to become firmly anchored before being subjected to frost heaving. Such plants are also vulnerable to "winter browning", which in fact may occur in the fall soon after planting, especially among stock having high shoot:root ratios.^[57] Relationships between dormancy progression and physiological condition, including root-growth capacity, are much less clear in the spruces than in the pines, but certainly there is good evidence^[58]^[59]^[60]^[61]^[62] that, in the absence of frost heaving, plantings of spruces can be just as successful in fall as in spring.

Summer planting with fresh-lifted stock

Conceptually and logistically, the simplest way of extending the conventional planting season is to extend lifting and planting of fresh stock through summer until the planting program has been competed. There is evidence that spruces may be planted successfully throughout the summer.{{citation needed|date=October 2017}} Summer planting has also been successful in a number of research studies with white spruce, e.g., Crossley 1956;^[63] Ackerman and Johnson 1962;^[64] Decie 1962 cited by Revel and Coates 1976;^[65] Burgar and Lyon 1968;^[66] Mullin 1971,^[54] 1974;^[67] Revel and Coates 1976.^[65] Success depends on minimizing stresses to planting stock at all stages from lifting through planting and on planting when site conditions are conducive to survival and growth.

Spring and summer planting with stored stock

Refrigerated storage of planting stock has been developed largely with the aim of overcoming problems experienced in using flushed planting stock. Storage provides a means of holding stock for use when fresh stock is either unavailable or at a stage of development that renders it unsuitable for planting. It also offers possibilities of manipulating the physiological condition of the stock. However, there are problems associated with storage, e.g., mold, cold injury, desiccation, and depletion of food reserves. The rate of deterioration depends very much on the physiological condition of the planting stock at the time of lifting, as well as on the storage environment and duration of storage. In attempts to devise safe schedules for spring-lifting of stock for frozen storage, Mullin (1978)^[68] used a base of 0 °C and accumulated daily maximum soil temperatures at 15 cm depth to calculate degree days (DD). He interpreted the evidence to mean that white spruce destined for frozen storage should have accumulated no more than 50 DD before being lifted. With regard to cool-stored, spring-lifted stock, the main ingredients for success are lifting before flushing has begun, prevention of desiccation, maintenance of a constant temperature within 1 or 2 degrees of freezing, minimization of mold by good temperature control and sanitation, avoidance of crushing and other mechanical damage, and avoidance of longer than necessary periods of storage.

Mullin and Forcier (1976)^[69] and Mullin and Reffle (1980)^[70] examined the effects of spring-lifting date and planting date on several species, including 3+0 white spruce after frozen storage, with fresh-lifted controls planted on each planting date for comparison. In all plantings, the earliest (2 May) lifting gave highest average second-year survival in all species. In another study, Mullin (1978)^[68] found that outplantings of frozen-stored 3+0 white spruce were consistently successful to the end of July only with the earliest -lifted (25 April) stock. Sutton (1982)^[71] also used 3+0 white spruce in outplanting every 2 weeks from the end of June through the growing season in 3 successive years on a variety of sites in northern Ontario. Despite variation in planting stock, poor storage environments and adverse weather, 4th-year results showed a consistent pattern of reasonable survival and growth rates among trees planted through July, with a rapid decline in performance of trees planted thereafter. Overwinter storage of stock has also been employed. It has the advantage of lifting stock at the end of the growing season when physiological processes are invoking natural dormancy. Time of fall lifting was investigated by Mullin and Parker (1976)^[72] along with overwinter storage temperature to determine their effects on the performance of spring-planted 3+0 white spruce. There were 5 lifts, weekly from 19 October through 16 November, after which frozen ground put a stop to lifting. Two storage temperatures were used, -18 °C and -4 °C. Nearly all of the trees stored at -18 °C died. The other stock was planted in shallow furrows in sparsely sodded field of loamy sand on 12 April, 17 May, and 14 June along with fresh-lifted stock on each date. Fresh and stored white spruce gave comparable results in plantings extended into mid-June in the Midhurst area of Ontario.

Natural refrigerated overwinter storage has been used in root cellars and snow caches. Using natural refrigeration in root cellar storage, Jorgensen and Stanek (1962)^[73] kept 3+0 and 2+2 white spruce in dormant condition for 6 months without apparent detriment to performance after outplanting. Moreover, the stock was highly resistant to spring frost damage. Natural cold storage for overwintering 3+0 and 2+2 white spruce was also used by Mullin (1966).^[74] Unlike Jorgensen and Stanek's (1962)^[73] stock, which was raised 550 km to the south of where it was planted, Mullin's stock was raised in a nursery at about the same latitude as the planting site; the stock experienced inside-bale temperatures down to -15 °C in mid-winter, but still showed first- and second-year survival rates of 85.9% and 65.9%, respectively, compared with 91.4% and 76.2%, respectively, for fresh-lifted stock. However, Mullin's stored stock was much more damaged by spring frost than was fresh-lifted stock and it "showed a reduction in vigour as measured in terms of survival, susceptibility to damage and growth".

See also

References

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