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Reforestation
What Is Reforestation?
This section summarizes the mechanics of reforestation and focuses on pertinent issues and problems that may prevent reforestation success.
Reforestation, just like deforestation, comes in all sizes and shapes. The easiest is just allowing the birds, animals, wind and rain to distribute seeds from nearby healthy habitats to less forested or regenerating areas. This process takes a lot longer to enjoy the benefits and often is limited in biodiversity to species presently occurring in the immediate areas or areas uphill or upstream. One can always increase bio-diversity in naturally regenerating forests and address the need for food producing trees by planting in specifically desired species within regenerating forest.
Alternatively, when land is devoted purely to pastureland and one does not want to wait for nature to work its magic, native species appropriate to altitude and site can be planted to create a forest matrix over time. Mixing as many species together that were commonly in the region prior to deforestation is critical and planting appropriate species near water features goes a long way to insuring health for future generations of plants, animals and humans.
Finally, one can engage in sustainable native tree farming on open pastureland, taking care to space trees properly for optimal growth rates depending on the species and site requirements. Although these trees will be cut one day for money, they are still sequestering CO2 for eternity as long as they are not burned. Incorporating biological corridors in all reforestation projects is critical to avoid clear cuts which are never recommended and preserve the integrity of the land and water.
Land preparation
The degree and type of land preparation depends on several factors: site and soil conditions, vegetation cover, species to be planted, and available capital and labor. In Costa Rica, especially in the mountains, land preparation is done by hand, specifically with machete. This notably provides temporary employment to local laborers and causes minimal damage to soil and surrounding vegetation. In Costa Rica, especially in the mountainous areas, planting my machine is not a practical option. However, the disadvantage of manual clearing is the need to recruit, manage, and provide logistical support in remote areas for large numbers of laborers.
In the tropics and unlike many styles of mechanized reforestation or tree farming practices in the United States and Canada, it is not necessary to clear stumps and competing weedy vegetation. To the contrary, the presence of vegetative cover assists greatly in protecting young tree saplings from rainy season downpours and hot burning sun, especially the first three years of the tree’s life. Indeed, many rainforest species in danger of extinction will not tolerate full sun. Shade is necessary and easily created from surrounding vegetation allowed to remain.
Land preparation and project design are always determined on a case by case basis, depending on the steepness and quality of soil and surrounding vegetation. Dividing into categories of pasture and secondary forest or charral is easiest to understand and in keeping with the analysis made for application of tree cutting laws. To maintain surrounding vegetation critical for shade in early years, swaths or paths are cut into the grass with all surrounding grasses and vegetation allowed to remain. Alternatively, round ruedas shaped like doughnuts can be cut into the grass when species or design dictates fewer trees per meter. Spacing of trees depends on species and steepness of grade or slope as well as long term goals whether growing lumber or food forest for future generations.
Areas with regenerating secondary forest can also be planted in order to increase biodiversity and attempt to re-grow the trees that were once present in the area prior to rampant deforestation. Again, it is not advisable that one enters and chops down everything present in order to “reforest”. A blank slate is not needed or desired. Swaths or carriles are cut and the surrounding vegetation is taken advantage of to shade delicate shade tolerant species. In Costa Rica, almost all of the rare tropical hardwoods require shade for optimal growth rates especially the first years.
Given that in Costa Rica there is an 8-month period of rain each year, sometimes very heavy, managing rainwater is an important issue to consider. Whether the terrain is steep or flat, water drainage is key to overall success of any project. Using trees and plants to act as natural living water barriers to slow down the rainwater and help the soil absorb better is not only attractive but also wonderfully useful. Artificial barriers of bamboo, hardwoods, brushwood, and other materials constructed in a grid or contour pattern, or grasses like vetiver and trees planted in a similar pattern, can be used to decrease velocity of running water especially in mountainous areas. Arranged in terrace format and running with the contour of the land, these natural dams help to slow and even stop water thereby decreasing soil run off and loss of nutrients. Construction of bench terraces on steeper slopes, and dividing water into numerous channels that run-off into smaller area keeps the impact from overflowing in any one area.
Minimizing your earthen run-off through conservation measures like those explained above is connected to the overall health of the area. This is more and more important due to the sheer numbers of people bulldozing land in the mountains. If you have ever seen the rivers running in Costa Rica looking like cafe con leche, (coffee with milk), this is an indication that people upstream are not properly controlling their erosion.
It may be necessary to add nutrients during land preparation. Several techniques exist including mulching with organic matter, planting nitrogen-fixing trees, applying green manure (especially herbaceous legumes), and commercial fertilizers. Mulching suppresses weeds, improves soil moisture conditions, and augments soil organic matter, but it may increase problems with rodents or other pests. Nitrogen-fixing trees can improve soil with their ability to produce nitrogen fertilizer. Foliage dropped by legumes is nitrogen-rich and will augment soil fertility as it decays. Other measures may also be used, such as the addition of small amounts of commercial fertilizers and amendments. Nutrient levels and fluxes in plantations should be monitored to determine the prospective benefits and cost effectiveness of soil amendments.
One of the less obvious soil deficiencies, occurring particularly in eroded soils in the drier climates is the lack of necessary micro-organisms. An ancient and effective method to add micro-organisms is to inoculate either nursery soils or planting holes in the field with a few grams of topsoil from well-established plantations or healthy forests. The method is not practical, however, where well-established plantations and/or healthy forests do not exist.
Species selection
Tree species selection is important to plantation success. If a tree is grown under unsuitable soil or site conditions, it will be stressed and thus become susceptible to attacks from insects or competition from weeds.
Sun or shade? Steep or Flat?
One of the easiest ways to insure that you are planting the appropriate species in the appropriate type of location is to ask whether there is full sun or shade and whether the land is flat or steep. This generally separates many species into categories. From here, one can determine if the species will tolerate degraded soil or rocky soil wet soil, or rather thrives along running water like a river or spring. In addition, while soil testing analysis can be conducted and special applications prepared to improve the quality of degraded soils, more sustainable and organic results can likewise be attained by planting nitrogen fixing, leguminous species that enrich the soil. This can be combined with other natural elements like calcium carbonate, a common white powder applied in summer months to assist plants in absorbing nutrients in the sulfur high acid content of some soils on the southern to Central Pacific coast of Costa Rica.
Several other factors influence species selection, including the objectives of reforestation, seed availability, and costs associated with reforestation alternatives. For many degraded sites, the species need to be those that can add nitrogen to the soil as well as provide food and products wanted by local communities. Creating biological corridors by planting fruiting and flowering trees in an interconnected fashion especially in protected zones around nacientes, streams and rivers ensures survival of species and plentiful food and water supply for all.
The importance of matching tree species with site cannot be over-stated. The problem of species selection is complicated in the tropics by intricate climatic and soil patterns and in areas that have been deforested by the highly variable degree of site degradation. Inadequate information on planting sites is a major cause of tree planting failure (Wadsworth 1982). With the wide range of altitudes common in Costa Rica, especially within any one farm, suitability and performance depends on selecting trees appropriate to your altitude level.
Since most tree species used in reforestation are found over broad geographic ranges, there are different land races (subdivisions of a species with heritable characteristics resulting from adaptation to a specific environmental condition). Tree species races are often described by referring to the geographic location where the race is found naturally. Thus, the species' suitability to a particular site varies depending on the races used. Increases in yield and resistances to disease can be achieved through selection and use of appropriate seeds. Only by planting species and races on the sites for which they are adapted can maximum yields be obtained.
Natives and exotics, monocultures ans polycultures
Not all “reforestation” is really Reforestation!
Plantations cannot substitute wholly for natural forests as reservoirs of germplasm or as components of the natural environment agricultural crop. Plantations contribute to preservation of the natural environment because they concentrate wood, food, and forage production within a minimum area, thus relieving some demands on natural forests. However, where plantations are established on land with good potential for annual agricultural crops, the effect actually may be to increase pressure on the natural forests.
Most large-scale tropical industrial timber plantations use species that are exotic to the planted area (Gallegos et al 1982). The widespread use of exotics may be a result of the preponderance of information, experience, and research on them, especially on Pinus, Eucalyptus, and Tectona. Also important to their use is the abundance, availability, ease of storage, and germination of seeds of these exotic species. The use of exotic tree species involves risks, such as susceptibility to pests and diseases. Moreover, exotic species like teak and eucalyptus can leach the soil of valuable nutrients thereby degrading it over the years and rendering it incapable of supporting other crops in future years without heavy commercial chemicals. Very little wildlife can subsist on a monoculture tree crop and these expanses of identical trees create barren areas in future years where the natural habitat has been destroyed. Because of the high yields possible with exotic species, however, the risks will continue to be taken.
The potential of using native species in plantations has been largely ignored. Reasons for this vary from lack of familiarity with many tropical tree species to lack of seed supplies. Native species are adapted to the local environment and, thus, may be less susceptible to stress, serious disease, and pest damage. Local people are more familiar with their native plants and have more uses for them. Forest plantations in the past usually served industrial purposes and grew only one product usually saw timber, pulpwood, or fuel wood. Now, with an increasing demand for food, fuel, and fodder, plantations are needed to serve a wider variety of objectives. Thus, the use of multipurpose trees and polycultural plantings (with many species of trees) is becoming increasingly important, especially in areas with high populations.
Planting materials
To reforest lands, seeds of various species must be available in great quantities. The seed supply for species most commonly used in tropical, industrial plantations is adequate. However, the seed supply for multipurpose, agroforestry species is small. The customary way of raising planting stock in the tropics is to grow seedlings in a forest nursery either in open beds for bare root planting or in containers. Good nursery practices are essential to produce a hardy plant with a well-balanced, straight root system. Bare rooted seedlings are susceptible to desiccation. Containerized seedlings are more costly and bulky to handle in the field and are subject to root coiling if closed-bottom containers are used. The latter can be avoided if the containers have an open bottom and are suspended above the ground.
Another technique for producing planting material is vegetative propagation Vegetative propagation is widely used for tree crops, such as rubber, coconut, tea, coffee, cocoa, and oil palm. Methods include cuttings, air layering, budding, grafting, and tissue culture. Rooted cuttings remain the most popular of these. Once the technique for a particular species is developed, the production cost is modest.
Vegetative propagation has the advantage of hastening massive reproduction of genetically superior plants, ensuring that all are of the desired genetic type. It has the disadvantage of increasing plantation risks due to lack of genetic diversity.
Seedling survival and growth rates in the nursery and at the planting site sometimes can be improved by using special kinds of fungi and bacteria. For most tropical trees, associations between tree roots and mycorrhizal fungi are essential for healthy growth. The fungi are active in the transport of nutrients and water to plant roots, and in some cases are important for the release of nutrient elements from mineral and organic soil particles. Trials have shown that seedlings inoculated with fungi show improved growth and survival over uninoculated controls. Populations of mycorrhizae are found naturally in soils, but these can be depressed after long-term clearing and/or topsoil removal, making reestablishment of vegetation on degraded lands difficult. Various methods for reinoculating damaged soils with mycorrhizal fungi are being developed.
Legume trees can grow well on degraded land because their roots can be a symbiotic host for Rhizobium bacteria which produce nitrogen fertilizer, an essential nutrient for plant growth. The bacteria convert nitrogen gas in the soil into a form the plant can use. Most soils contain Rhizobium, but degraded soils probably contain fewer types and lesser amounts of the bacteria. Thus, the appropriate type of Rhizobium may not be present at the site of a reforestation effort, or present in enough quantity to infect the tree roots.
Inoculants are living organisms that must be transported and stored carefully and used correctly to retain their viability. These requirements can be difficult to satisfy, especially at remote tropical sites needing reforestation.
An alternative to using seedlings in nurseries is to plant or sow the seed directly at the reforestation site. This method is feasible where seed is plentiful and where seed and seedlings mortality is low. Direct sowing of drought-resistant species is sometimes preferred, especially for species that have long and fast-growing taproots that may be damaged in a nursery or in transfer to the field. The advantage is that no nursery is required and planting costs are low. On the other hand, seedling survival may be low because of weed competition, lack of tending, poor weather, or animal damage.
Tree care and maintenance
Proper care and maintenance of the planted site is essential to ensure that trees survive to maturity. The first three to four years are labor intensive and subsequent management costs go down thereafter. If lumber is the focus, additional maintenance of trimming lower branches to produce Grade A wood without pockmarks augments costs.
Once grown, there is the problem of monitoring timber harvests and of systematic replanting. The main causes of reforestation failure, other than inappropriate technologies, are uncontrolled grazing and fires, competition from weeds, and uncontrolled cutting for fuel, fodder, poles, and lumber.
Direct protection through fencing or guards tends to be expensive. Other, less costly methods include planting unpalatable trees (e.g., Cassia siamea) or thorny trees, (e.g., Parkinsonia), as barriers around the plantation. The use of living fences is becoming a more widespread practice because they provide a number of auxiliary benefits including shade, fodder, windbreak, fuel, and wildlife habitat. Another alternative is subsidizing farmers with livestock feed or with cash to purchase feed during the period when trees are most susceptible to animal damage.
Grazing beneath the tree canopy sometimes can be beneficial as a means of weeding. However, livestock grazing on recently reforested watersheds can be harmful because animals compact the topsoil, leading to poor tree growth and increased runoff.
Weeding is an important aspect of plantation establishment and maintenance. Weeds compete directly with seedlings for light, soil nutrients, and water. Their shade can smother and eventually kill young trees. However, care must be taken in the Tropics, especially with native species, which almost always require some shading during the dry season with damaging sun. Therefore, it is recommended that weeding be limited to rainy season months and young trees not be disturbed in peak summer months.
There are three main methods of weeding. Manual cleaning with machete is the most common and requires capital to pay for local labor and administration. In many tropical countries, chemical weed control techniques have been tested and found successful, but because of safety and cost problems they seldom become the main means of weed control. Long term depletion of soil nutrients weighs thereby creating a dependency on subsequent application of commercial fertilizers heavily weighs against weed control through use of herbicides. Rainwater runoff of chemicals applied to plantations and reforestation sites further contaminates rivers and nacientes (e.g.; springs) and potentially harms wildlife and humans who later drink from natural water supplies.
Whatever the type and location of tree planting, the cooperation of local people is essential if newly planted trees are to survive. Because most trees do not yield much benefit for several years, the options offered must demonstrate explicit benefits to the people. Tree planting programs are most successful when local communities are involved and when the people perceive clearly that success is in their self-interest.
In local communities, support can be generated through local involvement in project design, demonstration plantings, and commercial plantings by entrepreneurs with larger land holdings, education of community leaders, extension and training programs working directly with farmers or laborers and direct financial assistance or provision of substitutes.
Successful reforestation requires sufficient funds, strong Political will, massive popular support, and cooperation among all involved parties. Foresters and policymakers must remember that "forestry is not, in essence, about trees. It is about people. It is only about trees so far as they serve the needs of the people." (Gribbin 1982).
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Deforestation
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