In the 1950s, Thailand became increasingly involved in international trade. One of its greatest resources was the northern teak forests. In an effort to balance international debt payments, Thailand increased exploitation of its forests. Logging, both legal and illegal, eliminated huge areas of forest. Between 1961 and 1988, forest cover was reduced from 53 to 28% of the total area of the country.
To remedy the problem of an inadequate supply of teak and the need for employment of landless peasants, a modified version of taungya was introduced in Thailand. Taungya is a land management system with origins in Burma (Myanmar). The British Colonial foresters encouraged peasant farmers to reforest logged areas with teak, allowing them to cultivate crops for the first few years among the teak seedlings. The system was resurrected in 1975 when the Cabinet of Ministers directed the Royal Forestry Department to reallocate land in degraded national forest reserves through the Forest Village System.
If a peasant family joins a Forest Village System they are allotted 1.6 ha of land each year. The land is to be cleared and planted with forest trees. Cultivation of crops such as upland rice is permitted between the tree seedlings. An additional 0.16 ha is given for a dwelling and home gardening. Water, electricity, education, and health care are provided. Two laborers from each family are recruited to work in plantation activities. This employment adds substantially to family income.
The Forest Village Systems have only been partially successful. While large areas of degraded land have been reforested with valuable timber species, the system is not without problems. Nutrient losses occur during the cropping period, but they are small compared to the total stocks in the ecosystem. These losses probably do not affect the growth of trees. However, nutrient loss due to clear-cut harvesting at the end of each rotation of teak can deplete stocks to levels insufficient to ensure satisfactory production during subsequent rotations.
Social and economic problems also occur within some taungya systems. A frequent source of discontent amongst the peasants is that they are unable to own property. Some villagers view their participation in the system as only temporary until they can somehow own their own land. This causes conflict with the system managers who would prefer the villagers to remain permanently. A nomadic tradition in some indigenous groups is also an obstacle to integrating them into taungya village systems. Other problems result from competition between trees and crops and the peasants not having strong incentive to ensure success of the tree plantation. They may have more interest in ensuring good crop growth from which they will derive personal benefit. Sometimes the peasants deliberately damage the plantation trees in order to favor the growth of crop species. Another problem in plantations of long-lived species such as teak is the long time interval during which there is no economic income from the land on which the trees are planted. An effort to remedy the problem is being tried in several of the forest villages. Fruit trees are interplanted among the timber species. The fruit trees begin to produce shortly after the cultivation of rice ceases and the economic production can help bridge the gap until the time that the timber trees are harvested. Fruit of trees such as tamarind (Tamarindus indica) are popular in the markets of Bangkok.
Agroforestry systems can be simultaneous when trees and crops or animals are in combination for the whole duration of the productive cycle. Some examples are permanent crops such as shade-grown coffee and cacao (Figs. 6.10 and 6.11), home gardens, alley-cropping systems, and agrosilvopastoral systems (combinations of trees with animals and pastures or agricultural crops). In alley cropping, annual crops are grown between hedgerows of leguminous nitrogen-fixing shrubs and trees, which are periodically pruned to prevent shading of companion crops. The prunings can then be used as mulch and green manure to improve soil fertility and produce high-quality fodder. Alley cropping is regarded as an improved bush-fallow system with the following potential advantages: (1) cropping and fallow phases are combined; (2) cropping periods are longer, and land is used more intensively; (3) soil fertility is effectively maintained with the use of species selected for that purpose; and (4) the need for external inputs is reduced (Kang and Wilson 1987).
Several studies have shown the ecological and economic advantages of combining nitrogen-fixing trees and timber or fruit trees with perennial crops such as coffee and cacao. For example, in Costa Rica, Beer (1988) compared the annual nutrient return in litter fall and prunings in systems of coffee with a nitrogen-fixing leguminous tree, Erythrina poeppigiana (poro), and a timber tree of good commercial value, Cordia alliodora (laurel). Both trees are common in agroforestry systems with perennial crops in Latin America. The amounts of nutrients recycled by the associated trees reached the recommended levels of fertilizer required for coffee production. The system including laurel was preferred by the farmers because of its timber value. Several other examples of combinations of trees and perennial crops have been described (Box 6.9). Their advantages are generally both ecological (the contribution of trees to sustain-ability of the systems) and economic (product diversification, more efficient use of land).
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