Teak is one of the pre-eminent timbers of the tropics. It is highly durable, easily worked, attractive, strong and relatively light. As the climatic and edaphic conditions in the south are suitable for teak, Vietnam has high prospects in teak wood.
I. CONDITION AND MANAGEMENT OF TEAK RESOURCES
Vietnam does not have any natural teak forests; thus, all teak resources originate from man-made forests. The current area of teak plantations is shown in Table 1 by age class.
- Growth rate and quality of teak plantations
The growth rate and quality of teak trees greatly differs according to the soil types and other associated characteristics. The main soil types in teak plantations are:
1) basaltic soil originating from volcanic rocks, which is very fertile and moist with good drainage;
2) ancient alluvial soil, which is deep and has sandy loam structure, usually being covered by shrubby trees and grasses; and
3) ferralitic soil, which is thin, of low fertility, has poor drainage, and is severely affected by drought in the dry season. Using these characteristics, the soils are classified as good, medium and poor sites for teak planting respectively. The growth rate on these three types of sites are shown in Table 2.
Table 1. Teak plantation areas by age classes in Vietnam
|Age class (years old)||Area (ha)|
|1 – 4||180|
|5 – 10||650|
|20 – 30||1,080|
|30 – 40||122|
Table 2. Average annual growth rate over 20 years in above soil types
|Soil Type (site quality)||% in occurrence||Spacing (m)||MAI|
|DBH (cm)||Height (m)||Vol.* (m3/ha)|
|Basaltic soil (Good site)||15||2.5 × 3.0||1.2||1.1||11.5|
|Ancient alluvial soil (Medium site)||45||2.0 × 3.0||0.9||1.0||8.5|
|Ferralitic soil (Poor site)||40||1.5 × 3.0||0.6||0.7||4.0|
Note: MAI = mean annual increment; DBH = diameter breast height; * = over bark.
On good and medium soil, the average ratio of healthy and well formed trees comprises 60-65% in plantations. On poor soil, the average ratio of badly formed and crooked trees rises to over 60%.
II. MANAGEMENT OF TEAK PLANTATIONS
Until recently, little attention was paid to teak plantings due to the following:
- Teak plantations were only successful in limited areas of some provinces in the eastern, southern and highland regions.
- Wood of indigenous species of the natural forest was preferred to teak.
- Local forestry enterprises preferred planting pulp wood species with short rotations to achieve early cash returns.
- Lack of knowledge about the processing and utilisation of teak wood and of its price on the international market.
Teak plantations on good and medium soil categories are established by the agro-forestry method.
As a consequence, they are well looked after for many years after planting, and forest fires rarely happen. On good soils teak is raised with crops such as green bean, soya bean, maize, dry land rice, etc., until the seventh year; on medium soils teak is planted more closely so that intercropping is possible only up to the third year. Due to the lack of funds, and as there is no market for small, thin logs, thinning operations tend to be delayed in both sites until the tenth year. In thinning operations, poor growing, badly formed and diseased trees are felled. It is considered that 2-3 thinnings would be needed until the final cut after 40-50 years. Produce is expected to be utilised in high value end products, quality furniture, and housing decorations.
Teak plantations on poor soil are treated in two different ways. First, plantations that have less risks of forest fires and less conflicts with local people can get more funds for protection and tending. Though the cutting rotations will become longer, the plantations are expected to supply high value produce. Second, plantations that are under a high human population pressure and are subjected to frequent bush fires and land trespass, as well as poor growth, are to be replaced with other tree species.
Thinning schedules have been prepared for large-scale plantations. Their operational guidelines are shown in Table 3.
Table 3. Trees remaining after thinnings on three site categories
|Thinning||Age (yrs.)||Number of trees after thinning|
* Site soil category
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