Silviculture and management of teak plantations

B. Krishnapillay

Baskaran Krishnapillay is Director of the Forest Plantation
Division, Forest Research Institute Malaysia (FRIM).

Management strategies and ecological requirements for enhanced growth and quality of plantation teak.

Although teak logs harvested from native forests, principally in India and Myanmar, are major contributors to the global timber trade as well as to domestic markets, the supply of forest logs from these countries is becoming progressively restricted. In Thailand, harvesting of teak, along with other native forest species, has been prohibited since 1989, while in the Lao People's Democratic Republic, supplies have been severely constrained pending a reassessment of harvest potentials. Thus in long-established and substantial markets for teak products, such as Thailand, Singapore and China, there is major concern regarding the future supply of teak.

Plantations are an important potential source of timber to narrow the growing gap between supply and demand for teak. This article looks at the potential of teak as a plantation species, focusing on management strategies, ecological requirements, growth performance, wood quality and availability of planting materials, with examples drawn particularly from the Malaysian experience. Finally, it enumerates some topics of current research likely to contribute to teak plantation development.

DEVELOPMENT OF TEAK PLANTATIONS

The durability and workability of teak were recognized many centuries ago, leading to its relatively widespread distribution and cultivation throughout the tropics. Today, teak ranks among the top five tropical hardwood species in terms of plantation area established worldwide (Table 1).

TABLE 1.Main tropical hardwood species in terms of plantation area, 1995

Source: D. Pandey, unpublished data.

In Myanmar, the area of teak plantations, the first of which may have been established about the year 1700, is estimated to be 139 000 ha,¹ making plantations an important supplement to supplies from native forests.

Establishment of plantations in India commenced in 1842. From that year until 1862, more than 1 million teak plants were raised for plantation development. The area planted is now about 980 000 ha.

Five-year-old teak plantation, Malaysia

- B. KRISHNAPILLAY

In Thailand, pioneer plantations of teak were established from 1906, and teak plantations currently cover approximately 159 000 ha. Thailand has a very heavy dependence on imports of plantation-grown teak for its rapidly growing export-oriented furniture manufacturing industry. This industry employs approximately 400 000 people, is responsible for export earnings of approximately US$400 million and since 1945, in conjunction with Scandinavian designs and manufacturing techniques, has done much to popularize teak furniture on a global basis.

Teak plantations in Indonesia are largely located in Java and currently exceed 700 000 ha. Teak was probably introduced into Java in the fourteenth century, although some reports suggest that its introduction may have been as early as the seventh century. Harvests from Javanese teak plantations today support a rapidly expanding furniture manufacturing industry, the products of which are increasingly directed to export markets. Production of teak occurs in two sectors: one is a free market and the other is controlled by a State enterprise company, Perum Perhutani. Perhutani's teak production and processing activities are well organized and extensive, involving the provision of planting stock, consumable inputs such as fertilizers, and specific advice to assist landholders with the establishment and management of their teak plantations. In return for these inputs, Perhutani is granted the rights to the logs harvested from the areas concerned.

Management of teak plantations in Java, Indonesia, is mostly controlled by Perum Perhutani, a State enterprise company, which assists forest farmers in return for the rights to the logs harvested from the areas concerned; here, Javanese forest workers cut and trim teak logs

- FAO/12605/M. PICKSTOCK

Cultivation of teak in Malaysia is a relatively new undertaking. The total areas planted in peninsular Malaysia and Sabah are estimated to be approximately 2 000 ha each (Asian Timber, 1996; Tee, 1995). Until recently, it was widely believed that teak grew best in the drier states in the north of peninsular Malaysia and it was not promoted in other parts of the country which are hotter and wetter. However, results from those areas now indicate that they are equally suited to the production of teak (see below), and this has generated considerable interest in the establishment of teak plantations on a large scale. The establishment of teak plantations in Malaysia is being actively promoted by the Department of Forestry, the Forest Research Institute Malaysia (FRIM), the Federal Land Development Authorities, other govern-ment agencies and the private sector. These commercial planting programmes aim to achieve mean annual increments of 8 m³ or more per hectare per year. Developments are occurring on an industrial plantation scale (>100 ha) as well as on smallholdings. Smallholder planting is being vigorously promoted as an enterprise requiring low labour inputs and offering potentially high returns.

Elsewhere in Asia, teak has been established in Bangladesh (~73 000 ha), Sri Lanka (~38 000 ha), China (~9 000 ha), the Philippines (~8 000 ha), the Lao People's Democratic Republic (~3 000 ha), Nepal (~2 000 ha) and Viet Nam (~1 500 ha).

In Africa, teak has been established in plantations in Nigeria (~70 000 ha), Côte d'Ivoire (~52 000 ha), Sierra Leone, the United Republic of Tanzania (~3 000 ha) and Togo (~4 500 ha). Plantations of teak are also widespread in the tropical Americas, where it was introduced early in the twentieth century. Teak plantations now cover an estimated 33 000 ha, spread mainly across Costa Rica, Trinidad and Tobago, Panama, El Salvador, Colombia, Guatemala, Venezuela and Ecuador.

In the Pacific region, teak was introduced by the Germans to Papua New Guinea in the early 1900s and some 3 500 ha of plantations were subsequently established. It was introduced to plantations in Fiji and the Solomon Islands. Teak has also been planted in northern Australia at trial levels.

Although it is widely planted, plantation-grown teak has not, until recently, had a significant impact on supplies of industrial roundwood in the global timber trade except for some short-term log exports from Papua New Guinea and Ecuador.

¹ The source for all plantation area figures in this section is FAO, unpublished data.

TEAK AS A PLANTATION SPECIES

Teak is relatively easily established in plantations and because of the enduring global demand for products from teak it has good prospects as a plantation species. These prospects are boosted by the rapidly developing trend of replacing lumber with reconstituted panels (Loke, 1996). Sliced veneer of teak as a lay-on for reconstituted panels is assured of a demand for its value in enhancing the potential for panels to substitute for lumber in a widening variety of applications.

Two major issues that affect the performance and management of teak plantations are the relatively low growth rates achieved and the desirability of maximizing the length of the clear bole so as to maximize the value of the log for high-quality end uses.

One-and-a-half-year- old teak plantation, Malaysia

- B. KRISHNAPILLAY

Growth rates

Modest growth rates are reported for teak plantations. Under favourable conditions in early life, a plantation may exhibit growth rates of between 10 and 20 m³ per hectare per year. However, growth falls to the general reported level of 4 to 8 m³ per hectare per year as the plantation ages (Htwe, 1999; Cao, 1999). On the best sites in Myanmar and India, 50-year-old plantations exhibit heights of 30 m and diameter at breast height (DBH) of 60 cm. Some growth parameters for teak grown in Malaysia are shown in Table 2.

TABLE 2. Performance of teak at Mata Air Station, Perlis, Malaysia

Long rotations in teak plantations appear essential if the high potential value of the heartwood is to be realized. Studies in India found that the heartwood content of 51- to 52-year-old trees was 77 percent, whereas for eight-year-old trees it was only 30 percent (Bhat, 1997). The same studies also showed a positive correlation of heartwood percentage with ring width (0.73) and with DBH (0.46), indicating that faster growth rates were associated with higher heartwood content and, by implication, higher-value timber. These results suggest that rotations longer than eight years are necessary for producing high-value logs and that faster growth rates may not be detrimental to the value of the timber.

Bole form

The phenomenon of fluting (irregular involutions and swellings) in the teak stem has been observed in a number of plantations. In an international provenance trial the mean heritability value of stem straightness was found to be 0.83, indicating that the character for stem straightness is strongly controlled by provenance and is thus genetically inherited (Kaosa-ard, 1999). Hence, fluting can be minimized if the appropriate provenance is used in breeding trials to produce plants that exhibit straight stems.

The most important form characteristic determining the value of teak logs is the length of the clear bole, which is determined by the timing of flowering. Flowering - representing the transition from production of vegetative structures only to the production of reproductive structures - occurs in response to certain environmental signals. Flowering by the terminal shoot is then immediately followed by the initiation of the whorl of branches. Selection for late flowering has been suggested as a means of maximizing the duration of the vegetative period, but this is usually in conflict with selection for early seed production. Therefore, management strategies as discussed below are generally employed to maximize the length of the clear bole.

MANAGEMENT STRATEGIES

Teak is an obligate light-demanding species throughout its life cycle. Inferior trees are readily suppressed if stand density is too high. Accordingly, plantations must be thinned regularly and heavily, particularly in the first half of the rotation. Initial planting density is generally between 1 200 and 1 600 plants per hectare.

The spacing of trees and the number, timing and intensity of thinnings strongly affect the pattern of growth and the yield of the plantation. If thinning is practised late, growth rates decline or cease, whereas if the stand is thinned too early or too heavily, the trees have a greater tendency to produce side branches and epicormic shoots. This also reduces the potential yield of the plantation since growth is diverted from the main stem, which should be free from defects such as those caused by side branches and epicormic shoots.

The timing of the first thinning is often determined by the height of the trees and is commonly carried out when the trees reach 9.0 to 9.5 m. The second thinning may be carried out when the trees reach 17 to 18 m.

The site generally has a carrying capacity independent of initial stocking rates and thinning regimes. The carrying capacity is measured in terms of the basal area (the average cross-sectional area of all trees per unit of land). It is possible to identify the thinning regime necessary to achieve a certain basal area on an area of land by retaining a minimum number of trees. The mean basal area is often allowed to reach 20 to 22 m² per hectare after the second thinning. A third thinning is then carried out to reduce the mean basal area to 13 to 15 m² per hectare. Thinning and pruning operations have a strong effect on the yield and quality of timber. To produce long boles free from knots, the usual strategy is to keep stands closed using high-density plantings, which remain untwined for the first three or four years of the plantation. The objective is to minimize the size of the crowns and the side branches in order to improve the quality and appearance of the timber and, thereby, its value.

Overall, it is desirable to thin the stand to the number that is optimal for reduction of undue competition and for the best growth of the remaining trees. A final stocking of about 300 trees per hectare would be the ideal.

ECOLOGICAL REQUIREMENTS

Soil requirements

Teak can grow on a variety of soils. The quality of its growth, however, depends on the depth, structure, porosity, drainage and moisture-holding capacity of the soil. It develops best on deep, well-drained and fertile soils, especially on volcanic substrata such as igneous and metamorphic soils or on alluvial soils of various origins. The optimal soil pH is between 6.5 and 7.5. The calcium content of the soil is also an important factor; calcium deficiency in the soil results in stunted growth of teak (Kaosa-ard, 1981).

Studies at FRIM indicate that good management techniques may be able to improve the performance of teak on problem soils (see Box).

TABLE 3. Growth of mature stands of teak on various soils, unmanaged

Source: Amir Husni (1998).

TABLE 4.Growth of young teak stands on various soils under plantation management regime

Source: FRIM, unpublished.
Note: The source of all seeds was FRIM, Perlis, Malaysia.

Temperature and rainfall

Teak grows best when the minimum monthly temperature is above 13^oC and the maximum monthly temperature is below 40^oC. Optimal rainfall for teak ranges between 1 250 and 3 750 mm per year; however, for the production of good-quality timber the species requires a dry season of at least four months with less than 60 mm precipitation (Kaosa-ard, 1981).

In Malaysia, various small plot studies in Perak (rainfall 2 800 mm), Selangor (rainfall 2 500 mm), Kepong (rainfall 2 600 mm) and Johore (rainfall 2 700 mm) over the past three to five years have shown that teak can thrive equally well, if not better, in regions that are wetter and hotter than those where it has usually been grown. The early growth performance of the trees in these wetter, hotter regions has been remarkable and has sparked interest in promoting teak on a large scale in Malaysia.

A report from India (Kondas, 1995) shows that teak responds very well in terms of growth and girth increment in areas where the trees receive at least sufficient moisture for most of the year when compared with growth in monsoon areas.

There is a misconception that annual growth rings, which impart grain structure to the logs, occur only in teak trees growing in zones that have distinct rainy and dry seasons and not in those growing in regions where rainfall is received year round. It is probable that trees grown in zones with a long dry period will have very distinct, closely packed concentric rings owing to the inactivity of the cambium during the long dry spell. However, the growth ring continues to be formed in all climatic conditions, even where there is year-round high rainfall.

QUALITY OF PLANTATION-GROWN TEAK

It has been alleged that teak obtained from plantations is of inferior physical quality relative to teak obtained from the natural forest. More variability in wood quality has been observed in teak obtained from the natural forest than in plantation teak, and this is undesirable from the point of view of use. The general notion prevailing among teak users is that fast-growing teak produces only light, weak and spongy wood (Bryce, 1966). However, studies conducted at the Forest Research Institute in Dehra Dun, India, do not support this view. Although plantation trees grow faster than forest trees, it has been shown that the relationship between growth rate and strength is not significant (Sekar, 1972).

Studies by Sanwo (1986) based on dominant, co-dominant and subdominant trees from a 27-year-old teak plantation in Nigeria showed that the rate of growth has no significant influence on specific gravity. Teak wood is generally stronger at the upper and lower ends and comparatively weak at intermediate heights. A study on 20-year-old teak trees grown in plantations in wet areas in India gave similar results (Kondas, 1995).

Other studies have indicated that wood density and mechanical properties are independent of growth rate or that fast-grown trees of ring-porous species have higher wood density and strength (Harris, 1981; Bhat, Bhat and Dhamodaran, 1987; Rajput, Shukla and Lai, 1991). More recently, a study on the wood properties of fast-grown plantation teak trees of different ages revealed that there were no significant differences in wood density, modulus of rupture (MOR), modulus of elasticity (MOE) or maximum crushing stress (Bhat, 1998). It was concluded that young trees (13 to 21 years of age) are not necessarily inferior in wood density and strength to older trees aged 55 and 65 years, and hence that the rotation age of fast-grown teak wood can be reduced without affecting the timber strength.

Various products such as glue-edged boards, furniture, doors and small teakwood artefacts have been made from thinning materials, showing that even sapwood can be used to produce high-quality objects.

AVAILABILITY OF PLANTING MATERIALS

Teak plants can be raised using either seeds or vegetative tissues (stumps, branch cuttings etc.). Plants raised from seeds collected at random tend to show fairly wide variability in growth, while vegetative propagation using cuttings and tissue culture ensures production of uniform planting materials of desired qualities. However, seeds are very important to maintain a broad genetic base. To obtain fairly uniform planting materials from seeds, seedling or clonal seed orchards of good-quality trees have to be raised for seed collection.

The large variation in growth conditions within the natural range of teak suggests that there is a likelihood of substantial genetic variability among provenances. Furthermore, the long-term cultivation of teak in regions outside its endemic area (e.g. in Java, Indonesia) suggests the possible existence of land races that are specifically adapted to the regions to which teak has been introduced.

To examine these questions, an international series of provenance trials was established (Keiding, Wellendorf and Lauridsen, 1986; Kjaer, Lauridsen and Wellendorf, 1995; Kjaer and Foster, 1996). These trials showed that, in general, local seed sources should be preferred when teak is established within the area of its natural distribution (White, 1991). Although local sources did not always give the fastest growth rates, they consistently gave good performance relative to seedlots introduced from elsewhere.

In contrast, for regions outside the natural range of teak, local seedlots were sometimes very poor for some characters of commercial significance and were thus unsuitable for use in developing commercial-scale plantations. Of particular interest, however, was the broad adaptation of provenances from southern India and Indonesia, which exhibited good survival, growth rates and form.

At present, planting material of the desired quality and of known genetic source is not available in sufficient quantity. There is significant demand for good-quality planting stock for plantation programmes not only in Malaysia, but also in the Philippines, Viet Nam, Thailand, Myanmar, Indonesia and India.

Plant stocks currently being used for the Malaysian plantation programmes principally originate from local unidentified sources or from Thailand. There is no accreditation to ensure that the material comes from a reliable source of good-quality germplasm or, indeed, from the source named by the supplier. This presents a risk for plantation managers. FRIM is currently working with some reliable commercial nurseries and plant propagators to produce large enough quantities of high-quality plants to meet Malaysia's needs.

RESEARCH CONCERNING TEAK PLANTATIONS

Teak has been the subject of comprehensive research programmes in India, Indonesia, Thailand and Myanmar for at least 50 years. Some of the key outcomes from those programmes with respect to plantations have been the identification of élite genetic material for wide-scale planting and the development of silvicultural practices that optimize the production of high-grade timber.

In Malaysia, FRIM is currently undertaking research on the following areas to enhance teak plantation development:

• tree improvement, with the establishment of seed and clonal orchards to make available élite
  planting materials for mass multiplication;
  
• tissue culture, to develop large-scale in vitro propagation techniques for the production of uniform true-to-type plants for the plantation industry;
  
• genetic evaluation and fingerprinting of teak clones using isoenzyme and molecular markers;
  
• species site matching, with on-going detailed studies;
  
• optimum thinning regimes, fertilizer requirements and sound silvicultural practices, through planting trials.
  

CONCLUSION

Teak has fairly good growth rates and the return from the species is lucrative enough for exploitation on a commercial basis. It is thus suitable as a plantation timber species in areas with ecological conditions appropriate for its growth, and it appears to have potential for use in the Forest Plantation Programme in Malaysia. Preliminary experiences indicate that teak can grow on a wide variety of soil types in Malaysia; however, on problematic soils there is a definite need to use intensive silvicultural management practices. 

Bibliography

Amir Husni. 1998. The preliminary performance of teak crop when planted on various soil types in peninsular Malaysia. Paper presented at the Malaysian Science and Technology Congress, Kuala Trengganu, Malaysia.

Asian Timber. 1996. First teak plantation for Sarawak. (July): 12.

Bhat, K.M. 1997. Characterization of juvenile wood in tropical hardwood teak. Paper presented at the Conference on Forest Products for Sustainable Forestry, Pullman, Washington, USA, 7-12 July.

Bhat, K.M. 1998. Properties of fast-grown teakwood: impact on end-users' requirements. Journal of Tropical Forest Products, 4(1): 1-10.

Bhat, K.M., Bhat, K.V. & Dhamodaran, T.K. 1987. A note on specific gravity difference between dominant and suppressed trees in teak. Indian Journal of Forestry, 10(1): 61-62.

Bryce, J.M. 1966. Mechanical properties of Tanzania-grown teak. Technical Note No. 34. School of Forestry Division, Moshi, United Republic of Tanzania.

Cao, Q.N. 1999. The process of establishment of teak (Tectona grandis) plantations in Vietnam and the results obtained. Paper presented at the Regional Seminar on Site, Technology and Productivity of Teak Plantations, Chiang Mai, Thailand, 25-29 January.

Harris, J.M. 1981 Effect of rapid growth on wood processing. In Proceedings of the XVII IUFRO World Congress, Kyoto, Japan, 6-12 September 1981, p. 117-125.

Htwe, U.M.M. 1999. Teak plantations in Myanmar. Paper presented at the Regional Seminar on Site, Technology and Productivity of Teak Plantations, Chiang Mai, Thailand, 25-29 January.

Kaosa-ard, A. 1981. Teak (Tectona grandis L.f.) - its natural distribution and related factors. Natural History Bulletin of the Siam Society, 19: 55-74.

Kaosa-ard, A. 1999. Gain from provenance selection. Paper presented at the Regional Seminar on Site, Technology and Productivity of Teak Plantations, Chiang Mai, Thailand, 25-29 January.

Keiding, H., Wellendorf, H. & Lauridsen, E.B. 1986. Evaluation of an international series of teak provenance trials. Humlebaek, Denmark, Danish Inter-national Development Agency (DANIDA) Forest Seed Centre.

Kjaer, E.D. & Foster, G.S. 1996. The economics of tree improvement of teak (Tectona grandis L.). Humlebaek, Denmark, DANIDA Forest Seed Centre.

Kjaer, E.D., Lauridsen, E.B. & Wellendorf, H. 1995. Second evaluation of an international series of teak provenance trials. Humlebaek, Denmark, DANIDA Forest Seed Centre.

Kondas, S. 1995. Teak - a paragon of excellence. Malayan Forester, 38(4):111-125.

Loke, S.W. 1996. Malaysian timber industry gears up for 21st century. Asian Timber, (October): 20-26.

Rajput, S.S., Shukla, N.K. & Lai, M. 1991. Some studies on the variation of strength properties of Tectona grandis from Mizoram. Journal of Timber Development Association of India, 37(2): 33-38.

Sanwo, S.K. 1986. The relationship between rate of growth and strength in plantation grown teak (Tectona grandis L.f.). Journal of Tropical Forest Resources, 2: 9-17.

Sekar, A.C. 1972. A comparative study of strength properties of timber from natural and man-made forests. In Proceedings of the Symposium on Man-Made Forest in India, Dehra Dun, India, 5: 29-32.

Tee, B. 1995. Teak in Sabah. A sustainable agroforestry - the Haris Salleh experience. Kota Kinabalu, Malaysia, Sejati Sd. Bhd.

White, K.J. 1991. Teak - some aspects of research and development. RAPA 1991/17. Bangkok, Thailand, FAO Regional Office for Asia and the Pacific.