BURMA TEAK: THE MANAGEMENT OF TEAK

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Subject: Re: BURMA TEAK:  THE MANAGEMENT OF TEAK PLANTATIONS

Re Burma Teak,we regret the use of the euphemism 'Mynamar', it is not
ours,  metta, dawn star


Julio Cesar Centeno wrote:
> 
> *
>                         THE MANAGEMENT OF TEAK PLANTATIONS
> 
>                                        Julio César Centeno
> 
> _______________________________
> NOTE: A complete version of this article may be found in the
> ITTO Tropical Forest Update, Volume 7, No. 2, 1997,
> or at the following web page:
> http://www.ciens.ula.ve/~jcenteno
> ________________________________
> 
> Teak [Tectona grandis L] is a tree originally from an area encompassing
> parts of India, Thailand, Myanmar and Laos. It seems to have been
> introduced to Java, Indonesia, in the 14th century. There are references
> to plantations established in India in the early 1800s, and in tropical
> America about 100 years later.
> 
> Although it is not devoid of silvicultural and management difficulties,
> it is a well-known timber species, which has performed well in
> plantations not only in its Southeast Asian range of origin, but also in
> other parts of Asia, as well as in Africa and Latin America.
> 
> The total area under teak plantations today is estimated at 3 million
> hectares (1). Good growth and high quality is associated with deep,
> flat, and well-drained alluvial soils, rich in calcium; a mean annual
> temperature between 22 and 27 degrees centigrade; and an annual
> precipitation from 1,500 to 2,500 millimeters, with a marked dry season
> of 3 to 5 months with a maximum of 50 millimeters of rain.
> 
> Dry site conditions are usually associated with stunted growth. Very
> moist conditions may lead to faster growth, but also to a thick sapwood
> and poor overall quality, including lower average density, less
> attractive color, poor texture, and loss of strength.
> 
> Growth Patterns
> 
> The rate of growth and the quality of teak from plantations are largely
> dependent on the type and quality of the seeds; the physical and
> chemical characteristics of the soil, including topography and drainage;
> on environmental variables such as rainfall, temperature and humidity;
> and on management techniques.
> 
> Although a significant variety of growth patterns have been recorded in
> different part of the world, the best managed and most productive
> plantations tend to fall within a well defined range [Figure 1].
> Nevertheless, there are many cases of poorly established and managed
> plantations, with rates of growth below the lower estimate indicated in
> this figure.
> 
> Figure 1: Yield Potential of Teak Plantations
> 
> Teak trees grown in plantations on good soils may reach an average of 60
> centimeters of diameter at breast height [DBH], and 30 meters in height
> in about 50 years. In comparison, the largest standing teak tree,
> located in the Baw Forest Reserve of Myanmar, measured 2.4 meters in
> diameter and 46 meters high in April of 1996 (2).
> 
> Establishment Phase
> 
> Teak establishes best on terrain cleared of competing vegetation. An
> important aspect of plant competition may be sought in the relatively
> large need for aeration of the root system, and in the species
> requirements for light and nutrients. Like pioneer species, teak is
> unable to stand much competition from other plants, or from trees of the
> same species.
> 
> A viable option for the production of high volumes of quality teakwood
> is to establish pure plantations on well-prepared and well drained
> soils, and to manage them to reach a good average height before
> flowering sets in, making branching more profuse.
> 
> Spacing should promote rapid development of the saplings. The usual
> 1,200 to 1,600 plants per hectare is a good range, with closure of the
> canopy commonly taking place between the third and fourth year,
> suppressing the development of weeds.
> 
> A larger number of trees may be considered desirable to close the canopy
> quickly, to decrease the problems caused by weeds and the size of
> lateral branches, while forcing the live crowns high up along the stems
> in a shorter time. An early first thinning would then become necessary
> to prevent stunting, while keeping a large enough basic stock on which
> to mold a good final crop.
> 
> Pure stands have been associated with the deterioration of the soil and
> erosion. However, there is limited conclusive evidence in this regard,
> except when teak is planted on steep slopes; where undergrowth has been
> systematically cleared; or where excessive burning has taken place. The
> management of pure stands where a protective understorey is maintained
> after canopy closure, tends to avoid the deterioration of the soil,
> particularly when the undergrowth contributes to the fixation of
> nitrogen.
> 
> Pure teak plantations are often prone to attack by defoliators,
> especially when planted on unsuitable soils, poor in nutrients. On the
> best sites, where healthy growth is present, attack by defoliators is
> less frequent and intense, and can be further reduced with the
> maintenance of a suitable understorey.
> 
> Stand Dynamics
> 
> A series of options are available to influence the development of a
> plantation, as well as the quality and quantity of the timber produced.
> Among these options is the space made available to each tree, which
> strongly influences its patterns of growth, and therefore the overall
> yield of the plantation.
> 
> The initial spacing of planting, coupled with the number, timing, and
> intensity of thinnings, largely determine the space made available to
> individual trees as they develop. These are fundamental decisions, with
> a profound effect on production.
> 
> Trees within a stand also interact and compete with each other, with
> reactions controlled mainly by their genetic base, and by the space,
> nutrients and light available to each. This generates a dynamic within
> the stand, which can be influenced by management decisions to achieve
> desired production objectives.
> 
> Within determined limits of thinning, where only small and temporary
> canopy gaps are created, total production should not deviate
> significantly from the carrying capacity of the site. If thinning is
> practiced late, the stand is affected by stagnation, with the loss of
> growth potential. If, on the other hand, the stand is thinned too early
> or too strongly, the trees tend to produce more side branches and
> epicormic shoots. This also implies a loss of growth potential, since
> the purpose is to produce as much timber in the main stem as possible,
> preferably free of knots and defects.
> 
> Epicormic shoots may also be related to the genetic imprint of the
> seeds. Erosion is a further threat when thinning is too strong.
> 
> Often the age at which the first thinning is practiced is determined by
> the dominant height, which in turn is determined by site quality.
> Dominant height is the average height of the 100 largest diameter trees
> per hectare. It may also be estimated from the average height of the
> five largest diameter trees in permanent sample plots, when these are of
> 0.05 hectares in size.
> 
> As a general rule, teak should be planted only on the best site classes,
> with the first thinning taking place when the dominant height reaches 9
> to 9.5 meters, and the second when the dominant height reaches 17 to 18
> meters.
> 
> Each site has a certain carrying capacity, measured in terms of basal
> area [the average cross-sectional area of all trees per unit of stand
> surface]. The dominant height and the cumulative basal area are
> parameters normally not affected by either the initial stocking nor by
> thinning regimes. The thinning regime may thus be designed to
> concentrate the basal area carrying potential of the site in a minimum
> number of trees.
> 
> A guiding rule is to allow the mean basal area to build up to between 20
> and 22 square meters per hectare after the second thinning, and then
> thin the stand again to bring the mean basal area proportionately down
> to between 13 and 15 M2 per hectare.
> 
> The combination of reliable information on dominant height and
> cumulative basal area provides one of the best approaches to the
> successful management of teak plantation in tropical environments.
> 
> Thinning and Pruning
> 
> Thinning and pruning operations are closely inter-related, with a strong
> influence on the quality of the wood and on production performance.
> Thinning regimes are dictated by the development of the trees in height
> and basal area. Theoretically, the amount of all wood formed per hectare
> will be more or less the same for stands of the same provenance, age and
> site quality, but varying in numbers of trees, as long as the canopy
> remains closed. How much wood goes into the branches of the crown, and
> how much goes into the valuable part of the stem, depends largely on the
> thinning schedule.
> 
> A common strategy to grow long boles, clear of knots, is to keep the
> stand quite closed and high in number of trees during the first years of
> development, when rapid height growth occurs. This is meant to keep
> crowns small, and consequently limit the size of the branches.
> 
> Knot free timber is desired to improve the quality and appearance of
> high-grade construction material, furniture, decorative veneer and
> plywood, among other uses. It is also desirable to improve the working
> properties of the timber, to facilitate peeling, finishing, and
> seasoning, and for the uniformity of strength.
> 
> The management strategy can be designed to encourage the formation of
> clear boles, by pruning the trees that will yield commercial timber,
> while keeping the stand low in the number of stems. The trees then must
> have larger individual crowns to keep the canopy closed, and the wood
> volume produced will be concentrated on lower numbers of trees, which
> thus will be thicker than in stands with higher numbers.
> 
> Even within a tree species, there may exist various provenances with
> genetic predisposition for small or broad crowns. The thinning schedule
> has thus to be adapted to the provenance used, and improved through
> experience and experimentation.
> 
> The removal of branches up to a desired height is done first near the
> time of canopy closure. Pruning also serves to reduce the chances of
> ground fires reaching the crowns, and to facilitate access to the stand.
> It is a costly operation, which should be perceived as an investment to
> improve the quality of the final product. As much self-pruning as
> possible should be provoked through stand architecture. Since both the
> demand and the price for high quality tropical timber tend to increase,
> pruning becomes an attractive silvicultural operation and a fruitful
> investment.
> 
> For cost effectiveness, pruning should be done selectively, coordinated
> with the intended method of thinning, clearing 2 to 3 meters of stem at
> a time.
> 
> Nevertheless, teak has the propensity to produce adventitious branches
> and epicormic shoots next to the scars caused by pruning. To prevent
> their development, pruning should be carried out just after the period
> when most new leaves are produced. To minimize damage, it is better to
> sever the branch about 30 cm from its connection with the stem, before
> cutting the stub flush with the trunk of the tree, using a pruning saw.
> This prevents the branch from breaking when the saw cut is nearly
> complete, tearing a strip of bark from the stem as it falls.
> 
> A balance is necessary between the need to produce knot free timber, the
> stem length pruned at a time, and the need to prevent a slowing down of
> growth due to an excessive reduction of the crown.
> 
> Rotation
> 
> Based on a weighed assessment of economic and silvicultural
> considerations, a rotation of 25 years to 40 years may at present be
> considered as the optimum cycle to achieve a viable balance between
> financial returns and the production of market quality timber. During
> this rotation period, thinning operations will provide returns at
> intermediate stages, easing the economic burden related to the long-term
> nature of the operation, and making the investment financially
> attractive.
> 
> In Asia, teak trees are often allowed to develop for 60 years or more
> before harvesting. At such ages, the mean annual increments may vary
> from 3 to 10 cubic meters per hectare per year. Most plantations in
> tropical America are managed with far shorter rotations, usually from 20
> to 30 years. The mean annual increment at such ages may vary from 10 to
> 20 cubic meters per hectare. This does not mean teak grows better or
> faster in America. Were these plantations allowed to develop for 60 or
> 80 years, they would register similar mean annual increments as those in
> Asia for the same age.
> 
> References
> 
> 1. Own estimate based on a) FAO Forestry Paper 128: Tropical Forest
> Plantation Resources, 1995. b) TEAKNET Second Regional Seminar on Teak,
> Yangon, Myanmar, 1995. c) Pandey: Assessment of Tropical Forest
> Plantation Resource, 1992. d) Own collection of statistics between 1990
> and 1996 for tropical America.
> 2. Myanmar Forest Service: Myanmar's Mighty Teak Tree, 1996.
> 
> _______________________________________________
> Julio Cesar Centeno, PhD
> Las Tapias, Edif. Carreto
> Pent House                              Tel. +58-74-714576
> PO Box 750                             Fax +58-74-714576
> Merida - Venezuela            Email: JCenteno@xxxxxxxxxxxx
> http://www.ciens.ula.ve/~jcenteno/
> _______________________________________________