Emerging Markets / November 1, 2018

Applied Silviculture, Maintaining a Teak Plantation

The self-managing nature of a forest is one of its most attractive qualities. Mature trees spread far and wide to soak up sunlight. Younger saplings establish themselves below, waiting for a window of opportunity to make a break for the canopy. Vines wind up trunks, and brush and groundcover soak up whatever light makes it to the forest floor.

Applied Silviculture, Maintaining a Teak Plantation

At first glance, it would seem agroforestry would be as simple as plant and wait, but as the Center for International Forestry Research explains, when producing hardwoods for market, such a “laissez-faire cultivation practice” limits productivity and quality. Bringing the highest quality timber to market requires careful attention and silvicultural treatment.

Silviculture is the practice of controlling the establishment, growth, composition, health, and quality of forests. Specific practices are guided by the goal of the forest system. When producing hardwood lumber, the most desirable attributes include straight, thick trunks that are free of branches and knots, maintain a smooth wood grain and fiber, and have minimal wood defects, such as knots or insect damage.

Achieving these results starts from the ground up. The best seed will come from the best trees. Sourcing seeds from un-diseased trees with straight stems, long boles, and healthy crowns will lead to increasingly superior yields down the road. Teak seeds have a strong seed coat, and can be difficult to germinate, but with proper soaking and scarification (soaking seeds in acid to replicate the effect of passing through an animal digestive system) a nursery can be quickly established.

Germinated seeds are typically transplanted to growing bags within a week of germination. There they establish a strong root system and stem before being moved into the plantation. Uniformly spacing the plantation allows trees to establish without self-competing for light, water, and soil nutrients. Proper spacing also allows for good air circulation while minimizing wind damage.

Fertilization is critical in the first three years as young trees establish themselves. At this point, weeding is also a must to encourage sapling development. Understory brush and weeds compete for resources, inhibiting teak growth. As the trees mature, weeding becomes less necessary because older trees will outcompete weeds on their own.

While young, trees are planted densely. Close initial proximity forces young trees to invest in rapid vertical growth towards abundant sunlight. Once straight trunk growth is established, the stand density will be thinned to encourage wider trunk diameters. Thinning takes place about every 3-4 years until trees reach the age of 15, at which point the stand needs thinning every 5-10 years. Thinning out diseased trees, or those with poor form, keeps the stand healthy and ensures top timber quality. Infilling of dead or diseased trees with new starts can be done periodically during the rainy season to keep stand density uniform.

Regular pruning of lower branches increases the length of clear bole and allows the tree to focus on trunk and canopy development. Pruning should never exceed 50% of the foliage, as over pruning will limit photosynthesis and in turn, future growth. Pruning typically begins in the third year, at which point young trees are ready to manage the stress of foliage removal. Branches should be pruned as close to the trunk as possible without damaging the branch collar (the slight swelling around the base of the limb) in order to minimize knot formation and the opening of wounds that could potentially infect the tree.

Ongoing maintenance includes management of insect and disease infestation to ensure wood is of the best quality when ready to harvest. When implemented correctly, silvicultural management produces healthy trees exhibiting the most desirable traits.

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