Silviculture and Important Tree Species

What to remember

• Silviculture is the art and science of growing and tending forest crops. Its tools are regeneration, tending (weeding, cleaning, thinning, pruning) and harvesting under a chosen silvicultural system.
• Species know-how decides exam marks. Teak needs deep, well-drained soil; sandal is a root hemiparasite needing a host; red sanders (Pterocarpus santalinus) is endemic to the Eastern Ghats of southern Andhra Pradesh; Casuarina fixes nitrogen with Frankia and grows on coastal sand.
• Bamboos are giant grasses. Most flower once in a very long cycle, then die (monocarpic), and flowering is often gregarious.

Basic silvicultural terms

• Silviculture: growing forest crops; silvics is the study of the life history and ecology of trees.
• Shade bearer (tolerant): grows under shade (for example silver fir, Mesua ferrea, Hopea); light demander: needs full light (teak, sandal needs partial shade when young, Eucalyptus, Casuarina).
• High forest: trees of seed origin; coppice forest: shoots from stumps or roots.
• Rotation: planned number of years between establishment and final felling of a crop.
• Site quality: productive capacity of a site, shown by height at a standard age.
• Rootstock/stump planting: a seedling cut to a short shoot and a few cm of root and planted (teak stumps).
• Girdling: cutting a ring of bark and sapwood to kill a tree slowly and season it standing.
• Pollarding: cutting the stem at about 2 m so shoots grow above grazing height; lopping: removing branches; pruning: removing branches to improve timber quality.

Silvicultural systems

Thinning removes some trees from a young stand to give the rest more room. Types: low thinning (removes suppressed and lower trees), crown thinning (removes dominants competing with good trees), mechanical thinning (fixed pattern, such as every third row), free thinning (combines methods). Cleaning removes unwanted species in sapling stage; weeding removes herbs and climbers; climber cutting is routine in natural forests.

Nursery and planting basics: raise seedlings in a nursery in beds or containers (root trainers, polybags); harden before planting; pit planting at the start of the monsoon; spacing depends on species and purpose. Seed pretreatment breaks dormancy: soaking in water, hot water for hard-coated legumes, scarification, or alternate wetting and drying for teak.

Teak (Tectona grandis)

• Family: Lamiaceae (earlier placed in Verbenaceae). Deciduous, tall tree of moist and dry deciduous forests.
• Soil and climate: best on deep, well-drained, fertile alluvial or loamy soil; will not tolerate waterlogging or very shallow soil. Needs a dry season for good timber.
• Light: strong light demander.
• Regeneration: natural regeneration is poor; plantations are made by seeds, stumps (a standard method), tissue culture or clonal planting. Seed has a hard, corky coat and low germination; alternate wetting and drying improves it.
• Spacing: commonly 2 m × 2 m or 3 m × 3 m for timber with thinning later.
• Timber: strong, durable, termite-resistant, good for furniture, ships and doors.
• Pests and diseases: teak defoliator (Hyblaea puera) eats leaves; teak skeletonizer (Eutectona machaeralis) eats leaf tissue between veins; heart rot (Phellinus/Fomes) in old trees.

Sandal (Santalum album)

• Family: Santalaceae. Small evergreen tree; root hemiparasite that sends haustoria to a host's roots for water and minerals; it makes its own food by photosynthesis.
• Hosts: a good primary host (for example red gram, Cajanus cajan) in the nursery and permanent secondary hosts (such as Casuarina, Cassia siamea, Pongamia) in the field.
• Product: the heartwood has the fragrant oil (chief constituent santalol); sapwood has no oil. Oil is used in perfumes and medicine; wood in carving.
• Soil: well-drained red loam, light shade when young.
• Disease: spike disease, caused by a phytoplasma and spread by insect vectors, makes leaves small, narrow and stiff and stops flowering; no cure, so affected trees are uprooted.
• Seed dispersal: birds spread seeds; direct sowing in the field and nursery transplants are both used.
• Law: sandalwood is a state-regulated produce; felling and transport follow forest rules.

Red sanders (Pterocarpus santalinus)

• Family: Fabaceae. Called red sandalwood, endemic to a small area of the Eastern Ghats in southern Andhra Pradesh (hills such as Seshachalam and Lankamalleswara, in the Kadapa, Chittoor and Nellore region).
• Features: small to medium deciduous tree; slow-growing; prefers dry, rocky, red, gravelly soil in hot dry climates.
• Product: heartwood is deep red; santalin is the colour pigment. Used for dye, furniture, carving and traditional medicine; it is not a fragrant sandalwood and has no relationship to Santalum.
• Conservation: listed in CITES Appendix II and regulated in trade; illegal felling and smuggling are a serious problem.

Casuarina (Casuarina equisetifolia)

• Family: Casuarinaceae. Evergreen tree with jointed, needle-like green branchlets; leaves are reduced to scales.
• Nitrogen fixation: root nodules with the actinomycete Frankia.
• Habitat: sandy coasts, saline sand, wind-exposed areas; very good for shelterbelts.
• Use: pulpwood, poles, fuelwood, props, and coastal protection. Grown widely on the Andhra coast as a short-rotation farm and forest crop; clones are used.
• Propagation: seed in nursery; clonal propagation by rooted cuttings.

Eucalyptus

• Family: Myrtaceae; native to Australia. Fast-growing evergreen with strong coppicing; widely planted species include E. tereticornis (Mysore gum), E. camaldulensis and E. grandis.
• Uses: pulpwood, poles, fuelwood, leaf oil (cineole).
• Propagation: seed (very fine) and clonal cuttings. Tiny seed needs shallow sowing.
• Concerns: high water use in dry areas; alleged harm to understory plants; avoid planting on wetlands and recharge zones.
• Pest/disease: gall wasps, leaf blight and seedling damping off in nurseries.

Bamboos

• Botany: grass family Poaceae, subfamily Bambusoideae; jointed hollow stems (culms) with nodes and internodes; branch systems and rhizomes underground.
• Rhizomes: pachymorph (clumping, short and thick; Bambusa, Dendrocalamus) and leptomorph (running; common in temperate bamboos).
• Common species: Dendrocalamus strictus (male bamboo, solid culms, dry deciduous forest, most widespread in India), Bambusa bambos (spiny bamboo, hollow culms, moister sites), Bambusa vulgaris, Dendrocalamus giganteus.
• Flowering: most bamboos flower after a long cycle (often decades), many gregariously over large areas, then die (monocarpic). Seed set leads to rat population build-up and food shortage in some regions.
• Propagation: seed, offset (rhizome with a culm), culm cuttings, tissue culture.
• Management: clump-based harvest of mature culms (culms older than about 2 to 3 years); keep immature culms for the clump's health.
• Uses: paper pulp, construction, mats, baskets, scaffolding, furniture. Bamboo grown on non-forest land is exempt from felling and transit permits under an amendment to the Indian Forest Act.

Other listed species (quick facts)

Regeneration and tending in practice

Natural regeneration needs seed trees, a seedbed free of thick litter, enough light and protection from fire and grazing. Artificial regeneration is by sowing seed in place (direct sowing) or planting nursery seedlings, stumps or cuttings. Planting is done in pits dug before the rains, with weeding and soil working in the first two to three years. Fire protection with fire lines and early burning, protection from browsing by fencing, and gap filling of dead plants (beating up) are standard tasks. Pruning of lower branches improves clean, knot-free timber. Poor-quality stands are improved by cutting climbers and removing defective trees. Mixed plantations reduce pest risk compared with pure stands of one species.

Exam traps

• Teak vs sandal habit: teak is a deciduous light demander; sandal is an evergreen root hemiparasite.
• Red sanders vs sandal: red sanders (Pterocarpus) has red, scentless heartwood and a dye; sandal (Santalum) has fragrant oil.
• Santalum host vs host in field: the primary (pot) host is red gram; permanent hosts are trees.
• Teak pests: defoliator eats whole leaves; skeletonizer leaves the veins.
• Casuarina nodules: Frankia (actinomycete), not Rhizobium.
• Rotation vs felling cycle: rotation is for a crop; felling cycle is the gap between fellings in the same area.
• Clear felling vs shelterwood: shelterwood removes the crop in stages under seed trees.
• Bamboo flowering: monocarpic, so clumps die after seeding.

One-liners

• 1. Teak is Tectona grandis, a deciduous tree.
• 2. Sandal is a root hemiparasite; red gram is a good host.
• 3. Spike disease of sandal is caused by a phytoplasma.
• 4. Santalol is the main constituent of sandalwood oil.
• 5. Red sanders is endemic to the Eastern Ghats of southern Andhra Pradesh.
• 6. Red sanders is listed in CITES Appendix II.
• 7. Casuarina fixes nitrogen through Frankia.
• 8. Eucalyptus is native to Australia.
• 9. Dendrocalamus strictus is the male bamboo.
• 10. Bamboo is a grass, not a tree.
• 11. Shelterwood gives even-aged regeneration under mother trees.
• 12. Teak defoliator is Hyblaea puera.

Practice questions

1. Teak (Tectona grandis) belongs to the family:

   1. Lamiaceae
   2. Casuarinaceae
   3. Santalaceae
   4. Myrtaceae
   Answer

   A. Lamiaceae

   Teak is now placed in Lamiaceae (earlier Verbenaceae).

2. Sandal (Santalum album) is best described as a:

   1. Saprophyte
   2. Stem parasite
   3. Epiphyte
   4. Root hemiparasite
   Answer

   D. Root hemiparasite

   It attaches to host roots by haustoria but photosynthesises.

3. A good primary (pot) host for sandal seedlings is:

   1. Sugarcane
   2. Cotton
   3. Red gram
   4. Paddy
   Answer

   C. Red gram

   Cajanus cajan is the usual nursery host.

4. The main constituent of sandalwood oil is:

   1. Cineole
   2. Santalol
   3. Eugenol
   4. Menthol
   Answer

   B. Santalol

   Santalol gives sandal its fragrance.

5. Spike disease of sandal is caused by a:

   1. Nematode
   2. Rhizobium
   3. Phytoplasma
   4. Fungus
   Answer

   C. Phytoplasma

   It is spread by insect vectors; infected trees are uprooted.

6. Red sanders (Pterocarpus santalinus) is endemic to:

   1. The Eastern Ghats of southern Andhra Pradesh
   2. The Himalayan foothills
   3. The Western Ghats of Kerala
   4. The Sundarbans
   Answer

   A. The Eastern Ghats of southern Andhra Pradesh

   Its natural range is a small area in the Eastern Ghats.

7. The red pigment of red sanders heartwood is:

   1. Santalol
   2. Tannin only
   3. Chlorophyll
   4. Santalin
   Answer

   D. Santalin

   Santalin is the dye principle.

8. In CITES, red sanders is listed in:

   1. Appendix 0
   2. Annexure A of CMS
   3. Appendix II
   4. Appendix IV
   Answer

   C. Appendix II

   Trade is regulated under Appendix II.

9. Casuarina fixes atmospheric nitrogen through:

   1. Frankia
   2. Azotobacter
   3. Rhizobium
   4. Anabaena
   Answer

   A. Frankia

   Frankia is an actinomycete in root nodules.

10. Eucalyptus is native to:

    1. Brazil
    2. Australia
    3. India
    4. South Africa
    Answer

    B. Australia

    The genus is Australian and was introduced in India.

11. The 'male bamboo' with solid culms is:

    1. Dendrocalamus giganteus
    2. Bambusa vulgaris
    3. Bambusa bambos
    4. Dendrocalamus strictus
    Answer

    D. Dendrocalamus strictus

    It is the most widespread bamboo of dry deciduous forests.

12. Teak defoliator is the insect:

    1. Hypsipyla robusta
    2. Cossus cossus
    3. Hyblaea puera
    4. Eutectona machaeralis
    Answer

    C. Hyblaea puera

    Hyblaea puera eats whole leaves; the skeletonizer eats between veins.

13. Most bamboos flower:

    1. Once after a long cycle and then die
    2. Never
    3. Every five years and survive
    4. Every year
    Answer

    A. Once after a long cycle and then die

    They are monocarpic and flowering is often gregarious.

14. The spiny, hollow-culmed bamboo of moister sites is:

    1. Dendrocalamus strictus
    2. Bambusa bambos
    3. Ochlandra
    4. Arundinaria
    Answer

    B. Bambusa bambos

    Bambusa bambos has thorny branches.

15. In the shelterwood system regeneration is obtained:

    1. By felling everything at once
    2. Under mother trees removed in stages
    3. By coppice shoots only
    4. By selecting single trees
    Answer

    B. Under mother trees removed in stages

    Staged fellings give an even-aged crop.

16. A common planting material for teak plantations is:

    1. Bulbs
    2. Rhizome offsets
    3. Runners
    4. Stumps
    Answer

    D. Stumps

    Seedlings are cut to a short shoot and a few cm of root.

17. Teak grows best on:

    1. Saline marsh
    2. Waterlogged clay
    3. Shallow rocky soil
    4. Deep, well-drained alluvial or loamy soil
    Answer

    D. Deep, well-drained alluvial or loamy soil

    It does not tolerate waterlogging.

18. Teak seed germination is improved by:

    1. Alternate wetting and drying
    2. Boiling for an hour
    3. Freezing
    4. Soaking in oil
    Answer

    A. Alternate wetting and drying

    This cracks the corky seed coat.

19. How does red sanders differ from true sandal?

    1. It yields sandal oil
    2. It is a conifer
    3. Heartwood is red and scentless, used for dye and furniture
    4. It is a root parasite
    Answer

    C. Heartwood is red and scentless, used for dye and furniture

    Pterocarpus is a legume with santalin pigment.

20. Sandal needs host plants because:

    1. It draws water and minerals from host roots
    2. It cannot photosynthesise at all
    3. It fixes nitrogen
    4. It has no roots
    Answer

    A. It draws water and minerals from host roots

    As a hemiparasite it is weak in root absorption.

21. The coppice system is mainly used for:

    1. Fruit production
    2. Soil salinity
    3. Very large sawlogs
    4. Fuel and poles on short rotations
    Answer

    D. Fuel and poles on short rotations

    Cheap regeneration from stump shoots.

22. The selection system gives a crop that is:

    1. Uneven-aged with all age classes
    2. Even-aged
    3. Single species only
    4. Of one height
    Answer

    A. Uneven-aged with all age classes

    Single trees or groups are harvested.

23. Low thinning removes mainly:

    1. The tallest dominants only
    2. Every tree in alternate rows only
    3. Only seed trees
    4. Suppressed and lower-crown trees
    Answer

    D. Suppressed and lower-crown trees

    It cleans the lower storey.

24. Pollarding means cutting the stem at about:

    1. Ground level
    2. 2 m height so shoots grow above browsing level
    3. Half the tree height
    4. The root collar underground
    Answer

    B. 2 m height so shoots grow above browsing level

    New shoots escape grazing.

25. A main concern about Eucalyptus planting in dry areas is its:

    1. Low coppicing ability
    2. Very slow growth
    3. High water use
    4. Nitrogen fixation
    Answer

    C. High water use

    Fast growth can draw down soil water.

26. Leaves of Leucaena leucocephala contain a toxic amino acid:

    1. Nicotine
    2. Santalol
    3. Mimosine
    4. Cineole
    Answer

    C. Mimosine

    Fodder use must be limited.

27. Pongamia pinnata is notable for:

    1. Rhizome spread
    2. Nitrogen fixation and seed oil
    3. Hemiparasitism
    4. Producing santalin
    Answer

    B. Nitrogen fixation and seed oil

    It is a leguminous tree whose seed oil is used for biofuel.

28. Bamboo clumps are harvested by removing:

    1. All culms every year
    2. Only the youngest shoots
    3. Rhizomes first
    4. Mature culms and leaving young ones
    Answer

    D. Mature culms and leaving young ones

    Mature culms are older than about two to three years.

29. Teak planted at 2 m x 2 m spacing gives how many plants per hectare?

    1. 5,000
    2. 2,500
    3. 1,250
    4. 1,111
    Answer

    B. 2,500

    10,000 / 4 = 2,500.

30. Teak planted at 3 m x 3 m gives about how many plants per hectare?

    1. 1,111
    2. 900
    3. 1,500
    4. 3,333
    Answer

    A. 1,111

    10,000 / 9 = 1,111.

31. Eucalyptus at 2.5 m x 2.5 m gives how many plants per hectare?

    1. 2,500
    2. 400
    3. 1,600
    4. 1,000
    Answer

    C. 1,600

    10,000 / 6.25 = 1,600.

32. Planting at 4 m x 2 m gives how many plants per hectare?

    1. 625
    2. 2,500
    3. 5,000
    4. 1,250
    Answer

    D. 1,250

    10,000 / 8 = 1,250.

33. 2,500 plants are needed per ha and 10% extra are provided for gap filling. How many seedlings are required?

    1. 2,750
    2. 2,600
    3. 2,510
    4. 3,000
    Answer

    A. 2,750

    2,500 x 1.10 = 2,750.

34. A teak crop has 360 m3/ha at age 30 years. The mean annual increment is:

    1. 10 m3/ha/year
    2. 12 m3/ha/year
    3. 30 m3/ha/year
    4. 15 m3/ha/year
    Answer

    B. 12 m3/ha/year

    360 / 30 = 12.

35. A stand of 1,500 trees/ha is thinned by removing every third tree. Trees removed:

    1. 750
    2. 1,000
    3. 500
    4. 300
    Answer

    C. 500

    1,500 / 3 = 500.

36. A plantation of 1,250 plants per ha has 80% survival. Surviving plants:

    1. 1,050
    2. 1,200
    3. 1,000
    4. 800
    Answer

    C. 1,000

    1,250 x 0.8 = 1,000.

37. Bamboo is planted at 5 m x 5 m. Clumps per hectare are:

    1. 400
    2. 250
    3. 500
    4. 1,000
    Answer

    A. 400

    10,000 / 25 = 400.

38. To get 4,000 usable seedlings after 20% culling, how many should be raised?

    1. 3,200
    2. 5,000
    3. 4,800
    4. 4,200
    Answer

    B. 5,000

    4,000 / 0.8 = 5,000.

39. Consider the statements: 1. Sandal is a root hemiparasite. 2. Sandal spike disease is caused by a virus. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Spike is caused by a phytoplasma.

40. Consider the statements: 1. Red sanders belongs to the genus Santalum. 2. Red sanders is endemic to the Eastern Ghats of southern Andhra Pradesh. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    It is Pterocarpus santalinus, a legume.

41. Consider the statements: 1. Casuarina fixes nitrogen with Frankia. 2. Eucalyptus is native to India. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Eucalyptus is native to Australia.

42. Consider the statements: 1. Bamboo is a grass of the family Poaceae. 2. Most bamboos flower once and then die. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

43. Consider the statements: 1. Clear felling regenerates the crop in stages under mother trees. 2. Shelterwood removes the whole crop in one cutting. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    D. Neither 1 nor 2

    Both descriptions are swapped between the two systems.

44. Consider the statements: 1. Teak is a strong light demander. 2. Teak tolerates waterlogged soil well. Which of the statements is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Teak needs well-drained soil.

45. Girdling a tree means:

    1. Cutting the stem at 2 m height
    2. Removing only side branches
    3. Digging out the roots
    4. Cutting a ring of bark and sapwood to kill it slowly and season it standing
    Answer

    D. Cutting a ring of bark and sapwood to kill it slowly and season it standing

    It is used for example to season teak before felling.