1. Silviculture Elements of Forestry Kenneth Williams
Fisheries Extension Specialist
Langston University Aquaculture Extension Program

2. Silviculture
- “Growing trees”. The biological aspect of forest management subject to economic and environmental constraints.
Purpose – to enhance timber production, wildlife habitat, stream flow and the aesthetic qualities of the forest.
The manipulation of forest stands to accomplish set objectives.

3. Silviculture
Much effort has been devoted to increasing growth rates of forest stands.
Silviculture practices can be used to benefit non timber values. Ex. Prescribed burning to improve wildlife habitat.

4. Silviculture
Silviculture practices may be designed to mimic natural processes in forest development but often in ways that speed natural development.

5. Even-aged stand development
Begins with sudden removal of the tree canopy by logging or by natural means such as fire or wind storms.

6. Even-aged stand development
Seedlings quickly establish themselves on the open, sun lit ground.
Even-aged stand development

7. Even-aged stand development
In years the seedlings have grown enough to form a new closed canopy of trees all about the same age. This is a young forest and is called an even-aged stand.
Even-aged stand development

8. Even-aged stand development
Existence of an even-aged stand indicates that that the previous stand was removed over a short period of time. Whatever the cause.
Seedling establishment can take over 10 years, so even-aged stand trees can be years old in a young stand.

9. Even-aged stand development
Trees are all about the same size in a young stand but as the stand matures, tree size varies due to species and individual tree genetics.
Even-aged stand development

10. Classification of even-aged stands by size
Seedlings – less than 1 meter tall (3.3 ft.)
Saplings – taller than 1 m. up to 4 inches in diameter.
Poles – trees 4-10 inches in diameter.
Mature – inches in diameter.
Overmature – A large number of the trees becoming senescent.

11. Seedling

12. Sapling

13. Pole

14. Mature

15. Even-aged stands
Rotation age – The age of the stand at the time of a planned harvest.

16. Competition in even-aged stands
Competition for light and other resources is severe in young stands.
The canopy of slower growing trees may be covered by other trees and not receive adequate light.
Trees are often categorized by their position in the canopy.

17. Dominant – Trees that project somewhat above the general level of the canopy. They receive direct sunlight from above and some from the side.
Crown classes

18. Crown classes
Codominant – Canopy trees of average size that receive direct sunlight from above but little light from the sides.

19. Crown classes
Intermediate – Trees with crowns extending into the canopy layer but crowded on all sides. Only the top of the crown receives direct sunlight.

20. Crown classes
Suppressed – Trees with crowns completely overtopped by surrounding trees. They receive no direct sunlight except for where small gaps in the canopy exist.
Once a tree has become suppressed it has little chance of regaining a dominant position in the canopy.

21. Crown classes
Dominant Codominant Intermediate Suppressed

22. Even-aged stand maturation
Suppressed trees have a high mortality rate.
Tree numbers in even-aged stands are reduced by 50-60% by competition in about 40 years. This is a self-thinning process.

23. Even-aged stand maturation
Small trees growing beneath the canopy may not be younger than much larger trees.
In fast growing stands, intermediate trees may become suppressed in the near future.

24. Uneven-aged stands
Even-aged stands gradually become uneven-aged stands in which 3 or more age classes are intermixed.
By the time the stand reaches the pole stage an understory of shrubs and seedlings has developed.
When mature canopy trees begin to die at different ages, gaps in the canopy are filled with understory trees.

25. Even-aged stand maturation
In uneven-aged stands, suppressed trees are often younger than overstory trees.
Uneven-aged stands are characteristic of the later successional stages.
Because replacement trees often grow in the shade and in small gaps in the canopy, these stands are often dominated by shade tolerant species.

26. Pure versus mixed stands
Under natural conditions trees may occur in nearly pure stands of a single species or in mixtures.
Pure stands are often even-aged and result from some catastrophe.
When pure stands are established artificially they are called monocultures.
Pure versus mixed stands

27. Pros of pure stands Easier to manage pure stands.
Lower costs of cultural treatments and harvest methods.
Economic value often greater than a mixed stand.

28. Pros of mixed stands More aesthetically pleasing.
Greater carrying capacity for wildlife.
More insect and disease resistant, but not always.

29. Treatments to improve existing stands
Spacing and stand density adjustment.
Removal of poorly formed or diseased trees.
Pruning
Salvaging dead or dying trees
Fertilization

30. Treatments to improve species composition
Sometimes difficult – some species may be very well adapted to the site and difficult to suppress.
Best done when favored trees are very young and still capable of responding to release from competition.

31. Treatments to improve species composition
Release cuttings are performed to free desirable seedlings and saplings from trees of competing species that have already or probably will soon suppress crop trees.
Release cuttings are often required in young conifer stands if intermixed with aggressive hardwoods.

32. Treatments to improve species composition
Improvement cuts – in pole and mature stands remove diseased or poorly formed trees and trees of undesirable species.
Economics dictate removal only of undesirable trees that clearly interfere with a promising crop tree.
If crop tree already dominant, further tree removal would have no effect on growth.

33. Treatments to increase growth rates
Stand density and tree growth are regulated primarily by thinning.
Thinning does not effect total wood production per acre, however, remaining trees become larger and more valuable.
Thinning results in a more open stand of larger trees and accelerates the natural outcome of competition.

34. Tree thinning methods
Low thinning – a light, low thinning would only remove suppressed and intermediate trees.
A heavy, low thinning also removes some codominant trees. This releases dominant tree growth and is a preferred method.

35. Low thinning
Before
After

36. Tree thinning methods
High thinning – the objective is to create sufficient numbers of small gaps in the canopy to stimulate growth of better crop trees.
Removal of intermediate and codominant trees of smaller size or poor quality.
Suppressed trees usually not removed.

37. High thinning
Before
After

38. Mechanical thinning Trees removed in strips regardless of crown class.
Quick and inexpensive.
Trees next to cut areas benefit.
Works well in plantations. Where every 3rd row of trees are cut.

39. Thinning Intensively managed stands are thinned about every 10 years.
Thinning is sometimes delayed until thinned trees can be used as pulpwood or firewood.
Young, even-aged stands are thinned to improve wildlife habitat and recreation.

40. Thinning
Light thinning speeds development of a forest of large stately trees.

41. Fertilization
Fertilization is only used in areas where known deficiencies exist. Here they can increase growth %.
Fertilization is expensive and can cause pollution problems.
Some forest types show no response to fertilization.

42. Forest stand regeneration
In any partial timber harvest it is important to remove some low-quality trees along with good trees. This combines a harvest cut with an improvement cut.
It is very important to leave a few very good trees.

43. High grading
High grading- The removal of all good trees from a stand. This results in lowering the genetic quality of the stand over time, resulting in long term damage to stand quality and economic value.
High grading degrades forests.

44. Natural regeneration
Seedlings and saplings already present under the forest stand to be cut. Also called advanced regeneration.
Many hardwoods sprout from cut stumps. This is an important form of regeneration in hardwood forests.
Natural regeneration is more successful in humid areas than in semiarid climates.

45. Advanced regeneration

46. Natural regeneration not always successful
Adequate seed production in some species may occur almost every year but in others only at long intervals.
Ex. Red pine – seed crops every 7 years.

47. Natural regeneration not always successful
Seedling germination and survival in some species is greatly influenced by weather.
The microclimate of the stand must be favorable for regeneration.
Ground surface or seedbed must be in good condition. Scarification or burning may be necessary to remove duff.

48. Natural regeneration not always successful
Dense advance generation and shrub and sprout layers may prevent establishment of desirable species.
Seed and seedling predators are sometimes responsible for regeneration failures.
Ex. Insects, mice and deer.

49. Artificial regeneration
Artificial regeneration is accomplished either by directly planting seeds or seedlings on a harvested site.

50. Artificial regeneration
Artificial regeneration is used in intensively managed forests that are harvested at short intervals.

51. Advantages of artificial regeneration
Stand establishment more reliable.
Increases chances of prompt reforestation.
Timing can coincide with favorable weather conditions.
Greater control over species composition.
Greater control over tree spacing and subsequent growth.
Seeds and seedlings can be derived from genetically superior stock.

52. Direct seeding
Can be done from the ground by hand or machine or from the air.
Cheaper than planting.
Less control over spacing.
Lower success rate.
Very useful for covering extensive areas by air after a major fire or on steep or irregular terrain.

53. Planting High success rate with seedlings.
Containerized better than bare root but more costly.
Site preparation important. Mechanized equipment usually used for this, however, steep slopes and environmentally sensitive sites may be burned.

54. Seedling losses Mice, other rodents and deer.
Competition from shrubs and sprouting stumps.

55. Planting
Planting is a large portion of total cash investment in a forest stand.
Planting is only done when the increased cost can be justified.

56. Silvaculture systems
Silviculture systems are classified by method of harvest and regeneration and generally grouped under even-aged and uneven-aged methods.

57. Even-aged methods
Clearcutting – regeneration by natural seeding, direct seeding or planting.
With natural seeding, effective dispersal distance of seeds may limit the width of the clearcut.

58. Even-aged methods-problems with natural regeneration
Clearcutting a shade intolerant forest that has a dense understory of more shade tolerant species will change forest composition.
Ex/ Southern pines with a hardwood understory.

59. Clearcutting method Artificial regeneration preferred.
No biological restriction on cutting width.

60. Seed tree method
Scattered mature trees are left on the site to serve as a seed source and to provide uniform seed dispersal.
Works best with intensive site preparation and deeply rooted trees.
This method does not always produce enough seedlings.

61. Seed tree method

62. Shelterwood method
Seed trees left in sufficient numbers to provide shade and shelter to seedlings.
30-80% of crown story removed.
After several years, the rest of the crown story is harvested.
This method is used for species that do not germinate well under open conditions.

63. Shelterwood
This method produces the least erosion and looks the best of even-aged methods.
Trees retained are among the larger and better quality trees In the stand so they will be a good seed source.

64. Shelterwood Forest cut About 40% of mature trees left
After a new stand is established the rest of mature trees are cut

65. Coppice method Depends on regeneration by stump sprouts.
Restricted to species that sprout vigorously and sprouts can obtain a commercial size.
Ex. Aspen and oak.
Usually managed on short rotations for pulp and firewood.

66. Provision for sustained yield
In all forms of even aged management, yield is sustained by cutting parts of the total property at regular intervals so that when the cutting cycle is complete, trees from the 1st tract will be ready to cut again.

67. Uneven-aged methods
Advantages – No need for site preparation. natural regeneration is reliable and the only method where sustained yield can be obtained from a single stand of trees.
Forest canopy stays largely intact.
Fire hazard is minimal because no piles of logging debris.
Used by small land owners and managers of multiple-use recreation areas.

68. Uneven-aged methods
Disadvantages – Generally only shade tolerant species work well.
Most appropriate for tolerant species
Ex. Maple, hemlock, cedar, spruce and fir.
Unfavorable to some wildlife species. Group selection helps.
Difficult to prevent injury to nearby trees.
Can resemble high grading if only best trees cut.

69. Choice of management methods
Depends on goals and constraints
Uneven-aged methods best for sites where tolerant species are valuable and in demand.
Does not work well for many commercially valuable shade intolerant species.
Costs of each method must be evaluated.

71. Soil erosion
Leaf litter and ground vegetation usually prevent erosion on most sites except for steep slopes and unstable soils.
Road construction and skidding operations cause erosion.

72. Nutrient loss
Natural replenishment of nutrients work well on long rotation cuttings.
Short rotations 40 years or less, increase nutrient loss.
Whole tree harvesting increases nutrient loss. Most nutrients in branches and leaves not trunk.

73. Chemical Use Fertilizer Herbicide
Little use of either in most situations.

74. Natural precedent for harvest methods
Uneven-aged systems - natural death of mature trees.
Even-aged management – Fire, wind storm or insect damage.

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