Silviculture - PowerPoint PPT Presentation

1 / 75
About This Presentation
Title:

Silviculture

Description:

Langston University Aquaculture Extension Program Silviculture - Growing trees . ... tree size varies due to species and individual tree genetics. – PowerPoint PPT presentation

Number of Views:225
Avg rating:3.0/5.0
Slides: 76
Provided by: luresextE
Category:

less

Transcript and Presenter's Notes

Title: Silviculture


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.

7
Even-aged stand development
  • In 10-20 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.

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 20-30 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.

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 10-24 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
Crown classes
  • Dominant Trees that project somewhat above the
    general level of the canopy. They receive direct
    sunlight from above and some from the side.

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.

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
    20-100.
  • 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.

70
(No Transcript)
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.

75
THE END
Write a Comment
User Comments (0)
About PowerShow.com