Silviculture

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Silviculture

• Definition
• Objectives
• Terminology
• Regeneration methods

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Silviculture

• Definition
• The management of forest vegetation to meet
  objectives
• Includes the theory and practice of controlling
  forest establishment, composition, structure and
  growth

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Silvicultural objectives

• To increase wood production
• To enhance wildlife habitat
• To enhance scenic values
• To enhance recreational opportunities
• To enhance grazing for domestic livestock

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Silvicultural objectives

• To enhance water quality and quantity
• To enhance forest health
• To diminish susceptibility to stand-replacing
  wildfires
• To enhance ecosystem functioning

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Silvicultural objectives

• May be complementary to one another
• May vary by the type of ownership and objectives
  of the owners

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Silvicultural Practicescommonly classified as

• Harvest /regeneration methods
• Intermediate treatments

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Harvest /regeneration

• Harvest/regeneration may rely on natural
  seedfall, vegetative propagation, direct seeding
  or planting to obtain adequate stocking
• NFMA specifies that sites must be regenerated
  within 5 years of harvest
• Idaho State Forest Practices Act also specifies
  that site must be adequately regenerated within 5
  years

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Natural regeneration
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Regeneration by planting
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Planted forest
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Silvicultural practices can result in different
age structures

• Even-aged
• Stand may be considered even-aged if all of the
  trees are within 20 age range at rotation
• Un-even-aged
• Three or more age classes is considered an
  un-even-aged forest or multi-aged forest

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Silvicultural practices can result in different
age structures

• All-aged forest
• Hardly ever happens in nature
• May get waves of regeneration due to variation in
  weather, seed crops, soil moisture during
  germination period and first growing season, and
  variation in predator populations

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Lodgepole pine - even-aged, dog-hair stand
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Uneven-aged stand - mixed species
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Silvicultural Practices

• Harvest /regeneration methods that result in
  even-aged stands
• Clearcut method
• Seed-tree method
• Shelterwood method
• Coppice method
• Variations on the themes

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Original Fully-Stocked Stand
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Clearcutting method

• All trees in the treatment area are removed

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Clearcutting method

• New stand may include seedlings from advanced
  regeneration, natural seedfall, direct seeding or
  planting

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Clearcut viewed from above
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Seed Tree Method
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Seed tree harvest/regeneration

• Harvest removes most of the mature trees from the
  original stand
• Best 1 to 10 trees per acre left on site

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Seed tree harvest/regeneration

• Seed trees serve as seed source for next stand
• Provides more uniform disperal of seed
• Well-suited to wind-firm, intolerant species

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Seed tree harvest/regeneration(near Libby,
Montana)
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Original Fully-Stocked StandShelterwood Method
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Shelterwood method

• Preparatory cut removes 25-30 percent of the
  trees
• Promotes wind-firmness in remaining trees
• This step is often skipped

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Shelterwood method Seed tree step

• Seed tree cut removes all but the best trees
  about 20-30 mature trees/acre left on site
• Opens canopy to allow new seedlings to get
  established

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Shelterwood methodOverstory removal

• Overstory removal harvests remaining mature trees
• This step is done after new seedlings are
  well-established

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Shelterwood harvest/regeneration(north of
Potlatch, Idaho)
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Silvicultural Practices

• Harvest /regeneration methods that result in
  uneven-aged stands
• Single-tree selection method
• Group selection method

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Individual Tree SelectionA small number of trees
are removed on a regular cycle
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Group SelectionSmall groups of trees removed in
repeated entries
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Retention HarvestingRetains 15-20 percent of
preharvest stand
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Retention harvest
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Silvicultural practicescan affect

• Types of species that regenerate
• Even-aged methods favor intolerant species
• Uneven-aged methods favor tolerant species

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Silvicultural practicescan affect

• Forest structure
• Vertical and horizontal arrangement of vegetation
  within the stand
• Vegetation may all be at same level or at
  multiple levels within the forest canopy

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Silvicultural practicescan affect

• Composition (species mix)
• Usually expressed in percent ()
• Pure stand 100 single species
• Mixed species stands usually described by percent
  of each species

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Silvicultural Practices can affect

• Stand density
• Can be expressed as the number of trees per acre
  (TPA)
• Stand may have 2,000 to 3,000 TPA at year 1 and
  only 300 TPA at maturity

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Silvicultural Practices have an effect on

• Stand density
• Can also be expressed as basal area/acre
• Basal area equals the cross-sectional area of
  trees expressed in square feet at breast height
  (4.5 ft.)
• Example 180-200 square feet basal area is
  common in northern Idaho
• Management guidelines can describe the target
  basal area/acre at a certain age
• Neither TPA nor BA is adequate by itself to
  describe stand density

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Crown class distribution

• Refers to the position of the live crowns in the
  forest canopy
• Crowns classified as
• dominant crown extends above the main canopy
• co-dominant crown helps form the general level
  of the main canopy
• intermediate crown is in lower portion of main
  canopy
• suppressed crown is completely overtopped by
  neighbors

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Rotation vs Cutting Cycle

• Rotation
• Applies to even-aged stands
• Refers to the time between regeneration and
  maturity (time of harvest)
• In southeast US - 35 years In Idaho - 120 years
• Cutting cycle
• Applies to uneven-aged management
• Refers to the time interval between harvest
  entries

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Regeneration

• Success will depend on
• The way the original stand was harvested
• Follow-up treatments
• Availability of seeds or other propagules
• Biological and ecological appropriateness of the
  regeneration materials to the site
• Speed with which regeneration materials reach the
  site
• Weather conditions during regeneration

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Silviculture

• Approaches to management
• Commodity /financial efficiency
• managing forests to provide timber products in
  the most financially efficient manner
• Preservation
• management by reserving forests so that no
  commodity products are extracted
• Integration
• managing forests to provide a variety of
  commodity and non-commodity values, including
  timber, wildlife habitat and recreational
  opportunities

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Silvicultural Prescription

• Plan that translates land management objectives
  into silviculturally sound treatments

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Silvicultural Prescriptions

• To prepare a silvicultural prescription
• Determine the current condition
• Define the desired condition
• Develop a plan on how to achieve the desired
  condition, given the current condition

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Silvicultural Prescriptions

• Prescription should address the implications of
  proposed actions for related resources and
  resource use
• Prescription should address the implications of a
  do nothing alternative