Silvicultural%20systems%20Peter%20Savill%20(University%20of%20Oxford)

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Silvicultural systemsPeter Savill(University of
Oxford)

• Department of Agriculture
• University of Reading
• 1 February 2000

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Silvicultural systems are

• The processes by which the crops that constitute
  a forest are tended, removed and replaced by new
  crops, resulting in the production of woods of a
  distinctive form.
• Name of a system is based on
• number of age classes (e.g. even-aged,
  uneven-aged), or
• regeneration method (e.g. shelterwood, selection)

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A silvicultural system involves

• method of regeneration (e.g. coppice,
  planting, natural regeneration, direct seeding)
• form of the crop produced (e.g. regular or
  irregular)
• arrangement of the crops over the forest (a form
  of normality usually aimed at)

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A sustainable 70 year-rotation in a 700 ha
even-aged forest
Area not contributing to production
Area being thinned on a cycle
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Annual planting or felling areas
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Forecast production from British forests
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Intensive versus extensive forestryFeatures Int
ensive forests

• Age distribution Even aged
• Rotation Short (45-60 years)
• Species composition Pure, exotic, clonal
• Management Cheap
• Establishment In open, by planting
• Scale of operations Large, concentrated
• Production 15-30 m3ha-1yr
• Conservation value Low

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Intensive versus extensive forestryFeatures Ext
ensive forests

• Age distribution 0 to rotation
• Rotation Long (150-200 years)
• Species composition Many, indigenous
• Management Expensive
• Establishment Under canopy, natural
  regeneration
• Scale of operations Small, scattered
• Production 3-4 m3ha-1yr
• Conservation value High

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Classification of silvicultural systems

• 1. coppice systems
• 2. high forest systems
• a) regeneration over whole forest which is
  uneven-aged polycyclic or selection systems
• b) regeneration concentrated in one part of
  forest at any one time
• i) old crop removed in several fellings over
  years shelterwood systems
• ii) old crop removed by a single felling
  monocyclic or clear felling system

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Intensive versus extensive systems

• Intensive (monocyclic) systems
• coppice
• coppice with standards
• clear felling
• (shelterwood)
• Extensive (polycyclic) systems
• selection
• group systems

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Application of coppice systems

• Where small dimensioned material is required
  (fuel wood Salix and Populus, pulp Eucalyptus)
• Generally only with broadleaved trees
• Where some forms of nature conservation are
  important
• Formerly for basket willows, farm and household
  implements, etc

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A sustainable 70 year-rotation in a 700 ha
even-aged forest
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Selection system
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Size distributions in tropical rain forest
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Number of trees per hectare at different ages in
an even-aged stand
Douglas fir, yield class 24
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Application of selection systems

• On steep sites for protection against soil
  erosion and avalanches
• Where landscape continuity is required (urban
  forests)
• Where wood production and profit are not major
  motives
• Mainly appropriate for shade bearers (beech and
  silver firs)

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Uniform shelterwood system
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Application of shelterwood systems

• Usually on rather similar sites to clear
  fellingwhere soil deterioration is not a serious
  risk
• In environments where species grown produce
  viable seed regularly (oak and beech in parts of
  Europe, sycamore and ash in UK, Dipterocarps in
  SE Asia)

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Clear felling systema typical plantation life
history for spruce (oak)

• Year
• Obtain seed -3
• Raise plants -2
• Prepare ground -0.5
• Planting 0
• Tending 4-15 (0-20)
• Thinning 20-45 (30-100)
• Clear felling 55 (120)
• Replanting second rotation

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Application of clear felling system

• On sites where forest clearance will not cause
  erosion or other problems
• Where profit is a major motive for planting
• With light-demanding species that have evolved in
  monocultures (often pines, spruces, eucalypts)

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Group system
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Choice of system depends on

• Regeneration ecology of trees
• Site, topography, soil
• Wildlife
• Pests and diseases
• Fire
• Climatic risks
• Size, age, vigour of existing stand
• Introduction of new genotypes
• Financial constraints

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Patterns of volume increment for an even-aged
stand
Yield Class
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Mean annual increment curves for different species
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Mean annual increment curves for a single species