Silvicultural systemsPeter Savill

(University of Oxford)

Department of Agriculture

University of Reading

1 February 2000

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)

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)

A sustainable 70 year-rotation in a 700 ha

even-aged forest

Area notcontributingto production

Area being thinnedon a cycle 70 year

old, clearfelled

Annual planting or felling areas

Forecast production from British forests

Intensive versus extensive forestry

Features Intensive 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

Intensive versus extensive forestry

Features Extensiveforests

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

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

Intensive versus extensive systems

Intensive (monocyclic) systems

coppicecoppice with standardsclear felling(shelterwood)Extensive (polycyclic)

systemsselectiongroup systems

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

A sustainable 70 year-rotation in a 700 ha

even-aged forest

Selectionsystem

Size distributions in tropical rain forest

Number of trees per hectare at different ages in an even-aged stand

Douglas fir, yield class 24

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)

Uniform shelterwood system

Application of shelterwood systems

• Usually on rather similar sites to clear felling—where 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)

Clear felling system:a 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

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)

Group system

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

Patterns of volume increment for an even-

aged stand

maximumM.A.I.

= Yield Class

Mean annual increment curves for

different species

Mean annual increment curves for a

single species