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Silvicultural systems Peter Savill (University of Oxford)

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1 Silvicultural systems Peter Savill (University of Oxford)
Department of Agriculture University of Reading 1 February 2000

2 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)

3 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)

4 A sustainable 70 year-rotation in a 700 ha even-aged forest
Area not contributing to production Area being thinned on a cycle 70 year old, clear felled

5 Annual planting or felling areas

6 Forecast production from British forests

7 Intensive versus extensive forestry Features Intensive forests
Age distribution Even aged Rotation Short ( years) Species composition Pure, exotic, clonal Management Cheap Establishment In open, by planting Scale of operations Large, concentrated Production m3ha-1yr Conservation value Low

8 Intensive versus extensive forestry Features Extensive forests
Age distribution 0 to rotation Rotation Long ( years) Species composition Many, indigenous Management Expensive Establishment Under canopy, natural regeneration Scale of operations Small, scattered Production m3ha-1yr Conservation value High

9 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

10 Intensive versus extensive systems
Intensive (monocyclic) systems coppice coppice with standards clear felling (shelterwood) Extensive (polycyclic) systems selection group systems

11 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

12 A sustainable 70 year-rotation in a 700 ha even-aged forest

13 Selection system

14 Size distributions in tropical rain forest

15 Number of trees per hectare at different ages in an even-aged stand
Douglas fir, yield class 24

16 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)

17 Uniform shelterwood system

18 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)

19 Clear felling system: a typical plantation life history for spruce (oak)
Year Obtain seed -3 Raise plants -2 Prepare ground -0.5 Planting Tending (0-20) Thinning (30-100) Clear felling (120) Replanting second rotation

20 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)

21 Group system

22 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


24 Patterns of volume increment for an even-aged stand
maximum M.A.I. = Yield Class

25 Mean annual increment curves for different species

26 Mean annual increment curves for a single species

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