Silvicultural Practices in Agroforestry

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Role of Silviculture in Forest Management
Syed Zahid Hasan
Dept. of Agroforestry and Environmental Science I Sylhet Agricultural University

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Role of Silviculture in Forest Management
Silvicultural practice consists of the interventions applied to forests to maintain or enhance their utility
for specific purposes, such as the production of wood and other forest products, biodiversity
conservation, recreation and the provision of environmental services.
Silviculture
The art and science of reproducing and growing trees and forests in a sustainable manner based on
principles of forest ecology for the benefit of society.
The aim of silviculture
Silviculture is a set of techniques that can be applied to help attain specified forest management
objectives. It aims to achieve the implementation of objectives through manipulation of the composition
and structure of a forest. In most instances in a wood production forest, the aim of silviculture is to
enhance the growth and quality of potential crop trees.
Silvicultural systems
A silvicultural system is a series of forestry practices using natural strategies designed to regenerate
specific forest types according to landowner objectives.
• Clearcutting
• Shelterwood
• Selection
• Intermediate Treatments
• Artificial Regeneration
Natural regeneration
Most of our forests are regenerated using natural strategies in silvicultural systems.
Planting is not necessary but can be successful.
Clearcutting
An even-aged system where all or nearly all of
the trees are harvested at one time.

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Shelterwood
An even-aged system where one or two cuts are used prior to the final harvest. The first two cuts
stimulate and establish advanced regeneration before the final harvest cut.
Final Crop Should Be:
• Windfirm
• Good Seeders
• Undamaged by Logging
Selection
An uneven-aged system where trees of all sizes are harvested on a cycle of about 10-15 years.
A selection harvest IS NOT a diameter-limit cut!
Intermediate treatments
Nearly any forestry practice not connected with regeneration or harvest can be considered an
intermediate treatment.
• Timber Stand Improvement (TSI)
• Weeding, Cleaning, Sanitation Cutting
• Protection
• Pruning

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Timber stand improvement
TSI thinning are intended to improve the quality of a timber stand. They can be commercial or non-
commercial.
Artificial regeneration
We usually think only of the physical act of planting trees, but there is much more to consider in order
to achieve success.
• Species Selection
• Planting Methods
• Site Selection
• Competition Control
• Direct Seeding
• Site Preparation
• Underplanting
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 (monocyclic) systems
• Coppice
• Coppice with standards
• Clear felling (shelterwood)
Extensive (polycyclic) systems
• Selection
• Group systems

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Group System

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Silvicultural Systems
Silvicultural systems in natural forests can be categorized broadly as either monocyclic (“uniform”,
“even-aged”) or polycyclic (“selective”, “uneven-aged”).
a. Polycyclic System is applied in all-aged forests where the log harvest is cut from specified size-
classes and species of trees at intervals which are about one-half of the growing period taken to reach
industrial log sizes. Advanced growth is retained. There is one sub-system.
b. Selection Cutting of Crop Trees: Aims at maintaining uneven aged forests; regeneration is either
present before logging or can be encouraged to develop following harvesting by leaving seed, or
mother, trees; a range of tree size classes exists and the forest does not have a uniform composition.
c. Monocyclic Systems are applied in uniform forests where age-classes exist or are to be formed.
New crop trees are derived from regeneration, seedlings and. saplings of commercially important
species and not from older and larger trees which may have or still do comprise the forest structure.
Advanced growth is retained. At the end of a fixed rotation crop trees are either removed by
clearcutting or, in the case of the uniform shelterwood system, harvested through a regeneration
period. There are three sub-systems.
d. Uniform System: Aims at achieving even-aged stands composed of trees of generally uniform size:
regeneration is present in sufficient density before harvesting to provide tree stocks for the next crop.
e. Tropical Shelterwood System: Aims at achieving even-aged stands through the formation of a
shelterwood of mother (seed) trees which are subsequently removed when regeneration has become
established.
f. Irregular Shelterwood System: Aims at achieving continuing forest development in situations
where regeneration is uncertain and retention of trees below specified cutting limits is necessary and
will comprise a part of a future crop.
The relationship of silviculture to forest management objectives

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The following guidelines should be considered in designing an appropriate silvicultural system for a
forest management unit:
• The forest planner should provide an appropriate basic framework for silvicultural treatment.
The framework should include clear management objectives.
• The silvicultural concept should express basic principles but should leave firm decisions on the
nature of specific silvicultural operations - what and when specific activities will take place - to
local foresters.
• The definition of short- and medium-term stocking and regeneration targets is an important step
in achieving a desirable forest composition and structure. Diagnostic sampling should be applied
as a step in determining stocking and regeneration targets.
Barrier and cover approaches
Barrier approaches: The barrier approach to erosion control is to check run-off and soil removal by
means of barriers. These may be earth structures (ditch-and-bank structures, terraces), grass strips or
hedgerows. Agroforestry can contribute to the barrier approach directly, through the use of hedgerows
as partly permeable barriers, and indirectly, through the role of trees in stabilizing earth structures and
making productive use of the land they occupy.
Cover approaches: The cover approach to erosion control is to check raindrop impact and runoff through
maintenance of a soil cover formed of living and dead plant materials, including plants, crop residues
and tree litter and pruning. Agroforestry can contribute to the cover approach through use of tree litter
and pruning, in combination with the living crop residues.

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Decisions on silviculture in forest management can occur at three levels:
(i) Silvicultural systems; (ii) Silvicultural treatment regimens; and (iii) Silvicultural operations
i. A silvicultural system is “the process by which the crops constituting a forest are tended, removed
and replaced by new crops, resulting in the production of stands of distinctive form ... The terms
‘stand’ and ‘crop’ are both used to denote silvicultural or management units that are homogeneous
in one or several aspects” (Matthews 1994).
ii. A silvicultural treatment is a planned programme of silvicultural operations that can be
implemented during the entire or partial rotation of a stand. Within the context of silvicultural stand
treatment, each stand is assigned a specific silvicultural objective and separately assessed for the
characteristics of its site (e.g., locality, slope and soil type) and stocking (e.g. composition, age,
diameter distribution and regeneration). Based on this information, a silvicultural treatment
regime is formulated.
iii. Silvicultural operations are procedures that aim to achieve stand-specific objectives by using
silvicultural techniques. Such techniques include, for example, canopy alterations to induce natural
regeneration, the harvesting of mature trees, planting, and thinning to improve timber quality and
stand growth. Silvicultural operations involve decisions on machinery and other equipment,
techniques, work organization and human resources, as well as considerations of operational cost
and investment.
Conclusion
In planning silvicultural interventions, forest managers should ensure they have adequate biological and
socioeconomic information on the forest (see Forest Inventory), as well as sufficient knowledge of
operational aspects such as weather, access, funding and human resources. Forest managers should also
have a good understanding of the ecology of the forests in which interventions are planned, especially
the structure of the existing stand and the requirements for ensuring the adequate regeneration of
desirable species.