Combination of Silvicultural Systems

COMBINATION OF SILVICULTURAL SYSTEMS

1.   A combination of systems means the adoption over the same area of two or more different forms of felling and regeneration in close relation with each other.
2.   It does not mean the application of different systems on separate self-contained areas under the same general pattern of management if each of these systems is worked independently of each other. e.g.
·       A tract of hilly country;
·       The higher ridge may be worked under the selection system (for reason of protection);
·       The main part of the area under some regular High Forest System and the outer edges with coppice with STANDARDS SYSTEM to meet the local demands of fuelwood, small timber etc.
·       Under a combination of system, the various forms of felling may be applied:-
i.       Either together; as when UNIFORM AND GROUP fellings are carried out simultaneously
                  or
ii.   Consecutively for when regeneration is started by means of uniform fellings and ended with the help of subsequent strip fellings passing over the same area occur.
3.   The term concentrated fellings is a very convenient one to adopt in the case of a COMBINATION of fellings of different types, aimed to regenerate definite areas within a fixed period of time.


CHOICE OF SYSTEMS

1.   Before the choice of a silvicultural system, the following factors should be taken into account and careful study of the prevailing conditions in any given locality:-
      FACTORS:           (a)       Silvicultural and protective factors
                                    (b)       Economic Factors

(a) Silvicultural and protective factors

i.    Regeneration conditions
ii.   Growth conditions
iii. Nature of Terrain and soil
iv.  Protection against External dangers

(b) Economic Factors

i.    Personal and labor
ii.   Type of produce needed
iii. Economic considerations
iv.  Factor of transport

REGENERATION CONDITIONS

1.   The application of the coppice system is limited only to those species which are good coppicers.
2.   Where the seeding is sporadic or irregular in nature, the selection or the irregular shelterwood systems would give a fair result.
3.   If the effect of the sun is adverse on the Natural Regeneration, some shelterwood system over a long period may be adapted.
4.   While the forests have been rendered unproductive through faulty treatment measures and comprise of a few seed bearers, along with many weed infested blanks, the system is applied under these conditions is the CLEARFELLING with Artificial Regeneration.


GROWTH CONDITIONS

1.   The selection and irregular shelterwood system favor shade bearers as compared to light demanding species.
2.   In the Two Storied High Forest System, the species having a slower growth rate may be shade bearer.
3.   Strong light demanders are best suited to be worked under the clearfelling system; the clear strip system or any short shelterwood system with very open seeding fellings.

NATURE OF THE TERRAIN AND SOIL

1.   The nature of terrain and soil influence the choice of system to a great extent:-
2.   Adaptation of CLEARFELLING SYSTEM should be avoided in areas which are subject to severe soil Erosion, Landslides, Avalanches, in water catchment Areas and the place where the soil is likely to deteriorate rapidly when exposed.
3.   The Irregular shelterwood system; Two storied High Forests System and the selection system can be applied in areas which are liable to severe soil erosion. e.g.
      A large number of the coniferous forests are being worked under the Punjab irregular shelterwood system, with minor modifications.
4.   On rocky hillsides and precipitous slopes, where regeneration occurs in only a few pockets, the selection system is best suited.

PROTECTION AGAINST EXTERNAL DANGERS

1.   The uniform system has been considered to be best suited for areas which are subject to the furry of wind storms.
2.   In areas where snow damage occurs, an uneven-aged system like THE SELECTION or the irregular shelterwood system is adopted.
3.   Safeguard against damage by frost and sensitive species under protective cover the shelterwood system, or the strip felling system or the two storied high forest system is adopted. Fillings proceed from North to South.
4.   Where the incidence of grazing and browsing in high, it is not possible to adopt any of the coppice systems.
5.   In localities which are prone to frost, the CLEARFELLING or coppice system should not be adopted.
6.   In areas which are prone to insect attack clearfelling system is not advisable but an irregular system may be adopted.
7.   Standers may have to be left if there is a Risk of Fire occurrence.

PERSONNEL AND LABOUR

1.   The clearfelling and the coppice systems are the best suited where there is no need for a very high degree of skill.
2.   The selection system is the most difficult to operate as it requires technical skill.
3.   As per as labor required per unit outturn, the clearfelling system the Least Labour for and coppice with standards system need the highest.


TYPES OF PRODUCE NEEDED

1.   Where there is demand for small size timber for fuelwood purposes etc the coppice system is best suited.
2.   When there is a demand for large size timber any high forest system may be adopted.
3.   For meeting a mixed local demand for fuelwood together with poles and large size quantity the coppice with standards system is suited.
4.   The High Forest System is able to meet a demand for clean, cylindrical timber of a good quality.
5.   The produce obtained under the SELECTIN system is more tapering and branch.
6.   The two storied high forest with standards system is best suited for the production of clean, straight and large sized timber.
7.   Where conifers are raised primarily for the production of mining Timber and pulpwood, the CLEARFELLING system is the best suited.

ECONOMIC CONSIDERATIONS

1.   Keeping the cost of felling, conversion, and extraction in view the CLEARFELLING system and the coppice systems are the best and the SELECTION system, least suited.
2.   Among the High Forest Systems, those with a short regeneration period are more beneficial than those with longer periods.
3.   Early returns are available in case of the coppice systems.
4.   Among all the High Forest Systems, the Two storied high forest provides the earliest returns in the form of yield from the thinning of the underwood.
5.   The highest financial returns may be obtained by adopting the CLEARFELLING system with Artificial Regeneration. A short rotation is adopted is such cases.
6.   The even-aged systems furnish early returns than compared to the uneven-aged ones.

FACTORS OF TRANSPORT

1.   The selection system is best suited for areas where there is a lack of roads for extraction.
2.   If there is a well-developed network of roads, the CLEARFELLING, strip and coppice systems can be applied successfully.

AESTHETIC FACTORS

1.   Those systems which maintain more or less continuous green cover.

RIGHTS AND CONCESSIONS

In case of grazing rights, it is advisable to adopt a short period system than long period ones.

CHANGE OF SYSTEMS

·       The following factors may necessitate changing from one silvicultural system to another:-
1.   Change in the market demand.
2.   For reason of policy e.g. policy favoring conservation then selection system may replace the clearfelling system.
3.   Improvement in personnel, both in terms of number and technical skill.
4.   Man’s knowledge of silviculture increases, thus a change in the silvicultural system may be needed.
5.   Improved communication e.g. with the improvement of road and interior forest of a good coppicing species may be shifted from the selection system to the coppice system.
6.   Sometime a silvicultural system may have been wrongly selected, later on, the amendment is made by change the system.


THE DEVELOPMENT AND CHARACTERS

                                    OR

HIGH FOREST SYSTEM

Ø  The following is a brief history of the main systems:-
1.   The CLEARFELLING system perhaps has the oldest history. Since times immemorial, man has been clearfelling forests for expansion of human habitation, silvicultural and economic reasons.
2.   The SELECTION system in its present form is believed to have been originated from a primitive idea. It has been followed for felling forests since the early times.
3.   The UNIFORM system has been developed over the last three or four centuries. It was first applied in its present form by Martin, in the middle of the last century. It is believed that this system was evolved from the now outdated tire et air system of France.
4.   The GROUP system was first presented on the scientific basis by GAYER in the second half of the last century, although it was used in a somewhat crude form, earlier also.
5.   The SHELTERWOOD system is a development of the uniform system.
6.   The STRIP system has been suitably modified to give the WEDGE system and WAGNER’S BLENDERS AUMSCHLAG.
7.   Most of today’s systems owe their origin to EUROPE, though minor variations have crept in, here and there in the countries where they are practiced.

PRESENT DAY CONCEPTS

Ø  The modern day concepts in silvicultural systems are:-
(a) Regeneration
(b) Ecology
(c) Intensive and Extensive Application
(d) Regularity and Irregularity

(a) Regeneration

i.    Today, a large number of foresters favor the establishment of regeneration by natural means, rather than artificial methods.
ii.   The technical knowledge of a forest officer is judged by his skill in obtaining Natural Regeneration.

(b) Ecology

i.    Ecology has become an important factor in the silvicultural treatment of forests.
ii.   Ecologically speaking, regeneration fellings are nothing but a process in which the occurrence and subsequent establishment of regeneration are stimulated.
iii. It becomes imperative to study the conditions which can be affected by the partial or complete removal of the canopy such as:
1.   Decreasing or increasing of root competition;
2.   Increasing incoming solar radiation to the forest floor.
3.   Alteration of soil condition.
4.   Change in the level of natural soil erosion.

(c) INTENSIVE AND EXTENSIVE APPLICATION

i.    Under contain conditions, intensive treatment over a small area may be substituted for extensive treatment over a larger area.
ii.   In the under-developed countries too, the forest area cannot be appreciably increased. In these circumstances, there is no option but to go in for intensive silvicultural treatment, so as to maximize production from forests.
iii. Intensive treatment of forests should be brought only after a detailed study regarding soil, growth, regeneration and ecological factors.
iv.  Advocates of intensive treatment hold that:-
(A)      The uniform system should be discarded in favor of strip system which entails intensive regeneration over a small area.
(B)       When the conditions are favorable.
(C)       A high-level technical skill and organization is needed for application of intensive treatment methods.
(D)      Intensive treatment has a clearcut advantage both from economic and cultural considerations.

(d) REGULARITY AND IRREGULARITY

Ø  There exists a considerable difference of opinion amongst foresters all over the world.

ü  Regularity

i.    The regular system generally implies an even-aged forest.
ii.   Clean cylindrical stems are produced, more valuable.
iii. If the old and mature crop is retained longer than needed, it is likely to hamper the growth of young crops and cause more damage to the seedling.

ü  Irregularity

i.    It leads to a general improvement of the soil.
ii.   More emphasis is laid on the development of every individual tree; more consequences.
iii. The ecology is disturbed to a lesser extent.
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SEE ALSO:  Nasturtium officinale

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