Conversion is defined as a change from one silvicultural system or one (set of) species to another. Thus, the concept of conversion involves a change in crop composition and/or silvicultural system by which the crops are regenerated and replaced by the new crops of distinctive form.
- Change in crop composition: It is often necessitated from any of the following reasons.
- Increasing yield from forest: Pine plantation in hills, Eucalyptus plantation in Sagarnath , Sissoo plantation in Kohalpur and in others in degraded Sal forest enrichment planting.
- To meet the demand of industries: Populus, Eucalyptus, Acacia, Bombax, Teak, etc.
- Change in the silvicultural system: Change from one silvicultural system to another is mainly for changing the characters of the crop and/or for changing the method of obtaining regeneration. Silvicultural systems are changed for the following reasons:
- Advantage of a particular System: Selection or selection cum improvement felling replaced by Uniform System. C.W.S. or Selection System replaced by C.W.R.
- Failure of an existing system: In case of Fir and Spruce, uniform system was changed to Selection System or Clear felling with reservation followed by artificial regeneration. In case of Teak uniform system was changed to Clear felling followed by natural or artificial regeneration.
- Advances in silvicultural knowledge and perfection of regeneration techniques
- Development of communication and increase in market demand
Techniques of Conversion
When a change in silvicultural system is desired, the entire area is not subjected to conversion at a time. Only a part of the forest is taken up under new system and rest is worked under old system where new areas are taken for conversion after completing conversion in the areas taken previously.
Pace or speed of conversion
The conversion period means the period in which conversion is to be done. The conversion period is very important consideration. When the conversion period is short the conversion proceeds with a fast speed on the other hand if conversion period is long, the conversion is slow.
The following considerations affect the decision about the length of conversion period:
- Sacrifice of immature crop (sacrifice is greater when conversion period short
- Proportion of the over mature growing stock with negative increment. Larger the proportion of over mature trees, the conversion period should be short, and vice versa.
- Hiatus between the age of first converted crop and the exploitable age at the end of conversion period
The decision on the length of conversion period should also take into account the age of first converted crop at the end of conversion period and compare it with exploitable age.
If the age of first converted crop is less than the exploitable age, there will be a hiatus at the end of conversion felling till the start of felling under the new system (uniform system).
Thus, the shorter the conversion period, the greater the hiatus. To overcome this difficulty, following two alternatives can be adopted.
- The conversion period should be so fixed that the first converted crop is mature at the end of conversion period.
- Part of the young immature crops should be retained as part of the future crops. These increase the mean age of converted crops and make them fit for exploitation earlier.