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| Last Updated::23/01/2019

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SELECTION OF CANDIDATE PLUS TREE, P&RE, JHARKHAND

Choosing the right seed source is one of the most important aspects of forest establishment. It can have huge implications for the early growth and survival of a plantation, and in later years on its productivity and wood quality. If the genetic quality of the planting stock is not correct from the outset, then there is little that can be done to improve a plantation other than costly replacement. Once planted, all subsequent operations and associated costs are applied to this material, it is therefore essential that it is capable of producing a good return if the plantation is to be economically viable. Clonal technology is one such viable option. Genetically improved clonal planting stock can contribute immensely to meet the demand of timber and wood based products. In the cloning process, selection of superior phenotypes or Candidate plus Trees (CPTs) is the most essential, critical and time consuming step.

Candidate plus tree are the individual trees of outstanding merits, initially selected on basis of phonotypical characters such as height, clean bole, diameter etc. Selection of the CPTs is the first step towards obtaining stock for developing clonal and seedling seed orchards of superior phenotypes. These superior phenotypes can be selected for their superiority in a single or multiple traits of interest in a single individual.  Selection of candidate plus tree must be done in selected stand to get best available superior tree.

Tree attributes to be taken into account during field assessment of plus-trees. Potential plus-trees are generally among the dominant individuals in a stand. Each trait is assessed relative to the average of neighboring trees. Some traits are more important than others, depending on species and the objectives of the tree improvement programme.

Attribute                    Considerations in selection

Stem straightness            A straight stem with little taper provides maximum volume and minimises Waste in timber production. Straightness is essential for veneer bolts.

Timber height                   This is the height to the first major fork. Good timber height maximises Potential for long lengths of usable timber.

Diameter                           Related to productivity and growth rates. An ideal tree will have superior volume increment and relatively little stem taper. For king Forks usually result from breakage or damage to the leading shoot. Repeated forking is often                                            due to a genetic pre-disposition in the tree (e.g., early bud burst in spring). A single fork is likely to be the result of frost damage or an insect pathogen.

Branch angle                   Branches at or close to horizontal orientation produce less knot wood  per unit length of the main stem.

Branch thickness           Heavy branching produces large knots which reduce the commercial grade and strength of timber.

Self-pruning                    Self-pruning is where lower branches abscise cleanly in low light conditions. Early self-pruning reduces the risk of stem infection and increases timber quality.

Crown dimensions         A large healthy crown is essential to ensure maximum photosynthetic potential. The crown should be evenly distributed.

Fluting                             Some trees produce irregular stem form, especially at the base. Any deviation from a concentric cross-section is undesirable.

Straight grain                  A uniform and linear grain produces the cleanest wood. Spiral grain  can often be noted in orientation of bark and produces wood that is more difficult to machine.

Disease                            Trees exhibit variation in resistance to many diseases. Life threatening diseases, those that effect productivity and those that disfigure the stem are all to be avoided.

Epicormics                      These are shoots that emerge from dormant buds along the stem in response to changes in light levels in the stand. Some species, such as oak, are especially susceptible to epicormics, after thinning operations

The selection criterions are as follows:
  • AGE: More than half the rotation age of tree must be selected.
  • GROWTH: Vigorous, healthy, superior in height and diameter compared to other trees must be selected. Dominant or co-dominant trees having more than 15 meter height.
  • STEM FORM: straight stem; cylindrical, circular in cross section without excessive taper; absence of spiral gain.
  • CROWN AND BRANCHING: Narrow to intermediate in width; not suppressed either from top or from sides; light and spreading branches, flaat or moderately ascending; good natural pruning
  • RESISTANCE: Tree must be free from any insect pest, fungal, bacterial,viral, mycoplasma nad physiological disorders.
  • FLOWERING AND FRUITING: Moderate to good

Final assessment of CPT would be based on measurements of height, diameter, clean bole and scoring given by silviculturist.

Plantation, Research and Evaluation circle of Jharkhand Forest Department undertook initial step to compile a document about availability of candidate plus tree in different regions to ease the primary work of maximum research projects. Survey of candidate plus tree was done in 25 different areas under lying in and between Ranchi and Jamshedpur district of the state in year 2015.

As a result, Overall 550 CPT’s were selected of total 52 tree species of Jharkhand in both the districts, out of which 11 species are found common in both the districts. List of species are mentioned in our glossary. All the trees which are selected for CPT survey have been marked in their respective areas so that seed collection could be done.